12th Standard CBSE Chemistry CBSE - study material, free online tests, previous year question papers, answer keys, topper answers, centum question paper, exam tips

12th Chemistry The d and f Block Elements Chapter Case Study Question with Answers CBSE - by users_admin - Jan 13, 2024 - View & Read

12th Chemistry Haloalkanes and Haloarenes Chapter Case Study Question with Answers CBSE - by users_admin - Jan 13, 2024 - View & Read

12th Chemistry Coordination Compounds Chapter Case Study Question with Answers CBSE - by users_admin - Jan 13, 2024 - View & Read

12th Chemistry Chemical Kinetics Chapter Case Study Question with Answers CBSE - by users_admin - Jan 13, 2024 - View & Read

12th Chemistry Biomolecules Chapter Case Study Question with Answers CBSE - by users_admin - Jan 13, 2024 - View & Read

12th Chemistry Amines Chapter Case Study Question with Answers CBSE - by users_admin - Jan 13, 2024 - View & Read

12th Aldehydes Ketones and Carboxylic Acids Chapter Case Study Question with Answers CBSE - by users_admin - Jan 13, 2024 - View & Read

12th Chemistry Alcohols Phenols and Ethers Chapter Case Study Question with Answers CBSE - by users_admin - Jan 13, 2024 - View & Read

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers Value Based Questions 5 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 31, 2021 - View & Read

1)
Gasoline is being used worldwide for running automobile, aeroplane etc. Due to the presence of nitrogen and sulphuric compounds in gasoline, the exhaust gases contain oxides of nitrogen and sulphur which are major pollutants in the environment in contrast, ethanol is a much cleaner fuel because it produces only CO₂ and Hp. Now answer the following questions:
(a) Besides being a cleaner fuel, what are the other advantages of using ethanol as a fuel in automobile?
(b) What are the disadvantages of using ethanol as a fuel? What are the value associated with its use?
2)
Miss Usha was asked to synthesize alcohol by acidic hydration of l-butene. She was unaware of the fact that the vessel she used had some coating of a metal, and in addition to alcohol, compound X was I isolated X forms bisulphate compound as well as 2, 4-dinitrophenylhydrazone. Separation of alcohol could be made by physical as well as by chemical methods.
(i) How are alcohol and Xformed?
(ii) Can alcohol and Xgive iodoform test?
(iii) Give different methods of separation?
(iv) What value did Miss. Usha lack?
3)
Mohan heard a lot of noise and weeping in nearby jhuggis he look courage and went to enquire what had happened. He found that some people has taken spurious alcohol containing methanol and were crying with pain and were complaining of loss of eyesight. He immediately hired an auto rickshaw and packed it with 4 persons who has consumed spurious alcohol.
(i) How does methanol in drinking alcohol cause problem?
(ii) What treatment might the doctors have undertaken to save the patients?
(iii) What message would you give to the person who consumed spurious alcohol?
4)
A teacher ordered ethanol for laboratory. She preferred denatured alcohol over absolute alcohol.
(i) Give reason for the decision taken by the teacher.
(ii) What value was kept in mind while taking the decision?

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes Value Based Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 31, 2021 - View & Read

1)
Trichloromethane or chloroform is a colorless oily liquid with a peculiar smell.It is sparingly soluble in water.The vapor when enhaled cause unconsciousness and therefore, it is used as an anesthetic.
Answer the following questions:
(i) What happens when chloroform is not protected from oxygen during its storage?
(ii) Why is the use of chloroform as an anesthetic has been reduced?
2)
D.D.T is one of the most powerful insecticides which is effective against the mosquitoes that spread malaria. Mukesh's mother wanted to buy D.D.T from the market to use at night to protect her family from mosquitoes. But Mukesh stopped his mother from purchasing D.D.T.
(a) How did Mukesh convince her mother for not using D.D.T at night?
(b) What values are attached to suggestion of Mukesh?

CBSE 12th Standard Chemistry Subject The p-Block Elements Value Based Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 31, 2021 - View & Read

1)
It is desired to produce ammonia gas from nitrogen and hydrogen according to the reaction:
\({ N }_{ 2 }(g)+3H_{ 2 }(g)\rightleftharpoons 2NH_{ 3 }(g)+Heat\)
Above reaction is exothermic and therefore, favored by low temperature. As a student of chemistry,which temperature would you suggest 350k or 750 k? Justify
2)
Nitrogen fertilizers are commonly used to promote the growth of plants and boost the crop yield.As a student of chemistry,can you suggest a farmer whether he should use excess nitrogen fertilizers to get maximum yield or not?
3)
Sulphuric acid is manufactured by Contact process.During the process,the following reaction takes place:
\({ 2SO }_{ 2 }(g)+O_{ 2 }(g)\rightleftharpoons 2SO_{ 3 }(g)\)
This reaction is favoured by high pressure, However,the pressure is not increase beyond 3 bar.As a students of chemistry how will you justify this?
4)
Account for the following:
(i) Iron on reaction with HCI forms FeCl₂ and not FeCI₃.
(ii) Draw structure of XeO_3.

CBSE 12th Standard Chemistry Subject Electrochemistry Value Based Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 31, 2021 - View & Read

1)
Manu and his father went to a shop to purchase a battery for their inverter. The shopkeeper showed them two types of batteries, one with lead plates and the other with cadmium plates. The battery with cadmium plates was more expensive than the lead battery. Manu's father wanted to purchase lead battery as it was cheaper.
After reading the above passage answer the following questions:
(a) As a student of chemistry, why would you suggest Manu's father buy the expensive cadmium plate battery. Give two reasons.
(b) What are the values associated with the above decision?
2)
Manoj went with his father to buy hinges for the door. The shopkeeper showed two types of hinges: normal iron hinges and the galvanized hinges. The normal hinges were costlier. Manoj's father opted for the cheaper normal iron hinges. Manoj suggested his father to buy galvanized hinges through these were costlier.
(a) what are the rationale for Manoj to buy galvanized hinges?
(b) What values are attached with this decision?
3)
Many food products are available in the market in tin cans. Jayant went to the market to buy tinned cans of a food product. The shopkeeper gave him a can which had scratches, though it had been recently packed. Jayant did not buy that can. How do you agree with Jayant's decision?

CBSE 12th Standard Chemistry Subject Solution Value Based Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 31, 2021 - View & Read

1)
Deep sea divers have been using the compressed air containing \({ N }_{ 2 }\) in addition to \({ O }_{ 2 }\) for breathing. When the sea diver breathes in compressed air at a depth, more \({ N }_{ 2 }\) dissolves in the blood and other body fluids than would dissolve at the surface because the pressure at the depth is far greater than surface atmospheric pressure. When the diver comes towards the surface, the pressure decreases and \({ N }_{ 2 }\) comes out of the body quickly forming bubbles in the blood stream which restrict blood flow and affect the transmission of nerve impulses. This results into a condition called 'the bends' which is dangerous and painful. To avoid this condition, professionals now use air diluted with helium. As a student of chemistry, can you analyse as to why helium is used?
2)
Common salt \((NaCI)\) and calcium chloride \((CaCI_{ 2 })\) are used to clear snow on the roads. The cost of sodium chloride and calcium chloride is almost the same. As a student of chemistry which salt would you prefer to purchase and why?
3)
Jagan went to Srinagar with his friend. He noticed that the taxi drivers always add ethylene glycol as a coolant in the radiator of the taxi and not water. He asked his driver, how much ethylene glycol he generally adds to the radiator. The taxi driver told him that he generally adds 30% ethylene glycol solution. On that day, the temperature of the valley was \(-10°C\) .
Answer the following questions:
(i) What is the role ethylene glycol when added to water?
(ii) Is the amount of ethylene glycol sufficient to avoid the freezing of water in car radiator when the temperature of the valley was \(-10°C\) ?
4)
Rekha observed that her mother placed shrinked or dried vegetables in water before cutting these for cooking. After sometime, these vegetables looked fresh.
Answer the following questions:
(i) Why did Rekha's mother place the shrinked or dried vegetables in water?
(ii) What is the name of the process used and define it.
(iii) Would the temperature increase accelerate the process or not?

CBSE 12th Standard Chemistry Subject Value Based Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 31, 2021 - View & Read

1)
Jagan went to Srinagar with his friend. He noticed that the taxi drivers always add ethylene glycol as a coolant in the radiator of the taxi and not water. He asked his driver, how much ethylene glycol he generally adds to the radiator. The taxi driver told him that he generally adds 30% ethylene glycol solution. On that day, the temperature of the valley was \(-10°C\) .
Answer the following questions:
(i) What is the role ethylene glycol when added to water?
(ii) Is the amount of ethylene glycol sufficient to avoid the freezing of water in car radiator when the temperature of the valley was \(-10°C\) ?
2)
Rekha observed that her mother placed shrinked or dried vegetables in water before cutting these for cooking. After sometime, these vegetables looked fresh.
Answer the following questions:
(i) Why did Rekha's mother place the shrinked or dried vegetables in water?
(ii) What is the name of the process used and define it.
(iii) Would the temperature increase accelerate the process or not?
3)
Manoj went with his father to buy hinges for the door. The shopkeeper showed two types of hinges: normal iron hinges and the galvanized hinges. The normal hinges were costlier. Manoj's father opted for the cheaper normal iron hinges. Manoj suggested his father to buy galvanized hinges through these were costlier.
(a) what are the rationale for Manoj to buy galvanized hinges?
(b) What values are attached with this decision?
4)
Sulphuric acid is manufactured by Contact process.During the process,the following reaction takes place:
\({ 2SO }_{ 2 }(g)+O_{ 2 }(g)\rightleftharpoons 2SO_{ 3 }(g)\)
This reaction is favoured by high pressure, However,the pressure is not increase beyond 3 bar.As a students of chemistry how will you justify this?
5)
D.D.T is one of the most powerful insecticides which is effective against the mosquitoes that spread malaria. Mukesh's mother wanted to buy D.D.T from the market to use at night to protect her family from mosquitoes. But Mukesh stopped his mother from purchasing D.D.T.
(a) How did Mukesh convince her mother for not using D.D.T at night?
(b) What values are attached to suggestion of Mukesh?

CBSE 12th Standard Chemistry Subject Value Based Questions 3 Mark Questions 2021 Part - II - by Archana Singh - Deoghar - May 31, 2021 - View & Read

1)
Deep sea divers have been using the compressed air containing \({ N }_{ 2 }\) in addition to \({ O }_{ 2 }\) for breathing. When the sea diver breathes in compressed air at a depth, more \({ N }_{ 2 }\) dissolves in the blood and other body fluids than would dissolve at the surface because the pressure at the depth is far greater than surface atmospheric pressure. When the diver comes towards the surface, the pressure decreases and \({ N }_{ 2 }\) comes out of the body quickly forming bubbles in the blood stream which restrict blood flow and affect the transmission of nerve impulses. This results into a condition called 'the bends' which is dangerous and painful. To avoid this condition, professionals now use air diluted with helium. As a student of chemistry, can you analyse as to why helium is used?
2)
Manu and his father went to a shop to purchase a battery for their inverter. The shopkeeper showed them two types of batteries, one with lead plates and the other with cadmium plates. The battery with cadmium plates was more expensive than the lead battery. Manu's father wanted to purchase lead battery as it was cheaper.
After reading the above passage answer the following questions:
(a) As a student of chemistry, why would you suggest Manu's father buy the expensive cadmium plate battery. Give two reasons.
(b) What are the values associated with the above decision?
3)
It is desired to produce ammonia gas from nitrogen and hydrogen according to the reaction:
\({ N }_{ 2 }(g)+3H_{ 2 }(g)\rightleftharpoons 2NH_{ 3 }(g)+Heat\)
Above reaction is exothermic and therefore, favored by low temperature. As a student of chemistry,which temperature would you suggest 350k or 750 k? Justify
4)
Nitrogen fertilizers are commonly used to promote the growth of plants and boost the crop yield.As a student of chemistry,can you suggest a farmer whether he should use excess nitrogen fertilizers to get maximum yield or not?
5)
Trichloromethane or chloroform is a colorless oily liquid with a peculiar smell.It is sparingly soluble in water.The vapor when enhaled cause unconsciousness and therefore, it is used as an anesthetic.
Answer the following questions:
(i) What happens when chloroform is not protected from oxygen during its storage?
(ii) Why is the use of chloroform as an anesthetic has been reduced?

CBSE 12th Standard Chemistry Subject Value Based Questions 3 Mark Questions 2021 Part - I - by Archana Singh - Deoghar - May 31, 2021 - View & Read

1)
Rekha observed that her mother placed shrinked or dried vegetables in water before cutting these for cooking. After sometime, these vegetables looked fresh.
Answer the following questions:
(i) Why did Rekha's mother place the shrinked or dried vegetables in water?
(ii) What is the name of the process used and define it.
(iii) Would the temperature increase accelerate the process or not?
2)
Many food products are available in the market in tin cans. Jayant went to the market to buy tinned cans of a food product. The shopkeeper gave him a can which had scratches, though it had been recently packed. Jayant did not buy that can. How do you agree with Jayant's decision?
3)
In thermal power stations, coal is burnt to produce steam for generation of electricity The smoke produced is passed through electrostatic precipitators before allowing it to escape into the atmosphere
4)
Account for the following:
(i) Iron on reaction with HCI forms FeCl₂ and not FeCI₃.
(ii) Draw structure of XeO_3.
5)
D.D.T is one of the most powerful insecticides which is effective against the mosquitoes that spread malaria. Mukesh's mother wanted to buy D.D.T from the market to use at night to protect her family from mosquitoes. But Mukesh stopped his mother from purchasing D.D.T.
(a) How did Mukesh convince her mother for not using D.D.T at night?
(b) What values are attached to suggestion of Mukesh?

CBSE 12th Standard Chemistry Subject Value Based Questions 5 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 31, 2021 - View & Read

1)
Molecular nitrogen is very little reactive chemically, During lightning discharge, atmospheric nitrogen and oxygen combine at high temperature to form nitric oxide (NO) which is then oxidised to nitrogen dioxide (NO₂), Ozone also combines with nitric oxide to form nitrogen dioxide. Both NO and NO₂ constitute smog which is very poisonous. It can cause burning sensation in the eyes and adversely affects respiratory system.
(i) What is the colour of nitrogen dioxide?
(ii) What happens when nitrogen dioxide is dissolved in water?
(iii) Suggest ways to check pollution caused by photochemical smog?
(iv) If Rachna would have decided to make people aware about it through street plays and posters, then what are the values shown by her?
2)
Gasoline is being used worldwide for running automobile, aeroplane etc. Due to the presence of nitrogen and sulphuric compounds in gasoline, the exhaust gases contain oxides of nitrogen and sulphur which are major pollutants in the environment in contrast, ethanol is a much cleaner fuel because it produces only CO₂ and Hp. Now answer the following questions:
(a) Besides being a cleaner fuel, what are the other advantages of using ethanol as a fuel in automobile?
(b) What are the disadvantages of using ethanol as a fuel? What are the value associated with its use?
3)
Miss Usha was asked to synthesize alcohol by acidic hydration of l-butene. She was unaware of the fact that the vessel she used had some coating of a metal, and in addition to alcohol, compound X was I isolated X forms bisulphate compound as well as 2, 4-dinitrophenylhydrazone. Separation of alcohol could be made by physical as well as by chemical methods.
(i) How are alcohol and Xformed?
(ii) Can alcohol and Xgive iodoform test?
(iii) Give different methods of separation?
(iv) What value did Miss. Usha lack?
4)
Mohan heard a lot of noise and weeping in nearby jhuggis he look courage and went to enquire what had happened. He found that some people has taken spurious alcohol containing methanol and were crying with pain and were complaining of loss of eyesight. He immediately hired an auto rickshaw and packed it with 4 persons who has consumed spurious alcohol.
(i) How does methanol in drinking alcohol cause problem?
(ii) What treatment might the doctors have undertaken to save the patients?
(iii) What message would you give to the person who consumed spurious alcohol?
5)
A teacher ordered ethanol for laboratory. She preferred denatured alcohol over absolute alcohol.
(i) Give reason for the decision taken by the teacher.
(ii) What value was kept in mind while taking the decision?

CBSE 12th Standard Chemistry Subject The p-Block Elements HOT Questions MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Cold ferrous sulphate solution on absorption of NO develops brown colour due to the formation of
2)
Of the following acids, the one which has the capability to form complex compound and also possesses oxidising and reducing properties is
3)
[Fe(H₂O)₅NO]²⁺ is a complex formed during the brown ring test for NO\(\overset{-}{3}\) ion. In this complex,
4)
Atoms in P₄ molecule of white phosphorus are arranged regularly in the following way
5)
The percentage of \(\pi\)-character in the orbitals forming P-P bonds in P₄ is

CBSE 12th Standard Chemistry Subject The p-Block Elements HOT Questions MCQ Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
An inorganic salt (A) is decomposed on heating to give two products (B) and (C). Compound (C) is a liquid at room temperature and is neutral to litmus while compound (B) is a colourless neutral gas. Compounds (A), (B) and (C) are
2)
With excess of CI₂, ammonia forms
3)
The gases produced in the reaction, Pb(NO₃)₂ \(\overset{\triangle}{\longrightarrow}\) and NH₄NO₃ \(\overset{\triangle}{\longrightarrow}\) are respectively
4)
The reddish brown coloured gas formed when nitric oxide is oxidised by air is
5)
Which statement is wrong for NO?

CBSE 12th Standard Chemistry Subject Amines HOT Questions Fill Up Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Surface Chemistry HOT Questions Fill Up Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
The conductance of an emulsion increases on adding common salt. What type of emulsion is it?
2)
What is syneresis or weeping of gels?
3)
Most effective electrolyte causing the coagulation of negatively charged AS₂S₃ solution is
(a) MgCl₂ b) KCl c) K₃ [Fe(CN)₄] d) Na₂SO₄.
4)
Silicate garden is developed by setting of colored ions in the void of silicates. It is a case of -----------------.
5)
What is purple of casius?

CBSE 12th Standard Chemistry Subject Chemistry in Everyday Life HOT Questions Fill Up Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Chemistry in Everyday Life HOT Questions Fill Up Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Give an example of a chemical substance which can act both as an antiseptic and disinfectant.
2)
What is the chemical name of antiseptic chloroxylenol?
3)
Which alkaloid is used to control hypertension?
4)
Which alkaloid is used to treat malaria?
5)
Identify the following :

CBSE 12th Standard Chemistry Subject Polymers HOT Questions Fill Up Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Polymers HOT Questions Fill Up Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
A patient tested to have gram positive bacterial infection. What type of antibiotic the physician might have prescribed to the patient ? Justify.

CBSE 12th Standard Chemistry Subject Biomolecules HOT Questions Fill Up Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Which of the following is not an α-amino acid? Histidine, trypsin, cysteine, proline.
2)
Write the structure of Zwitter ion formed from Alanine.
3)
Wreite the name and structure of the simplest amino acid which can show optical activity.
4)
How many hydrogen bonds are present between
(i) A and T
(ii) C and G in a double helix structure?

CBSE 12th Standard Chemistry Subject Biomolecules HOT Questions Fill Up Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
What are oligosaccharides ?
2)
What are the products of hydrolysis of sucrose?
3)
What are the products of hydrolysis of lactose?
4)
What type of bonding help in stabilising the \(\alpha\)-helix structure of proteins?

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids HOT Questions Fill Up Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids HOT Questions Fill Up Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Name the aldehyde which does not give Fehling’s soln. test.
2)
What makes acetic acid a stronger acid than phenol?
3)
Why HCOOH does not give HVZ (Hell Volhand Zelinsky) reaction but CH₃COOH does?
4)
Why pcc cannot oxidise methanol to methanoic acid and while KMnO₄ can?

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers HOT Questions Fill Up Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Write the IUPAC name of the product formed by the ctalytic reduction of Butanal.

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes HOT Questions Fill Up Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes HOT Questions Fill Up Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Coordination Compounds HOT Questions Fill Up Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Coordination Compounds HOT Questions Fill Up Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Which of the two is more stable K₄[Fe(CN)₆] or K₃[Fe(CN)₆]?

CBSE 12th Standard Chemistry Subject The d- and f- Block Elements HOT Questions Fill Up Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Calculate the spin only magnetic moment of Iron present in the following compound.
[Fe(H₂O)5NO]²⁺
2)
Among the ionic species Sc³⁺, Ce⁴⁺ and Eu²⁺ Which one is a good oxidizing agent?
3)
Why are Fe³⁺ and Cu²⁺ prominent in their aqueous solutions?
4)
CrO₃ is an acid anhydride. Explain.
5)
Though both Cr²⁺ and Mn³⁺ have d4 configuration, yet Cr²⁺ is reducing and Mn³⁺ is oxidizing. Explain Why?

CBSE 12th Standard Chemistry Subject The d- and f- Block Elements HOT Questions Fill Up Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
K₂PtCI₆ is a well known compound whereas corresponding Ni Compound is not known. State a reason for it.
2)
Explain why, Zn (II) salts are white while Mn (VII) are deep purple in colour?
3)
KMnO₄ is used in acidic medium quite frequently than in its aqueous or alkali for oxidizing purpose. Why?
4)
Give reasons:
i) Zr and Hf have identical sizes
ii) In the titration of FeSO₄ with KMnO₄ in the acidic medium dil. H2SO4 is used instead of dil HCl.

CBSE 12th Standard Chemistry Subject The p-Block Elements HOT Questions Fill Up Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers HOT Questions Fill Up Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Predict the product when sodium ethoxide and ethyl bromide are heated?
2)
Name the products obtain when anisole is treated with HI?
3)
Diethyl ether does not react with sodium. Why?
4)
Suggest a reason for the large difference in the boiling points of butanol and butanal, although they have same solubility in water.

CBSE 12th Standard Chemistry Subject The p-Block Elements HOT Questions Fill Up Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject General Principles and Processes of Isolation of Elements HOT Questions 1 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Which Substance is added to molten iron to remove sulphur impurity?
2)
What is “18:8 stainless steel”?
3)
During metallurgical process, in the extraction of metal, flux is added. Why?
4)
‘Reduction of a metal oxide is easier if the metal formed is in liquid state at the temperature of reduction. Why?
5)
Can Mg reduce Al₂O₃ and Al reduces MgO? State the conditions required for this reduction process.

CBSE 12th Standard Chemistry Subject Chemical Kinetics HOT Questions 1 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
How is half-life period related to initial concentration for a second order reaction ?
2)
The half life period of two samples are 0.1 and 0.4 seconds. Their initial concentrations are 200 and 50 mol L^-1 respectively. What is the order of reaction?
3)
What is the ratio of t_3/4 : t_1/2 for a first order reaction ?
4)
Higher molecularity reactions (viz. molecularity, 4 and above) are very rare. Why?
5)
Consider the reaction 2A + B ⟶ Products. When concentration of B alone was doubled, half life time does not change. When conc. of A alone doubled, the rate increases by two times . What are the units of K and what is the order of reaction?

CBSE 12th Standard Chemistry Subject General Principles and Processes of Isolation of Elements HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Out of C and CO, which is a better reducing agent at 673 K?
2)
Why copper matte is put in silica lined converter?
3)
What is the difference between reverberatory furnace & blast furnace.
4)
How does NaCN act as a depressant in preventing zinc from forming the froth? Explain.
5)
Why thermite process is not used for obtaining aluminum from bauxite.

CBSE 12th Standard Chemistry Subject The d- and f- Block Elements HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Explain why mercury (I) ion exists as \({ Hg }_{ 2 }^{ 2+ }\) ion while copper (I) ion exists as Cu⁺ ion.
2)
A mixed oxide of iron and chromium, FeO. Cr₂O₃ , is fused with sodium carbonate in presence of air to form a yellow coloured compound (A). On acidification, the compound (A) forms an orange coloured compound (B) which is a strong oxidizing agent. Identify
(i) the compounds (A) and (B)
(ii) Write balanced chemical equations for each step.
3)
(a) A blackish brown coloured solid 'A' when fused with alkali metal hydroxides in presence of air, produces a dark green coloured compound 'B', which on electrolytic oxidation in alkaline medium gives a dark purple coloured compound C. Identify A,B and C and write the reactions involved.
(b) What happens when an acidic solution of the green compound (B) is allowed to stand for some time ? Give the equation involved. What is this type of reaction called ?
4)
In what way do the d - block metals differ from alkali and alkaline earth metals ?

CBSE 12th Standard Chemistry Subject The d- and f- Block Elements HOT Questions 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Why in any transition series, melting points first increase and then decrease and also they show a dip in the middle ?
2)
Why hydrated copper sulphate is blue while anhydrous copper sulphate is white ?
3)
Atomic radius of Cu is greater than that of Cr but ionic radius of Cr²⁺ is greater than that of Cu²⁺ . Give suitable explanation.
4)
Give reasons for the following : Variations in the radii of transition elements are not as pronounced as those of representative elements.

CBSE 12th Standard Chemistry Subject Chemistry in Everyday Life HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Chemistry in Everyday Life HOT Questions 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Why is use of aspartame limited to cold foods and drinks?
2)
What are antihistamines ? Give two examples. Explain how ddo they act on the human body ?
3)
When a mixture of salicylic acid, acetic anhydride and acetic acid is refluxed, what is the product obtained and what is its use in everyday life ?
4)
Distinguish between a narrow spectrum and broad spectrum antibiotic.
5)
What is Salvarson ? To which class of drugs does it belong ? For what distance is it used?

CBSE 12th Standard Chemistry Subject Polymers HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Polymers HOT Questions 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Biomolecules HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Enumerate the reactions of D-glucose which cannot be explained by its open chain structure.
2)
How will you prove that all the carbon atoms of glucose are in straight chain?
3)
Enumerate two reactions of glucose which cannot be explained by its open chain structure.
4)
B-complex is an often prescribed Vitamin. What is complex about it ? What is its usefulness?
5)
What are anomers ? Give two points of difference between two anomer of glucose.

CBSE 12th Standard Chemistry Subject Biomolecules HOT Questions 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Where does the water present in the egg go after boling the egg ?

CBSE 12th Standard Chemistry Subject Amines HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Amines HOT Questions 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Name the reagents you will use to bring about the following conversions.
a. Ethane nitrile to ethanal
b. But-2-ene to ethanal

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids HOT Questions 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Fluorine is more electronegative than chlorine even then p-fluorobenzoic acid is a weaker acid than p-chlorobenzoic acid. Explain
2)
An organic compound with the molecular formula C₉H₁₀O forms 2, 4-DNP derivative, reduces Tollens' reagent and undergoes Cannizzaro reaction. On vigorous oxidation, it gives 1, 2-benzenedicarboxylic acid. Identify the compound.
3)
Name the reagents you will use to bring about the following conversions.
a. Ethane nitrile to ethanal
b. But-2-ene to ethanal

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers HOT Questions 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Explain the following
(a) Cyclohezanol is more soluble in water than 1-Hezanol
(b) Propane 1,3-diol is more soluble in the water than propan-1-ol
2)
Arreange the following in order of increasing boiling. State reason
CH₃CH₂CH₂OH, CH₃CH₂CH₂CH₃, CH₃CH₂OCH₂CH₃, CH₃CH₂CH2CHO
3)
Ethers are cleaved by acids not by bases. Why?

CBSE 12th Standard Chemistry Subject Coordination Compounds HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Coordination Compounds HOT Questions 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
How are octahedral complexes with high spin and low spin states formed? what is the condition of their formation?
2)
Give reason in two or three sentences only for the following:
The species [CuCl₄]^2- exists while [CuI₄]^2-does not?
3)
Dimethyl glyoxime is added to alcoholic solution of NiCl₂. When ammonium hydroxide is slowly added to it, a rosy red precipitate of a complex appears
(i) Give the structure of the complex showing hydrogen bonds.
(ii) Give oxidation state and hybridisation of central metal ion.
(iii) Identify whether it is paramagnetic or diamagnetic.
4)
Aqueous copper sulphate solution (blue in colour) gives
(i) a green precipitate with aqueous potassium fluoride, and
(ii) a bright green solution with aqueous potassium chloride. Explain these experimental results.

CBSE 12th Standard Chemistry Subject The p-Block Elements HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject The p-Block Elements HOT Questions 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
NH₃has a higher proton affinity than PH₃Explain.
2)
Bleaching of flowers by chlorine is permanent while that by sulphur dioxide is temporary. Explain.
3)
(a) You have the following substances : NH₃, O₂, Pt and H₂O. Write equations for the preparation of N₂O from these substances.
(b) Considering the fact that N₂ makes up about 79% of the atmosphere, why don't animals use the more abundant N₂ instead of O₂ for biological reactions.
4)
A certain element is a metalloid that forms an acidic oxide with the formula R₂O₅. Identify the element.
5)
(a) NCl₃ gets readily hydrolysed while NF₃ does not. Why?
(b) What kind of molecules show disproportionation reactions? Give one example of a compound each of nitrogen and phosphorus which show disproportionation reactions. Write chemical equation in each case.

CBSE 12th Standard Chemistry Subject Surface Chemistry HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Why is it necessary to remove carbon monoxide when ammonia is obtained by Haber's process?
2)
Critical temperatures of N₂, CO and CH₄ is 126, 134 and 190 K respectively. Arrange them in increasing order of adsorption on the surface of charcoal. Give reason.
3)
Explain the curdling of milk when it is sour.

CBSE 12th Standard Chemistry Subject Surface Chemistry HOT Questions 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Why the sun looks red at the time of setting ? Explain on the basis of colloidal properties.
2)
Addition of H₂ to acetylene gives ethane in presence of palladium but if BaSO₄ and quinoline or sulphur are also added, the product is ethane. Why ?
3)
SnO₂ forms a positively charged colloidal sol in acetic medium and a negatively charged sol in the basic medium. Why ? Explain.
4)
Explain the following giving reasons :
(i) Rate of physical adsorption decreases with rise of temperature.
(ii) Cause Brownian movement.
(iii) Colloidal particles scatter light.
5)
How does the rate of enzyme - catalysed reactions vary with (i) temperarture (ii) pH ? Represent diagrammatically.

CBSE 12th Standard Chemistry Subject Chemical Kinetics HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
A systematic plot of ln Keq versus 1/T for a reaction has been shown below: Prove that this reaction is exothermic
2)
Proposed mechanism for below given reaction :
2NO + Br₂ ⟶ 2NOBr is as follows
NO(g) + Br₂(g) ⟶ NOBr₂(g)
NOBr₂(g) + NO(g) ⟶ 2NOBr(g)
Find out the order w.r.t. NO (g)
3)
The rate for a reaction between the substance A and B is given by Rate = k[A]ⁿ [B]^m
On doubling the conc. of A and halving the conc. of B, find out the ratio of new rate to that of earlier rate of reaction.
4)
Decomposition of NH₃ (g) on surface of catalyst
2NH₃ ⟶ N₂ (g) + 3H₂(g)
Under low pressure follows first order kinetics while at high pressure it is zero order reaction. Why?
5)
In the reversible reaction.
Find out the rate of disappearance of NO₂

CBSE 12th Standard Chemistry Subject Chemical Kinetics HOT Questions 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
The rate of decomposition of ammonia is found to depend upon the concentration of NH3 according to the equation \(-\frac { d[{ NH }_{ 3 }] }{ dt } =\frac { { k }_{ 1 }[{ NH }_{ 3 }] }{ 1+{ k }_{ 2 }[{ NH }_{ 3 }] } \) What will be the order of reaction when
(i) concentration of NH₃is very high ?
(ii) Concentration of NH₃ is very low ?
2)
The rate law equation for the reaction A \(\longrightarrow\) B is found to be -\(\frac {d[A]}{dt} = k[A]^{1/2}\) If [A]0 were the initial concentration of A, derive expressions for
(i) rate constant in the intergrated form
(ii) half-life period of the reaction.
3)
While studying the decomposition of N₂O₅(g), it is observed that a plot of logarithm of its partial pressure versus time is linear. what kinetic parameter can be obtained from this ?
4)
Write the elementary steps of the reaction 2O₃ \(\rightleftharpoons \) 3O₂ and hence derive the rate law expression for this reaction. Comment on the order of reaction.
5)
For a first order reaction, derive expression for the degree of dissociation of the reactant in the expressional form.

CBSE 12th Standard Chemistry Subject Solution HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Why a person suffering from high blood pressure is advised to take minimum quantity of common salt ?
2)
To 500 cm³ of water, \(3.0\times { 10 }^{ -3 }\) kg of acetic acid is added. If 23% of acetic acid is dissociated, what will be the depression in freezing point ? K_f and density of water are 1.86 K kg mol^-1 and 0.997 g cm^-3respectively.
3)
75.2 g of phenol is dissolved in solvent of K_f = 14. If the depression in freezing point is 7K, find the % of phenol that dimerises ?
4)
An aqueous solution of 1.248 g of Barium chloride ( molar mass = 208.34 g mol^-1 ) in 100 g of water is found to boil at 100.0832⁰C. Calculate the degree of dissociation of BaCl₂ . K_b of water = 0.52 K kg mol^-1.
5)
The storage battery contains a solution of sulphuric acid 38 % by mass. At this concentration vant Hoff factor is 2.50. At what temperature will the battery condense freeze ? K_f for water = 1.86 K kg mol^-1.

CBSE 12th Standard Chemistry Subject Solution HOT Questions 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Why os camphor preferred as a solvent in finding the molecular mass of naphthalene by Rast method ?
2)
Two liquids A and B boil at 145^oC and 190^oC respectively. Which of them has higher vapour pressure at 80^oC ?
3)
Why a person suffering from high blood pressure is advised to take minimum quantity of common salt ?
4)
75.2 g of phenol is dissolved in solvent of K_f = 14. If the depression in freezing point is 7K, find the % of phenol that dimerises ?
5)
An aqueous solution of 1.248 g of Barium chloride ( molar mass = 208.34 g mol^-1 ) in 100 g of water is found to boil at 100.0832⁰C. Calculate the degree of dissociation of BaCl₂ . K_b of water = 0.52 K kg mol^-1.

CBSE 12th Standard Chemistry Subject The Solid State HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
A compound consisting of the monovalent ions A⁺,B^- crystallizes in the body-centred cubic lattice.(i)What is the of the compound? (ii)If one one of A⁺ions from the corner is replaced by a monovalent ion C⁺,what would be the simplest formula of the resulting compound?
2)
Calcium metal crystallize in a face-centred cubic lattice with edge length of 0.556nm.Calculate the density of the metal if contains (i)0.5% Frenkel defects(ii)0.2% Schottky defects.
3)
You are given marbles of diameter 10mm.They are to be placed such that their centres are lying in a square bound by four lines each of length 40mm.What will be the arrangement of marbles in a plane so that maximum number of marbles can be placed inside the area?Sketch the diagram and derive an expression for the number of marbles per unit area.
4)
Lithium iodide crystal has a face-centred cubic unit cell.If the edge length of the unit cell is 620pm,determine the ionic radius of I^-ion.
5)
Iron changes its crystal structure from body-centred to cubic close-packed structure when heated to 916⁰C.Calculate the ratio of the bcc crystal to that of ccp crystal,assuming that the metallic radius of the atom does not change.

CBSE 12th Standard Chemistry Subject The Solid State HOT Questions 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
If the atoms of an element have the radius r,then in a primitive cubic unit cell,calculate
(A) the length of the face diagonal
(B) the length of the body diagonal
2)
Out of NaCl and CsCl,which is more stable and why?
3)
In a crystal,Frenkel defect is not shown by alkali metal halides but silver halides show.Why?
4)
What is the arrangement of atoms in the lattice structure of diamond and give contribution of each C atom?
5)
Lithium borohydride,LiBH₄,crystallize in an orthorhombic system with 4 molecules per unit cell.The unit cell dimensions are: a=6.81\(\overset { 0 }{ A } \) ,b=4.43\(\overset{0}{A}\) and c=7.17\(\overset{0}{A}\).Calculate the density of the crystal.Take atomic mass of Li=7,B=11 and H=1 a.m.u.

CBSE 12th Standard Chemistry Subject Chemistry in Everyday Life HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Amines HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject The d- and f- Block Elements HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Which of the two \(Na^{ + }\) or \(Ag^{ + }\) is stronger Lewis acid and why?
2)
Which of two : cuprous chloride or cupric chloride is coloured and why?
3)
First ionisation energy of copper is higher than those of alkali metals, while second and third ionisation energies are lower. Explain.
4)
Zinc is a transition element and has many useful applications. The presence of zinc in trace amounts is essential in humans and many animals.
Answer the following questions:
(i) What is the role of zinc in the body of humans and animals?
(ii) A compound of zinc is used as a rodent poison. Name the compound.
(iii) Name the compound of zinc used in paints.
(iv) Is \(ZnSO_{ 4 }(aq)\) coloured or colourless?
5)
The decomposition of potassium chlorate \((KCIO_{ 3 })\) is a slow process. But the decomposition becomes fast in the presence of a black powder.
Answer the following:
(i) Why does the use of black powder make the decomposition fast?
(ii) What is black powder?
(iii) Can the black powder be used for all decomposition reactions?
(iv) Can you name the substance which can slow down the decomposition of \(H_{ 2 }O_{ 2 }\) ?

CBSE 12th Standard Chemistry Subject The p-Block Elements HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Why is \({ SO }_{ 2 }\) a better reducing agent in alkaline medium as compared to that in acidic medium? Explain?
2)
A colourless inorganic salt-(A) decomposes completely at 25⁰ C to give only two products (B), and (C) leaving no residue. The product (C) is a liquid at room temperature and neutral to moist litmus paper while the gas (B) is a neutral oxide. White phosphorus burns in excess of (B) to produce a strong white dehydrating agent. Write balanced equations for the reactions involved in the above process.

CBSE 12th Standard Chemistry Subject Surface Chemistry HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
(a) In which of the following does adsorption take place and why?
(i) Silica gel placed in the atmosphere saturated with water.
(ii) Anhydrous CaCl₂ placed in the atmosphere saturated with water.
(b) How does BF₃ act as a catalyst in industrial process?
(c) Give an example of shape-selective catalysis.

CBSE 12th Standard Chemistry Subject Chemical Kinetics HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
For the reaction, the energy of activation is 75KJ / mol. When a catalyst is added the reaction its energy of activation is lowered to 20KJ / mol. What is the effect of catalyst on the rate of reaction at 20⁰C.
2)
The gas phase decomposition of CH₃OCH₃ follows first order kinetics
CH₃OCH₃ ⟶ CH₄(g) + H₂(g) + CO(g)
The reaction is carried out in a constant volume container at 500⁰ C and has t_1/2 = 14.5 min. Initially only dimethyl ether is present at a pressure of 0.40 atm. What is the total pressure of the system after 12 min? Assume ideal behavior.
3)
A heterogenous reaction is carried out at 500 K. If the same reaction is carried out in the presence of catalyst at the same rate, the temperature requires is 400 K, calculate the activation energy of the reaction if the catalyst lowers the activation barrier by 20 KJ/mol.
4)
50% of the original amount of a reactant was added to the reaction mixture after 40 min. What % of the total amount will be present after 60 min, given that half life period of the reaction is 20 min.

CBSE 12th Standard Chemistry Subject Electrochemistry HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
What are the signs of \(\Delta G,K\) and \({ E° }_{ cell }\) for a spontaneous cell reaction?
2)
Consider the following half-cell reactions:
\({ Br }_{ 2 }+{ 2e }^{ - }\longrightarrow { 2Br }^{ - } \ \ E°=1.09V\\ { I }_{ 2 }+{ 2e }^{ - }\longrightarrow { 2I }^{ - } \ \ E°=0.54V\)
If \({ I }_{ 2 }\) and \({ Br }_{ 2 }\) are added to solution containing I M concentration of \({ I }^{ - }\) and \({ Br }^{ - }\) respectively.
(i) Write an equation for the overall cell reaction and \(E°\) of the cell.
(ii) Write the cell in which the reaction takes place, using Pt as the inert electrolyte for eacg electrode.
(iii) How will the increase in the concentration of \({ Br }^{ - }\) affect \({ E }_{ cell }\)?
3)
If change on the electron is \(1.60\times { 10 }^{ -19 }C\) and 96500 C deposit of 107.9 g of silver from its solution, calculate the value of Avogadro's number. (At. mass of Ag = 107.9 u)
4)
What pressure of H₂ would be required to make e.m.f. of the hydrogen electrode zero in pure water at 25°C?
5)
The standard reduction potential for \({ Cu }^{ 2+ }|Cu\) \(+0.34V\) . Calculate the reduction potential at \( pH=14\) for the above couple.\({ K }_{ sp }\) of \(Cu{ (OH) }_{ 2 }\) is \(1.0\times { 10 }^{ -19 }\).

CBSE 12th Standard Chemistry Subject Polymers HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Polymers HOT Questions 3 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Biomolecules HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Biomolecules HOT Questions 3 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
(a) A non reducing disaccharide 'A' on hydrolysis with dilute acid gives an equimolar mixture of D-( +)-glucose and D-(-)-Fructose.
\(A+{ H }_{ 2 }\quad \underrightarrow { HCl } { \quad C }_{ 6 }{ H }_{ 12 }{ O }_{ 6 }+{ C }_{ 6 }{ H }_{ 12 }{ O }_{ 6 }\)
[\(\alpha\)] = +66.5^ο +52.5^ο -92.4^o
Identify A.What is the mixture of D-( +)-glucose and D-(-)-Fructose known as ? Name the linkage that holds the two units in the disaccharide.
(b) \(\alpha\) -amino acids have relatively higher melting points than the corresponding halo acids. Explain.

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids HOT Questions 3 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Identify compounds (A)-(B) in the following reactions:

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Identify X,Y and Z
\(C3H7OH+ConcH2SO4\overset { 430-450k }{ \longrightarrow } X\overset { Br_{ 2 } }{ \longrightarrow } Y\overset { Excess }{ \longrightarrow } Z\)
3 Alc KOH
2)
a. R—Cl is hydrolysed to R—OH slowly but the reaction is rapid if a catalytic amount of KI is added to the reaction mixture.
b. What is formed if cylcopentanone is reduced with H2 /Pt . Give equation for the reaction.
3)
The treatment of alkyl chlorides with aq KOH leads to the formation of alcohols but in presence of alcoholic KOH, alkenes are the major products. Explain.

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers HOT Questions 3 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
(a) Why di-tert-butyl ether cannot be prepared by Williamson's synthesis?
(b) HI is a better reagent than HBr for cleavage of ether. Explain.
(c) The boiling points of ethers are lower than their corresponding isomeric alcohols. Explain.
2)
Give tha major products that are formed by heating each of following ethers with HI.
(i)

(ii)

(iii)

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
An alkyl halide X, of formula \({ C }_{ 6 }{ H }_{ 13 }Cl\) on treatment with potassium tertiary butoxide, gives the isomeric alkenes Y and Z \(\left( { C }_{ 6 }{ H }_{ 12 } \right) \). Both alkenes on hydrogenation give 2, 3-dimethylbutane. Predict the structures of X, Y and Z.
2)
An organic compound \({ C }_{ 8 }{ H }_{ 18 }\) on monochlorination gives a single monochloride.Write the structure of the hydrocarbon.
3)
Hydrolysis of 2-bromo-3-methylbutane \(\left( 2° \right) \) gives only 2-methyl1-2-butanol \(\left( 3° \right) \).Explain.

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes HOT Questions 3 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
An alkyl halide X, of formula \({ C }_{ 6 }{ H }_{ 13 }Cl\) on treatment with potassium tertiary butoxide, gives the isomeric alkenes Y and Z \(\left( { C }_{ 6 }{ H }_{ 12 } \right) \). Both alkenes on hydrogenation give 2, 3-dimethylbutane. Predict the structures of X, Y and Z.
2)
An organic compound \({ C }_{ 8 }{ H }_{ 18 }\) on monochlorination gives a single monochloride.Write the structure of the hydrocarbon.
3)
Hydrolysis of 2-bromo-3-methylbutane \(\left( 2° \right) \) gives only 2-methyl1-2-butanol \(\left( 3° \right) \).Explain.

CBSE 12th Standard Chemistry Subject Coordination Compounds HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Oxalic acid is commonly used to remove rust stains. Justify.
2)
Why is \({ K }_{ 4 }\left[ Fe{ \left( CN \right) }_{ 6 } \right]\) not toxic whereas KCN is highly toxic?

CBSE 12th Standard Chemistry Subject Coordination Compounds HOT Questions 3 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Why do the two complexes \({ PtCl }_{ 4 }.2{ NH }_{ 3 }\)and \({ PtCl }_{ 4 }.2KCL\)not give a precipitate of AgCl with \({ AgNO }_{ 3 }\)solution?
2)
Calcium dihydrogen salt of EDTA is used as an antidote for lead poisoning, why?
3)
\(Cu{ \left( OH \right) }_{ 2 }\)is soluble in \({ NH }_{ 4 }OH\)but not in NaOH solution.Why?
4)
Name a hexadentate ligand and write the formula of its complex with Co(III).Draw its structure.

CBSE 12th Standard Chemistry Subject General Principles and Processes of Isolation of Elements HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Cinnabar and Galena on roasting often give their respective metals but Zincblende does not. Explain.
2)
Explain the following
i. Carbon reduction process is not applied for reducing aluminium oxide to aluminium.
ii. Aq Sodium chloride cannot be used for the isolation of sodium by electrolytic reduction method.
iii. Thermite process is quite useful for repairing the broken parts of machines.
3)
The choice of a reducing agent in a particular case depends upon thermodynamic factor. How far do you agree with this statement? Explain?

CBSE 12th Standard Chemistry Subject General Principles and Processes of Isolation of Elements HOT Questions 3 Mark Questions 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
Metals donot occur in nature as nitrates. Why?
2)
Thermite process is quite useful for repairing broken parts of machines. Explain.
3)
The extraction of gold by leaching with NaCN involves both oxidation and reduction. Justify giving equation.
4)
In the metallurgy of copper partial roasting of sulphide ore is done. Why?
5)
Why is the reduction of a metal oxide easier if the metal formed is in liquid state at the temperature of reduction?

CBSE 12th Standard Chemistry Subject Surface Chemistry HOT Questions 5 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
A one - litre vessel contained a gas at 27^oC. 6 g of charcoal was introduced into it. The pressure of the gas fell down from 700 mm to 400 mm. Calculate the volume of the gas (at S.T.P) adsorbed per gram of charcoal. Density of charcoal sample used was 1.5 g cm^-3 .
2)
20% of surface sites are occupied by N₂ molecules. The density of surface sites is \(6.023\times { 10 }^{ 14 }\) cm^-2 and total surface area is 1000 cm² . The catalyst is heated to 300 K while N₂ is completely disorbed into a pressure of 0.001 atm and volume 2.46 cm³. Find the active sites occupied by each N₂ molecule.
3)
In an adsorption experiment, a graph between log (x/m) versus log P was found to be linear with a slope of 45^o. The intercept on the log (x/m) axis was found to be 0.310. Calculate the amount of the gas adsorbed per gram of charcoal under a pressure of 0.5 atmosphere.
4)
The volume of nitrogen gas v_m (measured at S.T.P) required to cover a sample of silica gel with a mono - molecular layer is 129 cm³g^-1 of gel. Calculate the surface area per gram of the gel if each nitrogen molecule occupies \(16.2\times { 10 }^{ -20 }{ m }^{ 2 }\).
5)
An emulsion is a colloidal dispersion in which both the dispersed phase and the dispersion medium are liquids. (The two liquids involved are otherwise immiscible).

CBSE 12th Standard Chemistry Subject Biomolecules HOT Questions 5 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

1)
How do expimers differ from anomers ?
2)
Glucose and fructose give the same osazone ? Explain.
3)
What forces are responsible for the stability of \(\alpha\) - helix ? Why is it named as 3.6₁₃ helix?
4)
The K_a and K_b values of \(\alpha\) - amino acids are very low. Explain.
5)
Write the structure of alanine at pH = 2 and pH = 10.

CBSE 12th Standard Chemistry Subject Amines HOT Questions 5 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 28, 2021 - View & Read

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes HOT Questions 5 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
Explain why alkyl halides are generally not prepared in the laboratory by free radical halogenation of alkanes.
2)
Explain why chorination of n-butane in presence of light at 298 K gives a mixture of 72% of 2-chlorobutane and 28 % of 1-chlorobutane.
3)
Wurtz reaction falils in case of tert-alkyl halides. Explain.
4)
(R)-2- Bromooctane reacts with NaSH to form (S)-2- octanethiol with inversion of configuration at the stereocentre.How can we obtain (R)-2 octanethiol from (R)-2-bromoctane?
5)
Benzene on reaction with HOCI in presence of an acid produces organic compound (A), (A) on treatment with NaNH₂/liq. NH₃ furnishes another organic compound (B). (B) on treatment with HBF₄ affords an organic compound (C) wich on heating with NaNO₂ gives organic compound (D). Identify (A), (B), (C) and (D).

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids HOT Questions 5 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
A compound with molecular formula, C₄H₁₀O₃ on acetylation with acetic anhydride gives a compound with molecular weight 190. Find out the number of hydroxyl groups present in the compound.
2)
A ketone A (C₄H₈O), which undergoes haloform reactions gives compound B on reduction. B on heating with sulphuric acid gives a compound C which forms mono-ozonide D.D on hydrolysis in presence of zinc dust gives only scetaldehyde E. Identify A, B ,C, D and E. Write the reactions involved.
3)
An organic compound (A) on treatment with ethyl alcohol gives a carboxylic acid (B) and compound (C). Hydrolysis of (C) under acidified conditions gives (B) and (D). Oxidation of (D) with KMnO₄ also gives (B). (B) on heating with Ca(OH)2 gives (E) having moleuclar formula C₃H₆O. (E) does not give TOllens'test and does not reduce Fehiling's solution but forms 2, 4-dinitrophenyhydrazone. Identify (A),(B),(C),(D) and (E).
4)
A compound A on oxidation gives B (C₂H₄O₂). A reacts with dil. NaOH and on subsequent heating forms C. C on catalytic hydrogenation gives D. Identify A, B, C, D and write down the reactions involved.
5)
An organic compound (A) having molecular formula, C₂H₄O reduces Tollens' reagent. Two moles of (A) react with AI(OC₂H₅)₃ to yield C₄H₈O₂ (B) which reacts with NH₃ to give C₂H₆O (C) and C₂H₅NO (D). Identify A,B,C and D.

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids HOT Questions 5 Mark Questions 2021 - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
Give reasons for the following:
(i) Oximes are more acidic than hydroxylamine.
(ii) Iodoform is obtained by the reaction of acetone with hypoiodite but with iodide ion.
(iii) Oxidation of tolune to benzaldehyde with CrO₃ is carried out presence of acetic anhydride and not in presence of H₂SO₄.
2)
Addition of Grignard reagents to dry ice followed by hydrolysis gives carboxylic acids while that of organolithium compounds under similar conditions gives ketones. Explain
3)
Tert-Butylbenzene does not give benzonic acid on oxidation acidic KMnO₄. Give reasons.
4)
Me₃CCH₂COOH is more acidic than Me₃SiCH₂COOH

CBSE 12th Standard Chemistry Subject Chemical Kinetics HOT Questions 5 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
The half time of first order decomposition of nitramide is 2.1 hour at 15^oC. NH₂NO₂(aq) \(\longrightarrow\) N₂O(g) + H₂O (I)
If 6.2 g of MH₂NO₂ is allowed to decompose, calculate
(i) time taken for NH₂NO₂ to decompose 99% and
(ii) volume of dry N₂O produced at this point, measured at STP.
2)
The time required for 10% completion of a first order reaction at 298 K is equal to that required for its 25% completion at 318 K. If the pre-exponential factor for the reaction is 3.56 \(\times 10 ^{9} s^{-1}\), calculate its rate constant at 318 K and also the energy of activation.
3)
For the reaction, N₂O₅(g) = 2 NO₂(g) + 0.5 O₂ (g), calculate the mole fraction of N₂O₅ (g) decomposed at a constant volume and temperature, if the initial presure is 600 mm Hg and the pressure at any time is 960 mm Hg. Assume ideal gas behaviour.
4)
Two first reactions proceed at the same rate at 15^oC when started with same initial concentration. The temperature coefficient of the first reaction is 2 while that of the second reaction is 3. What will be the ratio of the rates of these reactions at 55^oC ?
5)
When inversion of surcose is studied at pH = 5, the half-life period is always found to be 500 minutes irrespective of any initial concentration but when it is studied at pH = 6, the half-life period is found to be 50 minutes. Derive the rate law expression for the inversion of surcose.

CBSE 12th Standard Chemistry Subject Chemical Kinetics HOT Questions 5 Mark Questions 2021 - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
The time required for 10% completion of a first order reaction at 298 K is equal to that required for its 25% completion at 318 K. If the pre-exponential factor for the reaction is 3.56 \(\times 10 ^{9} s^{-1}\), calculate its rate constant at 318 K and also the energy of activation.
2)
For the reaction, N₂O₅(g) = 2 NO₂(g) + 0.5 O₂ (g), calculate the mole fraction of N₂O₅ (g) decomposed at a constant volume and temperature, if the initial presure is 600 mm Hg and the pressure at any time is 960 mm Hg. Assume ideal gas behaviour.
3)
At constant temperature and volume, X decomposes as 2 X (g) \(\longrightarrow\) 3 Y (g) + 2 Z (g). P_x is the partial pressure of X.

Observation No. Time (in minutes) P_x (in mm of Hg)

1 0 800

2 100 400

3 200 200

(i) What is the order of reaction with respect to X?
(ii) Find the time for 75% completion of the reaction.
(iii) Find the total pressure when pressure of X is 700 mm of Hg.
4)
The values of the rate constant for the decomposition of H₁ into H₂ and I₂ at different temperatures are given below :

T/K 633 667 710 738

10⁴k/M^-1s^-1 0.19 1.00 8.31 25.1

Draw a graph between In k against 1/T and calculate the values of Arrhenius parameters.
5)
The energy change accompanying the equilibrium reaction A \(\rightleftharpoons \) B is -33.0 kJ mol-1. Calculate
(i) Equilibrium constant K_c for the reaction at 300 K
(ii) Energy of activation forward and backward reaction (E_f and E_b) at 300 K. Given that Ef and Assume that pre-exponential factor is same for forward and backward reaction.

Observation No.	Time (in minutes)	P_x (in mm of Hg)
1	0	800
2	100	400
3	200	200

CBSE 12th Standard Chemistry Subject Electrochemistry HOT Questions 5 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
Three iron sheets have been coated separately with three metals (A, B and C) whose standard electrode potentials are given below :

Metal A B C Iron

E⁰_value - 0.46 - 0.66 V - 0.20 V - 0.44 V

Identify in which case rusting will take place faster when coating is damaged.
2)
Find the solubility product of Ag₂CrO₄ in water at 298 K if the e.m.f. of the cell Ag/Ag⁺ (saturated Ag₂CrO₄ soln.) || Ag⁺ (0.1 M)Ag is 0.164 V at 298 K.
3)
A cell, Ag | Ag⁺ || Cu²⁺ | Cu, initially contains 1 M Ag⁺ and 1 M Cu²⁺ ions. Calculate the change in cell potential after the passage of 9.65 A of current for 1h.
4)
Two students use same stock solution of ZnSO₄ and a solution of CuSO₄ . The e.m.f. of one cell is 0.03 V higher than the other. The concentration of CuSO₄ in the cell with higher e.m.f. value is 0.5 M. Find out the concentration of CuSO₄ in the other cell (2.303 RT/F = 0.06)
5)
EMF of Daniell cell was found using different concentrations of Zn²⁺ ion and Cu² ion. A graph was then plotted between E_cell and \(\log { \frac { \left[ { Zn }^{ 2+ } \right] }{ \left[ { Cu }^{ 2+ } \right] } } \) . The plot was found to be linear with intercept on E_cell axis equal to 1.10 V. Calculate E_cell for Zn | Zn²⁺ (0.1 M) || Cu²⁺ (0.01 M) | Cu.

CBSE 12th Standard Chemistry Subject Electrochemistry HOT Questions 5 Mark Questions 2021 - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
If E⁰₁, E⁰₂ and E⁰₃ are the standard electrode potentials for \(Fe/{ Fe }^{ 2+ },{ Fe }^{ 2+ }/{ Fe }^{ 3+ }\) and \(Fe/{ Fe }^{ 3+ }\) electrodes respectively, derive a relation between E⁰₁, E⁰₂ and E⁰₃.
2)
The following electrochemical cell has been set up
\(Pt(1)|{ Fe }^{ 3+ },{ Fe }^{ 2+ }(a=1)|{ Ce }^{ 4+ },{ Ce }^{ 3+ }(a=1)|Pt(2)\)
\({ E }^{ 0 }\left( { Fe }^{ 3+ }/{ Fe }^{ 2+ } \right) =0.77V;{ E }^{ 0 }\left( { Ce }^{ 4+ }/{ Ce }^{ 3+ } \right) =1.61V\)
If an ammeter is connected between the two platinum electrodes, predict the direction of flow of current. Will the current increase or decrease with time ?
3)
Tarnished silver contains Ag₂ S. Can this tarnish be removed by placing tarnished silver ware in an aluminium pan containing an inert electrolytic solution such as NaCl ? The standard electrode potential for the half reactions are : For \({ Ag }_{ 2 }S(s)+{ 2e }^{ - }\longrightarrow 2Ag(s)+{ S }^{ 2- },\) it is - 0.71 V and for \({ Al }^{ 3+ }+{ 3e }^{ - }\longrightarrow Al(s)\), it is - 1.66 V
4)
Three iron sheets have been coated separately with three metals (A, B and C) whose standard electrode potentials are given below :

Metal A B C Iron

E⁰_value - 0.46 - 0.66 V - 0.20 V - 0.44 V

Identify in which case rusting will take place faster when coating is damaged.
5)
Calculate the standard electrode potential of Cu⁺/Cu half cell. Given that the standard reduction potentials of Cu²⁺/Cu and Cu²⁺/Cu⁺ are 0.337 V and 0.153 V respectively.

CBSE 12th Standard Chemistry Subject HOT Questions MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
An inorganic salt (A) is decomposed on heating to give two products (B) and (C). Compound (C) is a liquid at room temperature and is neutral to litmus while compound (B) is a colourless neutral gas. Compounds (A), (B) and (C) are
2)
The gases produced in the reaction, Pb(NO₃)₂ \(\overset{\triangle}{\longrightarrow}\) and NH₄NO₃ \(\overset{\triangle}{\longrightarrow}\) are respectively
3)
Which statement is wrong for NO?
4)
A gaseous substance dissolves in water giving a pale blue solution which decolourises KMnO₄ and oxidises KI to I₂ . Gaseous substance is
5)
Nitric acid can be obtained from ammonia via the formation of the intermediate compounds

CBSE 12th Standard Chemistry Subject HOT Questions 1 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
How is half-life period related to initial concentration for a second order reaction ?
2)
What is the ratio of t_3/4 : t_1/2 for a first order reaction ?
3)
Consider the reaction 2A + B ⟶ Products. When concentration of B alone was doubled, half life time does not change. When conc. of A alone doubled, the rate increases by two times . What are the units of K and what is the order of reaction?

CBSE 12th Standard Chemistry Subject HOT Questions 1 Mark Questions 2021 Part - II - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
Gelatin is general added to ice-creams. Why?
2)
The half life period of two samples are 0.1 and 0.4 seconds. Their initial concentrations are 200 and 50 mol L^-1 respectively. What is the order of reaction?

CBSE 12th Standard Chemistry Subject HOT Questions 1 Mark Questions 2021 Part - I - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
Gelatin is general added to ice-creams. Why?
2)
Why artificial rain can be caused by throwing common salt on the clouds?

CBSE 12th Standard Chemistry Subject HOT Questions 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
Lithium borohydride,LiBH₄,crystallize in an orthorhombic system with 4 molecules per unit cell.The unit cell dimensions are: a=6.81\(\overset { 0 }{ A } \) ,b=4.43\(\overset{0}{A}\) and c=7.17\(\overset{0}{A}\).Calculate the density of the crystal.Take atomic mass of Li=7,B=11 and H=1 a.m.u.
2)
Why a person suffering from high blood pressure is advised to take minimum quantity of common salt ?
3)
Write the elementary steps of the reaction 2O₃ \(\rightleftharpoons \) 3O₂ and hence derive the rate law expression for this reaction. Comment on the order of reaction.
4)
Addition of H₂ to acetylene gives ethane in presence of palladium but if BaSO₄ and quinoline or sulphur are also added, the product is ethane. Why ?
5)
Why copper matte is put in silica lined converter?

CBSE 12th Standard Chemistry Subject HOT Questions 2 Mark Questions 2021 Part - II - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
Iron changes its crystal structure from body-centred to cubic close-packed structure when heated to 916⁰C.Calculate the ratio of the bcc crystal to that of ccp crystal,assuming that the metallic radius of the atom does not change.
2)
What is the role of ZnCl₂ in a dry cell?
3)
The rate for a reaction between the substance A and B is given by Rate = k[A]ⁿ [B]^m
On doubling the conc. of A and halving the conc. of B, find out the ratio of new rate to that of earlier rate of reaction.
4)
How does NaCN act as a depressant in preventing zinc from forming the froth? Explain.
5)
(a) NC1₃ get hydrolysed to form NH₃ and HOCI while PCI₃ on hydrolysis gives H₃PO₃ and HCI. Explain why ?
(b) SOCI₂ can act as a weak acid as well as a weak base. Explain.

CBSE 12th Standard Chemistry Subject HOT Questions 2 Mark Questions 2021 Part - I - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
What is the arrangement of atoms in the lattice structure of diamond and give contribution of each C atom?
2)
Lithium iodide crystal has a face-centred cubic unit cell.If the edge length of the unit cell is 620pm,determine the ionic radius of I^-ion.
3)
Two liquids A and B boil at 145^oC and 190^oC respectively. Which of them has higher vapour pressure at 80^oC ?
4)
Zn rod weighing 25 g was kept in 100 mL of 1M copper sulphate solution. After certain time interval, the molarity of Cu²⁺ was found to be 0.8 M. What is the molarity of SO₄^2- in the resulting solution and what should be the mass of Zn rod after cleaning and drying ?
5)
While studying the decomposition of N₂O₅(g), it is observed that a plot of logarithm of its partial pressure versus time is linear. what kinetic parameter can be obtained from this ?

CBSE 12th Standard Chemistry Subject HOT Questions 3 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
Why is melting point of a substance used as criterion for testing the purity of a substance?
2)
Crude copper containing Fe and Ag as contaminations was subjected to electro refining by using a current of 175 A for 6.434 min. The mass of anode was found to decrease by 22.260 g, while that of cathode was increased by 22.011 g. Estimate the % of copper, iron and silver in crude copper.

CBSE 12th Standard Chemistry Subject HOT Questions 3 Mark Questions 2021 Part - II - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
If vapour pressure of liquid A is greater than the vapour pressure of liquid B, then boiling point of A is lower than that of liquid B. Do you agree with the statement? Explain.
2)
A heterogenous reaction is carried out at 500 K. If the same reaction is carried out in the presence of catalyst at the same rate, the temperature requires is 400 K, calculate the activation energy of the reaction if the catalyst lowers the activation barrier by 20 KJ/mol.
3)
The extraction of gold by leaching with NaCN involves both oxidation and reduction. Justify giving equation.
4)
Explain the following
i. Carbon reduction process is not applied for reducing aluminium oxide to aluminium.
ii. Aq Sodium chloride cannot be used for the isolation of sodium by electrolytic reduction method.
iii. Thermite process is quite useful for repairing the broken parts of machines.

CBSE 12th Standard Chemistry Subject HOT Questions 3 Mark Questions 2021 Part - I - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
Why water cannot be separated completely from ethanol by fractional distillation?
2)
The standard reduction potential for \({ Cu }^{ 2+ }|Cu\) \(+0.34V\) . Calculate the reduction potential at \( pH=14\) for the above couple.\({ K }_{ sp }\) of \(Cu{ (OH) }_{ 2 }\) is \(1.0\times { 10 }^{ -19 }\).
3)
A heterogenous reaction is carried out at 500 K. If the same reaction is carried out in the presence of catalyst at the same rate, the temperature requires is 400 K, calculate the activation energy of the reaction if the catalyst lowers the activation barrier by 20 KJ/mol.

CBSE 12th Standard Chemistry Subject HOT Questions 5 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
The following electrochemical cell has been set up
\(Pt(1)|{ Fe }^{ 3+ },{ Fe }^{ 2+ }(a=1)|{ Ce }^{ 4+ },{ Ce }^{ 3+ }(a=1)|Pt(2)\)
\({ E }^{ 0 }\left( { Fe }^{ 3+ }/{ Fe }^{ 2+ } \right) =0.77V;{ E }^{ 0 }\left( { Ce }^{ 4+ }/{ Ce }^{ 3+ } \right) =1.61V\)
If an ammeter is connected between the two platinum electrodes, predict the direction of flow of current. Will the current increase or decrease with time ?
2)
At constant temperature and volume, X decomposes as 2 X (g) \(\longrightarrow\) 3 Y (g) + 2 Z (g). P_x is the partial pressure of X.

Observation No. Time (in minutes) P_x (in mm of Hg)

1 0 800

2 100 400

3 200 200

(i) What is the order of reaction with respect to X?
(ii) Find the time for 75% completion of the reaction.
(iii) Find the total pressure when pressure of X is 700 mm of Hg.
3)
Although both allyl alcohol and 1-propanol are primary alcohols,they can still be distinguished by Lucas reagent. Explain how?

Observation No.	Time (in minutes)	P_x (in mm of Hg)
1	0	800
2	100	400
3	200	200

CBSE 12th Standard Chemistry Subject HOT Questions 5 Mark Questions 2021 Part - II - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
Three iron sheets have been coated separately with three metals (A, B and C) whose standard electrode potentials are given below :

Metal A B C Iron

E⁰_value - 0.46 - 0.66 V - 0.20 V - 0.44 V

Identify in which case rusting will take place faster when coating is damaged.
2)
When inversion of surcose is studied at pH = 5, the half-life period is always found to be 500 minutes irrespective of any initial concentration but when it is studied at pH = 6, the half-life period is found to be 50 minutes. Derive the rate law expression for the inversion of surcose.
3)
Explain why chorination of n-butane in presence of light at 298 K gives a mixture of 72% of 2-chlorobutane and 28 % of 1-chlorobutane.
4)
Me₃CCH₂COOH is more acidic than Me₃SiCH₂COOH

CBSE 12th Standard Chemistry Subject HOT Questions 5 Mark Questions 2021 Part - I - by Archana Singh - Deoghar - May 27, 2021 - View & Read

1)
Tarnished silver contains Ag₂ S. Can this tarnish be removed by placing tarnished silver ware in an aluminium pan containing an inert electrolytic solution such as NaCl ? The standard electrode potential for the half reactions are : For \({ Ag }_{ 2 }S(s)+{ 2e }^{ - }\longrightarrow 2Ag(s)+{ S }^{ 2- },\) it is - 0.71 V and for \({ Al }^{ 3+ }+{ 3e }^{ - }\longrightarrow Al(s)\), it is - 1.66 V
2)
For the reaction, N₂O₅(g) = 2 NO₂(g) + 0.5 O₂ (g), calculate the mole fraction of N₂O₅ (g) decomposed at a constant volume and temperature, if the initial presure is 600 mm Hg and the pressure at any time is 960 mm Hg. Assume ideal gas behaviour.
3)
Explain the following in one or two sentences
(i) Displacement of cyanic and amide ion is never observed in nucleophilic substitution reactions.
(ii) RCI is hydrolysed to ROH slowly but the reaction is rapid if a catalytic amount of KI is added to the reaction mixture.
4)
2,2-Dimethyloxirane can be cleaved by acid (H⁺).Write its mechanism.

CBSE 12th Standard Chemistry Subject Coordination Compounds Ncert Exemplar 5 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Using crystal field theory, draw energy level diagram, write electronic configuration of the central metal atom/ion and determine the magnetic moment value in the following :
(i) \([CoF_6]^{3-}, [Co(H_2O)_6]^{2+},[Co(CN)_6]^{3-}\)
(ii) \([FeF_6]^{3-}, \ [Fe(H_2O)_6]^{2+}, [Fe(CN)_6]^{4-}\).
2)
Using valence bond theory, explain the following in relation to the complexes given below :
\([Mn(CN)_6]^{3-}, [Co(NH_3)_6]^{3+}, [Cr(H_2O)_6]^{3+}, [FeCl_6]^{4-}\)
(i) Type of hybridisation
(ii) Inner or outer orbital complex.
(iii) Magnetic behaviour.
(iv) Spin only magnetic moment value.
3)
CoSO₄Cl.5 NH₃exists in two isomeric forms 'A' and 'B' gives white precipitate with BaCl₂but does not react with AgNO₃. Answer the following questions.
(i) Identify 'A' and 'B' and write their structure formulas.
(ii) Name the type of isomerism involved
(iii) Give the IUPAC name of 'A' and 'B'.
4)
What is the relationship between observed colour of the complex and the wavelength of light absorbed by the complex ?
5)
Why are different colours observed in octahedral and tetrahedral complexes for the same metal and same ligands ?

CBSE 12th Standard Chemistry Subject The p-Block Elements Ncert Exemplar 5 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
An amorphous solid 'A' burns in air to form a gas 'B' which turns lime water milky. The gas is also produced as a by-product during roasting of sulphide ore. This gas decolourises acidified aqueous KMnO₄solution and reduces Fe³⁺ to Fe²⁺Identify the solid "A" and the gas "B" and write the reactions involved.
2)
On heating, lead (II) nitrate gives a brown gas 'A'. The gas 'A' on cooling changes to colourless solid 'B'. Solid 'B' on heating with NO changes to a blue solid 'C'. Identiy 'A', 'B' and 'C' and also write reactions involved and draw the structures of 'B' and 'C'.
3)
On heating compound(A) gives a gas (B) which is a constituent of air. This gas when treated with 3 mol of hydrogen (H₂) in the presence of a catalyst gives another gas (C) which is basic in nature. Gas C on further oxidation in moist condition gives a compound (D) which is a part of acid rain. Identify compounds (A) to (D) and also give necessary equations of all the steps involved.
4)
On heating compound (A)gives a gas (B)which is a constituent of air.This gas when treated with 3 mol of hydrogen (H₂) in the presence of a catalyst gives another gas (C) which is basic in nature. Gas C on further oxidation in moist condition gives gives a compound (D) which is a part of acid rain. Identify compounds (A) to D and also give necessary equations of all the steps involved.
5)
An amorphous solid A burns in air to form a gas B which turns lime water milky. The gas is also produced as a byproduct during roasting of sulphide ore. This gas decolourises acidified aqueous KMnO₄ solution and reduces Fe ³⁺ to Fe²⁺. Identify the solid 'A' and the gas 'B ' and write the reactions involved.

CBSE 12th Standard Chemistry Subject Chemistry in Everyday Life Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
How are receptor proteins located in the cell membrance?
2)
What is the basic difference between antiseptics and disinfectants?
3)
What is the difference between saccharin and saccharic acid?
4)
What are fillers and what role do they play in soap?
5)
Give reasons for the following:
(i) Use of aspartame limited to cold foods and drinks?
(ii) sometimes foaming is seen in river water near the place, where sewage water is poured after treatment?

CBSE 12th Standard Chemistry Subject Chemistry in Everyday Life Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Hair shampoos belong to which class of synthetic detergent ?
2)
How does the branching of hydrocarbon chain of synthetic detergents affect their biodegradability?
3)
What are antagonistic drugs?
4)
If soap has high alkali content it irritates skin. How can the amount of excess alkali be determined? What can be the source of excess alkali?

CBSE 12th Standard Chemistry Subject Polymers Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
What is the role of benzoyl peroxide in addition polymerisation of alkenes ?
2)
A natural linear polymer of 2-methyl-1,3-butadiene becomes hard on treatment with sulphur between 373 to 415K and -S-S- bonds are formed between chains.Write the structure of the product of this treatment?
3)
Out of chain growth polymerisation and step growth polymerisation, in which type will you place the following: (A)_m + (A)_m(A)_n or (A A)_m+n
4)
Why are rubbers called a elastomer?
5)
can enzyme be called a polymer?

CBSE 12th Standard Chemistry Subject Biomolecules Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Which moieties of nuclosides are involved in the formation of phophodiester linkages present in dinucleotides ? what does the would diester in the name of linkage indicate ? which acid is involved in the formation of this linkage ?
2)
What are glycosidic linkages ? In which type of biomolecules are they present ?
3)
Which monosaccharide units are present in starch, cellulose and glycogen and which linkages link these units ?
4)
How do enzymes help a substrate to be attacked by the reagent effectively ?

CBSE 12th Standard Chemistry Subject Biomolecules Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Name the sugar present in milk. How many monosaccharide units are present in it ? What are the such oligosaccharides called ?
2)
How do you explain the presence of all the six carbon atoms in glucose in a straight chain ?
3)
Name the linkage connecting monosaccharide units in polysachharides.
4)
Under what conditions glucose is converted to gluconic and saccharic acid ?

CBSE 12th Standard Chemistry Subject Amines Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
A primary amine, RNH₂ can be reacted with CH₃-X to get secondary amine, R-NHCH₃ but the only disadvantage is that \({ 3 }^{ \circ }\) amine and quaternary ammonium salts are also obtained as side products. Can you suggest a method where RNH₂ forms only \({ 2 }^{ \circ }\) amine
2)
Write the IUPAC name of the following compounds:
\({ H }_{ 3 }C-\underset { \overset { | }{ { H }_{ 3 }C } }{ N } -\overset { \overset { { CH }_{ 3 } }{ | } }{ \underset { \overset { | }{ { C }_{ 2 }{ H }_{ 5 } } }{ C } } -{ CH }_{ 2 }{ CH }_{ 3 }\)
3)
What is diazotisation? Why are benzenediazonium salts more stable than alkanediazonium salts?
4)
In the following sequence of reactions, write the structures of the compounds P, Q and R.
\(\ P\overset { B{ r }_{ 2 } }{ \underset { Sn/HCI }{ \longrightarrow } } Q\overset { (i)\ { NaNO }_{ 2 }\ /\ HCI,\ 273-278K }{ \underset { (ii)\ { H }_{ 2 }O/{ H }_{ 3 }{ PO }_{ 2 } }{ \longrightarrow } } R\overset { { KMnO }_{ 4 }\ /\ { OH }^{ - } }{ \longrightarrow } o-Bromobenzoic\ acid\)
5)
Identify A and B in the following reaction.

CBSE 12th Standard Chemistry Subject Amines Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
What is the rol of HNO₃ in the nitrating mixture used for nitration of benzene?
2)
Why is NH₂ group of aniline acetylated before carrying out nitration?
3)
What is the product when C₆H₅CH₂NH₂ reacts with NHO₂?
4)
What is the best reagent to convert nitrile to primary amine?
5)
What is Hinsberg reagent?

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Explain the mechanism of a nucleophilic attack on the carbonyl group of an aldehyde or a ketone ?
2)
Write chemical equations when :
(i) Acetone reacts with ethanol.
(ii) Ethanal reacts with HCN.
(iii) Acetone reacts with HCN.
(iv) Acetone reacts with NaHSO₃.
(v) Ethanal reacts with NaHSO₃
3)
State reasons for the following :
(i) Monochloroethanoic acid has a higher pK_a value than dichloroethanoic acid.
(ii) Ethanoic acid is a weaker acid than benzoic acid.
4)
Can Gattermann-Koch reaction be considered simular to Friedel-Crafts acylation? Discuss
5)
Ethyl benzene is generally prepared by acetylation of benzene followed by the reduction and not by direct alkylation. Think of a possible reason.

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Give simple chemical tests to distinguish between the following pairs of compounds.
(i) Pentan-2-one and Pentan-3-one
(ii) Ethanal and Propanal
2)
Benzaldehyde can be obtained from benzal chloride. Write reactions obtaining benzalchloride and then benzaldehyde from it.
3)
Compound 'A' was prepared by oxidation 'B' with alkaline KMnO₄. Compound 'A' on reduction with lithium aluminium hydride gets converted back to compound 'B'. When compound 'A' is heated with compound B in the presence of H₂SO₄ it produces fruitly smell of compound C to which family the compounds 'A', 'B' and 'C' belong to?
4)
Alkenes \(\diagdown \quad \quad \quad \ \ \diagup \\( \ C = C \ ) \\ \diagup \quad \quad \quad \ \ \diagdown\) and carbonyl compounds \(\diagdown \\( \ C = O \quad ) \\ \diagup\), both contain a \(\pi\) - bond but alkenes show electrophilic addition reactions whereas carbonyl compounds show nucleophilic addition reactions. Explain.
5)
When liquid 'A' is treated with a freshly prepared ammoniacal silver nitrate solution, it gives bright silver mirror. The liquid forms a white crystalline the solid on treatment with sodium hydrogensulphite. Liquid 'B' also forms a white crystalline solid with sodium hydrogensulphite but it does not give test with ammoniacal silver nature. Which of the two liquids is aldehyde? Write the chemical equations of these reactions also.

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Name the enzmes and write the reactions involved in the preparation of ethanol from sucrose by fermentation.
2)
How can propan-2-one be converted into tert-butly alcohol?
3)
Write the structures if the isomers of alcohols with molecular formula C₄H₁₀O. Which of these exhibits optical activity?
4)
Explain why is OH group in phenols more strongly held as compound to OH group in alcohols.
5)
Explain why nucleophilic substitution reactions are not very common in phenols.

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
What is the structure abd IUPAC name of glycerol?
2)
Name the factors responsible for the solubility of alcohols in water.
3)
Suggest a reagent for conversion of ethanol to ethanal.
4)
Suggest a reagent for conversion of ethanol to ethanoic acid.
5)
Out of 0-nitrophenol and p-nitrophenol, which volatile? Explain.

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Which of the compounds will react faster in S_N¹reaction with the ^-OH ion?
CH₃-CH₂-Cl or C₆H₅-CH₂-Cl
2)
Why iodoform has appreciable antiseptic property?
3)
Discuss the role of Lewis acid in the preparation of aryl bromides and chlorides in the dark.

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
What are the IUPAC names of the insecticide DDT and benzene hexachloride? Why is their use banned in india and other countries?
2)
Allyl chloride is hydrolysed more readily than n-propyl chloride. Why?
3)
Why it is necessary to avoid even traces of moisture during the use of a Grignard reagent?

CBSE 12th Standard Chemistry Subject Coordination Compounds Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Why are different colours observed in octahedral and tetrahedral complexes for the same metal and same ligands?
2)
CoSO₄Cl. 5NH₃ exists in ywo isomeric forms 'A' and 'B' . Isomer 'A' reacts with AgNO₃ to give white precipitate, but does not react with BaCl₂. Isomer 'B' gives white precipitate with BaCl₂ but does not react with AgNO₃. Answer the following questions.
(i) Identify 'A' and 'B' and write their structural formulae.
(ii) Name the type of isomerism involved.
(iii) Give the IUPAC name of 'A' and 'B'.
3)
Arrange the following complex in the increasing order of conductivity of their solution :
\([Co(NH_3)_3Cl_3],\ [Co(NH_3)_4Cl_2]\ Cl,\ [Co(NH_3)_6]\ Cl_3,\ [Cr(NH_3)_5Cl]\ Cl_2.\)

\(\)
4)
A complex of the type [M(AA)₂X₂]ⁿ⁺ is known to be optically active. What does this indicate about the structure of the complex ? Give one example of such complex.

CBSE 12th Standard Chemistry Subject Coordination Compounds Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Arrange following complex ions in increasing order of crystal field splitting energy \((\triangle_0)\) :
\([Cr(Cl)_6]^{3-}, [Cr(CN)_6]^{3-}, [Cr(NH_3)_6]^{3+}.\)

\(\)
2)
Why do compounds having similar geometry have different magnetic moment ?
3)
\(CuSO_4.5\ H_2O\) is blue in colour while \(CuSO_4\) is Colourless. Why ?
4)
Write the name, state of hybridization, shape and magnetic behaviour of the following complexes :
[CoCl₄]²^-,[Ni(CN)₄]^2-,[Cr(H₂O)₂(C₂O₄)₂]^-
(At. nos. : Co = 27, Ni = 28, Cr = 24)

CBSE 12th Standard Chemistry Subject The p-Block Elements Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
In the ring test of NO₃^- ion, Fe²⁺ ion reduces nitrate ion to nitric oxide, which combines with Fe²⁺(aq) ion to form brown complex. Write the reactions involved in the formation of brown ring.
2)
Explain why the acidity oxoacids of chlorine increases in the order given below:
HCIO < HCIO₂ < HCIO₃ 4
3)
P4O6 reacts with water according to equation,
P₄O₆ + 6H₂O \(\rightarrow\) 4H₃PO₃ . Calculate the volume of 0.1M NaOH solution required to neutralise the acid formed by dissolving 1.1g of P₄O₆ in H₂O.
4)
White phosphorus reacts with chlorine and the product hydrolyses in the presence of water. Calculate the mass of HCl obtained by the hydrolysis of the product formed by the reaction of 62g of white phosphorus with chlorine in the presence of water.
5)
Name three oxoacids of nitrogen. Write the disproportionation reaction of that oxoacid of nitrogen in which nitrogen is in +3 oxidation state.

CBSE 12th Standard Chemistry Subject The p-Block Elements Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
State reasons for each of the following:
(i) All the P-Cl bonds in PCl₅ molecule are not equivalent.
(ii) Sulphur has greater tendency for catenation than oxygen.
2)
Assign a reason for each of the following statements:
(i) More metal fluorides are ionic in nature than metal chlorides.
(ii) SCI₆ is not known but SF₆ is known.
3)
Explain why the stability of oxoacids of chlorine increases in the order given below:
HCIO< HCIO₂ < HCIO₃ < HCIO₄
4)
Write a balanced chemical equation for the reaction showing catalytic oxidation of NH₃ by atmospheric oxygen.
5)
Write the structure of pyrophosphoric acid.

CBSE 12th Standard Chemistry Subject General Principles and Processes of Isolation of Elements Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Which method is used for refining Zr and Ti? Explain with equation.
2)
Why is an external emf of more than 2.2 V required for the extraction of Cl₂ from brine?
3)
At temperature above 1073 K coke can used to reduce FeO to Fe.How can you justify this reduction with Ellingham diagram?
4)
Wrought iron is the purest form of iron.Write a reaction used for the preparation of wrought iron from cast iron.How can impurities of sulphur,silicon and phosphorus be removed from cast iron?
5)
How is copper extracted from low grade copper ores?

CBSE 12th Standard Chemistry Subject General Principles and Processes of Isolation of Elements Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Which method is used for refining Zr and Ti? Explain with equation.
2)
What should be the consideration during extraction of metals by electrochemical method?
3)
What is the role of flux in metallurgical processes?
4)
How are metals used as semiconductors refined?What is the principle of the method used?
5)
How is copper extracted from a low grade ore of it?

CBSE 12th Standard Chemistry Subject Surface Chemistry Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
How does it become possible to cause artifical rain by spraying silver iodide on the clouds?
2)
Gelatin which is a peptide is added in ice-creams. What can be its role?
3)
Why do we added alum to purify water?
4)
What happens when electric field is applied to colloidal solution?
5)
What causes brownian motion in colloidal dispersion?

CBSE 12th Standard Chemistry Subject Surface Chemistry Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
What are lyophilic and lyophobic colloids? Give one example of each type. Which one of these two types of sols is easily coagulated and why?
2)
Explain the following terms giving a suitable example for each:
(i) Aerosol
(ii) Emulsion
(iii) Micelle
3)
Define each of the following terms
(i) Micelles
(ii) Peptization
(iii) Desorption.
4)
Explain the following observations:
(a) A lyophilic colloid is more stable than lyophobic colloid.
(b) Coagulation takes place when sodium chloride solution is added to a colloidal solution of ferric hydroxide.
(c) The sky appears blue in color.
5)
Define the following and give an example of each
(a) Coagulation
(b) Tyndall effect.

CBSE 12th Standard Chemistry Subject Chemical Kinetics Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
The reaction between H₂ (g) and O₂ (g) is highly feasible yet allowing the gases to stand at room temperature in the same does not lead to the formation of water. Explain
2)
Why does the rate of a reaction increase with rise in temperature ?
3)
Why is the probability of reaction with molecularity higher than three very rare?
4)
Why does the rate of any reaction generally decreases during the course of the reaction ?
5)
Thermodynamic feasibility of the reaction alone cannot decide the rate of the reaction. Explain with the help of the one example .

CBSE 12th Standard Chemistry Subject Chemical Kinetics Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Write the rate equation for the reaction 2 A + B \(\longrightarrow\) C if the order of the reaction is zero.
2)
How can you determine the rate law of the following reaction ?
2 NO (g) + O₂ (g) \(\longrightarrow\) 2 NO₂ (g)
3)
For which type of reactions, order and molecularity have the same value ?
4)
In a reaction, if the concentration of reaction A is tripled, the rate of reaction becomes twenty seven times. What is the order of the reaction ?
5)
Derive an expression to calculate time required for completion of zero reaction.

CBSE 12th Standard Chemistry Subject Electrochemistry Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Consider the cell :Cu | Cu²⁺ || Cl^- | Cl₂ , Pt
Write the reactions that occur at anode and cathode.
2)
Write the Nernst equation for the cell reaction in the Daniel cell. How will the E_cell be affected when concentration of Zn²⁺ ions is increased ?
3)
What advantage do the fuel cells have over primary and secondary batteries ?
4)
Write the cell reaction of a lead storage battery when it is discharged. How does the density of the electrolyte change when the battery is discharged?
5)
Why on dilution the \({ \wedge }_{ m }\) of CH₃COOH increases drastically, while that of CH₃COONa increases gradually?

CBSE 12th Standard Chemistry Subject Electrochemistry Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Can absolute value of electrode potential of an electrode be measured ?
2)
Can \({ E }_{ cell }^{ 0 }\) and \({ \Delta }_{ r }{ G }^{ 0 }\) for cell reaction ever be equal to zero ?
3)
Aqueous copper sulphate solution and aqueous silver nitrate solution are electrolysed by 1 ampere current for 10 minutes in separate electrolytic cells. Will the mass of copper and silver deposited on the cathode be same or different ? Explain your answer.
4)
Depict the galvanic cell in which the cell reaction is Cu(s) + 2Ag⁺ (aq) \(\longrightarrow\) 2Ag(s) + Cu²⁺ (aq)
5)
Value of standard electrode potential for the oxidation of Cl^- ions is more positive than that of water, even then in the electrolysis of aqueous sodium chloride, why is Cl^- oxidised at anode instead of water ?

CBSE 12th Standard Chemistry Subject Solution Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
(a) Define Azeotropes and explain broefly minimum boiling azeotrope by taking suitable example.
(b) The vapour pressures of pure liquids A and B are 450 mm 700 mm of Hg respectively at 350 K. Calculate the composition of the liquid mixture if total vapour pressure is 600 mm of Hg. Also find the composition of the mixture in the vapour phase.
2)
Explain the solubility rule 'like dissolves like' in terms of intermolecular forces that exist in solutions.
3)
Why is the vapour pressure of a solution of glucose in water lower than that of water?
4)
Explain, why on addition of mole of NaCI to 1L of water, the boiling point of water increases, while addition of 1mole of methyl alcohol to 1L of water decreases its boiling point?
5)
When kept in water, raisin swells in size. Name and explain the phenomenon involved with the help of a diagram. Give three applications of the phenomenon.

CBSE 12th Standard Chemistry Subject Solution Ncert Exemplar 2 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Explain why on addition of 0 mol of NaCI to 1 litre of water, the boiling point of water increases, while addition of 1 mol of methyl alcohol to one litre of water decreases its boiling point.
2)
Concentration terms such as mass percentage, ppm, mole fraction and molality are independent of temperature, however molarity is a function of temperature. Explain.
3)
What is the significance of Henry's Law constant K_H?
4)
Why are aquatic species more comfortable in cold water in comparison to warm water ?
5)
(a) Explain the following phenomena with the help of Henry's law.
(i) Painful condition known as bends.
(ii) Feeling of weakness and discomfort in breathing at high altitude.
(iii) Why soda water bottle kept at room temperature fizzes on opening ?

CBSE 12th Standard Chemistry Subject General Principles and Processes of Isolation of Elements Ncert Exemplar 1 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Name the method used for refining of
(i)copper metal
(ii) nickel method.
2)
Mention two important substances present in the 'anode mud' obtained in the electrorefining of copper.
3)
What is the principle of zone refinijng?
4)
Give an example of zone refining of metals.
5)
What are the main components of invar?

CBSE 12th Standard Chemistry Subject General Principles and Processes of Isolation of Elements Ncert Exemplar 1 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
How is copper extracted from a low grade ore of it?
2)
Name a sulphide ore of copper
3)
(a) Why is it that only sulphide ores are concentrated by froth floatation process?
(b) Which of the following ores can be concentrated by froth floatation method and Why?
4)
What is the role of a stabilizer in the froth floatation process?
5)
what is the composition of copper matte?

CBSE 12th Standard Chemistry Subject Electrochemistry Ncert Exemplar 1 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Why is it not possible to measure the single electrode potential ?
2)
Given that the standard electrode potentials \(\left( { E }^{ 0 } \right) \) of metals are :
\({ K }^{ + }/K=-2.93V,{ Ag }^{ + }/Ag=0.80V,\) \({ Cu }^{ 2+ }/Cu=0.34V,{ Mg }^{ 2+ }/Mg=-2.37V\) \({ Cr }^{ 3+ }/Cr=-0.74V,{ Fe }^{ 2+ }/Fe=-0.44V\)
Arrange these metals in an increasing order of their reducing power.
3)
Define electrochemical series . or two applications of electrochemical series.
4)
Why does zinc react with dilute sulphuric acid but copper does not?
5)
Write the name of a cell used in small watches.

CBSE 12th Standard Chemistry Subject Electrochemistry Ncert Exemplar 1 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
What is meant by Faraday constant?
2)
How many faradays of electric charge is required to liberate 5600 cm³ of oxygen at STP ?
3)
How do metallic and ionic substances differ in conducting electricity ?
4)
Express the relation among conductivity of the solution in the cell, the cell constant and resistance of solution in the cell.

CBSE 12th Standard Chemistry Subject Solution Ncert Exemplar 1 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
What is the effect of temperature on the solubility of sodium sulphate decahyrate ?
2)
Define transition temperature in solubility of a solid in a liquid.
3)
State the formula relating pressure of a gas with its mole fraction in a liquid solution in contact with it.
4)
What type of liquids form ideal solutions ?
5)
What is the boiling point of an azeotrope of non - ideal solution showing positive deviations as compared to the boiling points of its components ?

CBSE 12th Standard Chemistry Subject Solution Ncert Exemplar 1 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Why does water from the soil rise to the top of a tall tree ?
2)
What happens when blood cells are placed in pure water ?
3)
Define molal elevation constant or ebullioscopic constant.
4)
Define molal depression constant/cryoscopic constant.
5)
Give one most important application of the phenomenon of depression in freezing point in everyday life.

CBSE 12th Standard Chemistry Subject The Solid State Ncert Exemplar 1 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
What is the difference between 13-15 and 12-16 compounds?
2)
What is F-centre?
3)
Name the type of point defect that occurs in a crystal of zinc sulphide.
4)
Which point defect in crystals of a solid does not change the density of the solid?
5)
What happens when a ferromagnetic or anti-ferromagnetic or a ferrimagnetic solid is heated?

CBSE 12th Standard Chemistry Subject The Solid State Ncert Exemplar 1 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
How can you convert NaCl structure into CsCl structure and vice versa?
2)
MgO has the structure of NaCl and TlCl has the structure of CsCl. What are the coordination numbers of the ions in MgO and TlCl?
3)
Arrange the following according to their packing fractions:
Simple cubic, face-centred cubic, body-centred cubic.
4)
A compound AB₂ possesses the CaF₂ type crystal structure. Write the coordination numbers of A²⁺ and B^- ions in its crystals.
5)
Defain coordination number of a metal ion in an ionic crystal.

CBSE 12th Standard Chemistry Subject Surface Chemistry Ncert Exemplar 1 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
What is the main cause of charge on a colloidal solution?
2)
Name the type of potential difference produced between the fixed charge layer and diffsed layer having opposite charges around the colloidal particle.
3)
Define electrophoresis.
4)
Which of the following is most effective electrolyte in the coagulation of Fe₂O₃.H₂O/Fe³⁺ sol?

KCI, AICI₃, MgCl₂, K₄[Fe(CN)₆]
5)
Give one example each of 'oil in water' and water in oil' emulsion.

CBSE 12th Standard Chemistry Subject Surface Chemistry Ncert Exemplar 1 Mark Questions 2021 - by Archana Singh - Deoghar - May 25, 2021 - View & Read

1)
Why is chemisorption irreversible?
2)
What is meant by chemical adsorption?
3)
Which has a higher enthalpy of adsorption, physisorption or chemisorption?
4)
Give the expression of Freundlich isotherms.
5)
How does an increase in temperature affect both physical as well as chemical adsorption?

CBSE 12th Standard Chemistry Subject Chemistry in Everyday Life Ncert Exemplar Match the following Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Antihistamines
2)
Antacids
3)
Tranquillisers
4)
Antibiotics
5)
Disinfectants

CBSE 12th Standard Chemistry Subject Chemistry in Everyday Life Ncert Exemplar Match the following Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Ranitidine
2)
Furacine
3)
Phenelzine
4)
Chloramphenicol
5)
Soap chips

CBSE 12th Standard Chemistry Subject Surface Chemistry Ncert Exemplar Match the following Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Sulphur vapours passed through cold water
2)
Soap mixed with water above critical micelle concentration
3)
Solved molecules pass through semipermeable member towards solvent side
4)
Movement of charged colloidal particles under the influence of applied electric potential towards oppositely charged electrodes
5)
Solvent molecules pass through semipermeable menbers towards solution side

CBSE 12th Standard Chemistry Subject Surface Chemistry Ncert Exemplar Match the following Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Peptisation
2)
Emulsification
3)
Butter
4)
Milk
5)
Paints

CBSE 12th Standard Chemistry Subject Electrochemistry Ncert Exemplar Match the following Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
E_cell
2)
G^*
3)
k
4)
Au
5)
Li⁺

CBSE 12th Standard Chemistry Subject Electrochemistry Ncert Exemplar Match the following Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Ni-Cd cell
2)
Fuel cell
3)
Mercury cell
4)
Li
5)
Au³⁺

CBSE 12th Standard Chemistry Subject Chemistry in Everyday Life Ncert Exemplar Fill Ups Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which class of drugs is used in sleeping pills?
2)
Which site of an enzyme is called allosteric site?
3)
________ is the branch of chemistry which deals with the treatment of diseases using chemicals.
4)
Give one example of a
(i) bactericidal antibiotic
(ii) bacteriostatic antibiotic.
5)
Where are the receptors located?

CBSE 12th Standard Chemistry Subject Biomolecules Ncert Exemplar Fill Ups Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which one of the following is a disaccharide : strach, Maltose, Fructose, Glucose ?
2)
What are tetrasaccharides ? Give an example.
3)
What are polysaccharides ? Give one example.
4)
Name one reducing and one-non reducing disaccharide .
5)
What is mutarotation?

CBSE 12th Standard Chemistry Subject Biomolecules Ncert Exemplar Fill Ups Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Vitamin 'C' is a vitamin found in fruits and vegitables. It cannot be stored in our body. why ?
2)
What purine and pyrimidine base are present in DNA and RNA ?
3)
Name the base which is present in nucleotide of RNA only.
4)
What are type of linkage holds together the monomers of DNA?
5)
Name the three nucleic acids used in protein synthesis.

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers Ncert Exemplar Fill Ups Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
What is 'Power alcohol'?
2)
A little water is there on the inner surface of a conical flask. Can this water be removed by shaking with ether? Answer with reason.
3)
Why are higher ethers insoluble in water?
4)
Identify the allylic alcohols in the following examples.
5)
Write the IUPAC name of the compound given below:

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers Ncert Exemplar Fill Ups Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Suggest a reagent for the following conversion.
2)
Anhydrous CaCl₂ is not recommended as a drying agent for alcohols and amines.
3)
What is the order of reactivity of HCl, HBr and Hl with alcohols?
4)
The relative ease of dehydration of alcohols is : tertiary > secondary > primary
5)
Name one reagent which is used for the distinction of primary,secondary and tertiary alcohols

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes Ncert Exemplar Fill Ups Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Racemic mixture is optically inactive. Give reason.
2)
Iodoform has antiseptic properties. Give one reason to support it.
3)
Out of o-and p-dibromobenzene which one has higher melting point and why?
4)
Write the structures and names of the compounds formed when compound 'A' with molecular formula, C₇H₈is treated with Cl₂ in the presence of FeCl_3.
5)
Identify the products A and B formed in the following reaction:CH₃-CH₂-CH = CH-CH₃+HCl \(\longrightarrow\) A+B

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes Ncert Exemplar Fill Ups Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Explain why thionyl chloride method is preferred for preparing alkyl chlorides from alcols?
2)
How will you obtain 1-bropropane from propane ?
3)
How will you bring about the conversion : methyl bromide to methyl iodide ?
4)
Organic halogon compounds used in industry as solvents are chlorides rather than bromides and iodides. Explain
5)
Which is a better nucleophile, a bromide ion or an idodide ion ?

CBSE 12th Standard Chemistry Subject Coordination Compounds Ncert Exemplar Fill Ups Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
What happens when potassium ferrocyanide solution is added to a ferric salt solution ?
2)
Name the different types of organometallic compounds.
3)
In the formula \(Fe(\eta ^5-C_5H_5)\) what does the prefix \(\eta ^5\) denote ?
4)
What is the oxidation state of Ni in Ni(CO)₄ ?
5)
How is tetrabutyl tin prepared ?

CBSE 12th Standard Chemistry Subject Coordination Compounds Ncert Exemplar Fill Ups Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Give one example of a bidentate ligand.
2)
What is the name of the bidentate ligand 'dmg' ?
3)
Give an example of a hexadentate ligand.
4)
Give one example of each :
(a) Neutral ligand of carbon
(b) Positive ligand of nitrogen.

CBSE 12th Standard Chemistry Subject The d- and f- Block Elements Ncert Exemplar Fill Ups Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Among landthanoids, Ln(III) compounds are predominant. however, occasionally in solutions or in solid compounds, +2 and +4 ions are also obtained. Give reason.
2)
There is hardly any increase in atomic size with increasing atomic numbers in a series of transition metals. Give reason.
3)
Complete and balance the following chemical equation Cr₂O₇^2-+I^-+H⁺\(\longrightarrow \) _________________.
4)
What is meant by 'lanthanoid contraction'?
5)
Write the outer electronic configuration of Cr atom (Z=24).

CBSE 12th Standard Chemistry Subject The d- and f- Block Elements Ncert Exemplar Fill Ups Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
What is meant by lanthanoid contraction ?
2)
Why is the separation of lanthanoide elements difficult ?
3)
Explain why lanthanoids are paramagnetic in nature ?
4)
Give the general electronic configuration of Actinides.
5)
Write the electronic configuration of the element with atomic number 102.

CBSE 12th Standard Chemistry Subject The p-Block Elements Ncert Exemplar Fill Ups Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Give reasons for the least rectivity of nitrogen molecule.
2)
Which is least acidic ? SbH₃, Ph₃, NH₃,AsH₃
3)
Which is least basic ? SbH₃, PH₃, NH₃, ASH₃ ?
4)
Which is a stronger reducing agent, SbH₃ or BiH₃, and why?
5)
Which of the following is/are not known ? PCl₃, AsCl₃, SbCl₃, NCl₅, BiCl₅.

CBSE 12th Standard Chemistry Subject The p-Block Elements Ncert Exemplar Fill Ups Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Write two names of interhalogen compounds having sp³d² hybridization.
2)
Noble gases are monoatomic in nature. Explain.
3)
Why do boiling points of noble gases increase from helium to radon?
4)
Which compound led to the discovery of compounds of noble gases ?
5)
Complete the following : \(XeF_2+PF_5\rightarrow\)

CBSE 12th Standard Chemistry Subject Surface Chemistry Ncert Exemplar Fill Ups Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Give an example where physisorption changes to chemisorption with rise in temperature? Explain the reason for change.
2)
Why are some medicines more effective in the colloidal form?
3)
What happens when dialysis is prolonged?
4)
Why does the white precipitate of silver halide become coloured in the presence of dye eosin?
5)
What is the role of activated charcoal in gas mask used in coal mines?

CBSE 12th Standard Chemistry Subject Chemistry in Everyday Life Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Transparent soaps are made by dissolving the soap in
2)
Which of the following is an example of liquid dishwashing detergent?
3)
Polyethyleneglycols are used in the preparation of which type of detergents?
4)
Which class of the drugs is used as pain killer?
5)
Paracetamol reduces

CBSE 12th Standard Chemistry Subject Chemistry in Everyday Life Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
The most useful classification of drugs for medicinal chemists is ___________.
2)
Salvarsan is arsenic containing drug which was first used for the treatement of .............. .
3)
A narrow spectrum antibiotic is active against ........... .
4)
The compound that causes general anti-depressant action on the central nervous system belongs to the class of ............ .
5)
Equanil is ............ .

CBSE 12th Standard Chemistry Subject Polymers Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which of the following is not a semisynthetic polymer?
2)
The commercial name of polyacrylonitrile is .......
3)
Which of the following statements is not true about low density polythene?
4)
Which of the following polymers,need atleast one diene monomer for their preparation?
5)
Which of the following are characteristics of thermosetting polymers?

CBSE 12th Standard Chemistry Subject Polymers Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which of the following polymers have vinylic monomer units?
2)
is a polymer having monomer units _________.
3)
In which of the following polymers ethylene glycol is one of the monomer units?
4)
Which of the following polymer can be formed by using the following monomer unit?
5)
Which of the following polymer is biodegradable?

CBSE 12th Standard Chemistry Subject Biomolecules Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which of the following polymer is stored in the liver of animals ?
2)
Ribose and 2-deoxyribose can be differentiated by
3)
Which statement is incorrect about peptide bond ?
4)
One molecule of sucrose on hydrolysis gives ___________.
5)
Tertiary structure of protein is stabilised by

CBSE 12th Standard Chemistry Subject Biomolecules Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
DNA and RNA contain four bases each. which of the following bases is not present in RNA ?
2)
Which of the following B group vitamins can be stored in our body ?
3)
Which of the following bases is not present in DNA ?
4)
Which of the following reactions of glucose can be explained only its cyclic structure ?
5)
Carbohydrates are classified on the basis of their behaviour on hydrolysis and also as reducing or non-reducing sugar. Surcose is a ......... .

CBSE 12th Standard Chemistry Subject Amines Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
The correct IUPAC name for CH₂=CHCH₂NHCH₃ is
2)
Benzylamine may be alkylated as shown in the following equation:

C₆H₅CH₂NH₂+R-X \(\longrightarrow \) C₆H₅CH₂NHR

Which of the following alkyl halides is best suited for this reaction through S_N 1 mechanism?
3)
In order to prepare a \({ 1 }^{ \circ }\) amine from an alkyl halide with simultaneous addition of one CH₂ group in the carbon chain, the reagent used as source of nitrogen is.................................. .
4)
The best reagent for converting 2-phenylpropanamide into 2-phenylpropanamine is........................... .
5)
The best reagent for converting, 2-phenylpropanamide into 1-phenylethanamine is.................................. .

CBSE 12th Standard Chemistry Subject Amines Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
The best reagent for converting, 2-phenylpropanamide into 1-phenylethanamine is.................................. .
2)
Methylamine reacts with NHO₂ to form...................................... .
3)
The gas evolved when methylamine reacts with nitrous acid is.......................... .
4)
Reduction of aromatic nitro compounds using Fe and HCI gives............................ .
5)
Which of the following is a 3° amine?

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Through which of the following reactions number of carbon atoms can be increased in the chain ?
2)
Benzophenone can be obtained by ______________ .
3)
Addition of water to butyne occurs in acidic medium and in the presence of Hg²⁺ ions as a catalyst. The product formed is
4)
Which of the following compounds is most reactive towards nucleophilic addition reactions?
5)
Cannizzaro's reaction is not given by ____________.

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
The correct order of increasing acidic strength is ________________.
2)
The reagent which does not react with both, acetone and benzaldehyde is
3)
Which of the following compounds will give butanone on oxidation with alkaline KMnO₄ solution?
4)
In Clemmensen reduction, carbonyl compound is treated with _____________ .
5)
Which of the following conversions can be carried out by Clemmensen reduction ?

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Monochlorinaton of toluene in sunlight followied by hydrolysis with aq.NaOH yields.
2)
How many alcohols with molecular formula C₄H₁₀O are chiral in nature?
3)
What is the correct order of reactivity of alcohols in the following reaction?
\(R-OH+HCI\overset { ZnCl_{ 2 } }{ \longrightarrow } R-Cl+{ H }_{ 2 }O\)
4)
Give IUPAC name of the compound given below.
5)
CH₃CH₂OH can be converted into CH₃CHO by

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
The reaction of toluene with chlorine in the presence of iron and in the absence of light yields ___________.
2)
Which of the following compounds will give racemic mixture on nucleophilic substitution by OH^- ion?
3)

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Toluene reacts with a halogen in the presence of iron (III) chloride giving ortho and para halo compounds. The reaction is
2)
Which reagent will you use for the following reaction?
CH₃CH₂CH₂CH₃ \(\longrightarrow\) CH₃CH₂CH₂CH₂Cl+CH₃CH₂CHClCH₃
3)
Which of the following is an example of vic-dihalide?
4)
Chlorobenzene is formed by reaction of chlorine with benzene in the presence of AlCl₃. Which of the following species attacks the benzene ring in this reaction?
5)
Ethylidene chloride is a/an ............

CBSE 12th Standard Chemistry Subject Coordination Compounds Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
When 0.1 mol CoCl₃ (NH₃)₅ is treated with excess of AgNO₃ , 0.2 mol of AgCl are obtained. The conductivity of solution will correspond to
2)
When 1 mol CrCl₃.6H₂O is treated with excess of AgNO₃, 3 mol of AgCl are obtained. The formula of the complex is
3)
The correct IUPAC name of [Pt(NH₃)₂Cl] is
4)
The stabilisation of coordination compounds due to chelation is called the chelate effect. Which of the following is the most stable complex species?
5)
Indicate the complex ion which shows geometrical isomerism.

CBSE 12th Standard Chemistry Subject Coordination Compounds Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Atomic number of Mn, Fe and Co are 25,26 and 27 respectively. Which of the following inner orbital octahedral complex ions are diamagnetic ?
2)
Atomic number of Mn, Fe, Co and Ni are 25, 26, 27 and 28 respectively. Which of the following outer orbital octahedral complexes have same number of unpaired electrons ?
3)
Which of the following options are correct for \([Fe(CN)_6]^{3-}\) complex ?
4)
An aqueous pink solution of cobalt(II) chloride changes to deep blue on addition of excess of HCl. This is because............... .
5)
Which of the following complexes are homoleptic ?

CBSE 12th Standard Chemistry Subject The d- and f- Block Elements Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which of the following lanthanoids show +2 oxidation state besides the characteristic oxidation state +3 of lanthanoids?
2)
Which of the following ions show higher spin only magnetic moment value ?
3)
Transition elements form binary compounds with halogens. Which of the following elements will form MF₃ type compounds ?
4)
Which of the following will not act as oxidising agents ?
5)
Although +3 is the characteristic oxidation state for lanthanoids but cerium also shows +4 oxidation state because ......... .

CBSE 12th Standard Chemistry Subject The d- and f- Block Elements Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Electronic configuration of a transition element X in +3 oxidation state is [Ar] 3d⁵. What is its atomic number ?
2)
The electronic configuration of Cu (II) is 3d⁹ whereas that of Cu (I) is 3d¹⁰ . Which of the following is correct ?
3)
Metallic radii of some transition elements are given below. Which of these elements will have hig

Element Fe Co Ni Cu

Metallic 126 125 125 128
4)
Generally transition elements form coloured salts due to the presence of unpaired electrons. Which of the following compounds will be coloured in solid state ?
5)
On addition of small amount of KMnO₄ to concentrated H₂SO₄, a green oily compound is obtained which is highly explosive in nature, Identify the compound from the following.

CBSE 12th Standard Chemistry Subject The p-Block Elements Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which of the following acids forms three series of salts?
2)
Strong reducing behaviour of H₃PO₂ is due to
3)
On heating, lead nitrate forms oxides of nitrogen and lead. The oxides formed are.......
4)
Which of the following elements does not show allotropy?
5)
Maximum covalency of nitrogen is.....

CBSE 12th Standard Chemistry Subject The p-Block Elements Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
On addition of conc.H₂SO₄ to a chloride salt, colourless fumes are evolved but in case of iodide salt, violet fumes comes out. This is because
2)
In quantitative analysis when H₂S is passed through an aqueous solution of salt acidified with dil . HCl, a black precipitate is obtained. On boiling the precipitate with dil . HNO₃it forms a solution of blue colour. Addition of excess of aqueous solution of ammonia to this solution gives.......
3)
In a cyclo tri metaphosphoric acid molecule, how many single and double bonds are present?
4)
Which of the following elements can be involved in p\(\pi\)-d\(\pi\) bonding?
5)
Which o the following pairs of ions are isoelectronic and isostructural?

CBSE 12th Standard Chemistry Subject General Principles and Processes of Isolation of Elements Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
The main reactions occurring in blast furnace during extraction of iron from haematite are______________.
2)
Which of the following statements are correct?
3)
In the extraction of chlorine from brine _____________________.
4)
When copper ore is mixed with silica in a reverberatory furnace, copper matte is produced. The copper matte contains
5)
Electrolytic refining is used to purify which of the following metals?

CBSE 12th Standard Chemistry Subject General Principles and Processes of Isolation of Elements Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
In the extraction of chlorine by electrolysis of brine.......
2)
When copper ore is mixed with silica,in a reverberatory furnace,copper matte is produced.The copper matte contains.....
3)
Which of the following reactions is an exam[le of autoreduction?
4)
A number of elements are available in earth,s crust but most abundant elements are __________________.
5)
Zone refining is based on the principle that.....

CBSE 12th Standard Chemistry Subject Surface Chemistry Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
H₂ gas is adsorbed on activated charcoal to a very little extent in comparion to easily liquefiable gases due to................................ .
2)
An emulsion cannot be broken by.........................and......................... .
3)
Which of the following colloids cannot be coagulated easily?
4)
Which phenomenon occurs when an electric field is applied to a colloidal solution and electrophoresis is prevented?
5)
Which of the following phenomenon occurs when a chalk stick is dipped in ink?

CBSE 12th Standard Chemistry Subject Surface Chemistry Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Given below, catalyst and corresponding process/reaction are matched. The mismatch is
2)
The volume of a colloidal particle, V_c as compared to the volume of a solute particle in a true solution, V_s could be
3)
The dispersed phase and dispersion medium in soap lather are respectively
4)
The dispersed phase and dispersion medium of fog respectively are
5)
Which one of the following is correctly matched ?

CBSE 12th Standard Chemistry Subject Electrochemistry Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
\({ \wedge }_{ m }^{ 0 } \ { H }_{ 2 }O\) is equal to __________________.
2)
What will happen during the electrolysis of aqueous solution of CuSO₄ by using platinum electrodes?
3)
Conductivity k, is equal to __________________.
4)
Molar conductivity of ionic solution depends on -------
5)
For the given cell, \(Mg|{ Mg }^{ 2+ }||{ Cu }^{ 2+ }|Cu\)

CBSE 12th Standard Chemistry Subject Electrochemistry Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which cell will measure standard electrode potential of copper electrode?
2)
Which of the following statement is correct ?
3)
The difference between the electrode potentials of two electrodes when no current is drawn through the cell is called -------------
4)
Which of the following statement is not correct about an inert electrode in a cell ?
5)
An electrochemical cell can behave like an electrolytic cell when --------

CBSE 12th Standard Chemistry Subject Solution Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which of the following units is useful in relating concentration of solution with its vapour pressure ?
2)
On dissolving sugar in water at room temperature, solution feels cool to touch. Under which of the following cases dissolution of sugar will be most rapid ?
3)
At equilibrium the rate of dissolution of a solid solute in a volatile liquid solvent is ................... .
4)
A breaker contains a solution of substance 'A'. Precipitation of substance 'A' takes place when small amount of 'A' is added to the solution. The solution is ................ .
5)
Maximum amount of a solid solute that can be dissolved in a specified amount of a given liquid solvent does not depend upon __________________.

CBSE 12th Standard Chemistry Subject Solution Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which following factor (s) affect the solubility of a gaseous solute in the fixed volume of liquid solvent ?
(i) nature of solute
(ii) temperature
(iii) pressure
2)
4 L of 0.02 M aqueous solution of NaCI was diluted by adding 1L of water. The molarity of the resultant solution is............
3)
Which of the following aqueous solutions should have the highest boiling point?
4)
What happens to freezing point of benzene when naphthalene is added?
5)
The order of boiling points of four equimolar aqueous solutions is C < B < A < D. The correct order of their freezing points is

CBSE 12th Standard Chemistry Subject The Solid State Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which of the following oxides shows electrical properties like metals?
2)
In which of the following structures coordination number for cations and anions in the packed structure will be same?
3)
A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field because........................ .
4)
Which of the following statements are true about metals?

CBSE 12th Standard Chemistry Subject The Solid State Ncert Exemplar MCQ Questions 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which of the following oxides shows electrical properties like metals?
2)
In which pair most efficient packing packing is present?
3)
What is the coordination number in a square close packed structure in two dimensions?
4)
A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field because........................ .
5)
Which of the following statements are true about metals?

CBSE 12th Standard Chemistry Subject Ncert Exemplar 5 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
On heating, lead (II) nitrate gives a brown gas 'A'. The gas 'A' on cooling changes to colourless solid 'B'. Solid 'B' on heating with NO changes to a blue solid 'C'. Identiy 'A', 'B' and 'C' and also write reactions involved and draw the structures of 'B' and 'C'.
2)
On heating compound(A) gives a gas (B) which is a constituent of air. This gas when treated with 3 mol of hydrogen (H₂) in the presence of a catalyst gives another gas (C) which is basic in nature. Gas C on further oxidation in moist condition gives a compound (D) which is a part of acid rain. Identify compounds (A) to (D) and also give necessary equations of all the steps involved.
3)
An amorphous solid A burns in air to form a gas B which turns lime water milky. The gas is also produced as a byproduct during roasting of sulphide ore. This gas decolourises acidified aqueous KMnO₄ solution and reduces Fe ³⁺ to Fe²⁺. Identify the solid 'A' and the gas 'B ' and write the reactions involved.
4)
(a) Out of Ag₂SO₄, CuF₂, MgF₂ and CuCI, which compound will be coloured and why?
(b) Explain :
(i) \({ CrO }_{ 4 }^{ 2- }\) is a strong oxidizing agent while \({ MnO }_{ 4 }^{ 2- }\) is not.
(ii) Zr and Hf have identical sizes.
(iii) The lowest oxidation state of manganese is basic while the highest is acidic.
(iv) Mn (II) shows maximum paramagnetic character amongst the divalent ions of the first transition series.
5)
Using crystal field theory, draw energy level diagram, write electronic configuration of the central metal atom/ion and determine the magnetic moment value in the following :
(i) \([CoF_6]^{3-}, [Co(H_2O)_6]^{2+},[Co(CN)_6]^{3-}\)
(ii) \([FeF_6]^{3-}, \ [Fe(H_2O)_6]^{2+}, [Fe(CN)_6]^{4-}\).

CBSE 12th Standard Chemistry Subject Ncert Exemplar 5 Mark Questions 2021 Part - I - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
(a) what is meant by rate of a reaction.
(b) In a pseudo first order hydrolysis of ester in water, the following results are obtained:

t in seconds 0 30 60 90

[Ester] M 0.55 0.31 0.17 0.085

(i) Calculate the average rate of reaction between the time interval 30 to 60 seconds.
(ii) Calculate the pseudo first order rate constant for the hydrolysis of ester.
2)
Write down the reactions taking place in different zones in the blast furnace during the extraction of iron.
3)
On heating, lead (II) nitrate gives a brown gas 'A'. The gas 'A' on cooling changes to colourless solid 'B'. Solid 'B' on heating with NO changes to a blue solid 'C'. Identiy 'A', 'B' and 'C' and also write reactions involved and draw the structures of 'B' and 'C'.
4)
On heating compound(A) gives a gas (B) which is a constituent of air. This gas when treated with 3 mol of hydrogen (H₂) in the presence of a catalyst gives another gas (C) which is basic in nature. Gas C on further oxidation in moist condition gives a compound (D) which is a part of acid rain. Identify compounds (A) to (D) and also give necessary equations of all the steps involved.
5)
Using crystal field theory, draw energy level diagram, write electronic configuration of the central metal atom/ion and determine the magnetic moment value in the following :
(i) \([CoF_6]^{3-}, [Co(H_2O)_6]^{2+},[Co(CN)_6]^{3-}\)
(ii) \([FeF_6]^{3-}, \ [Fe(H_2O)_6]^{2+}, [Fe(CN)_6]^{4-}\).

CBSE 12th Standard Chemistry Subject Ncert Exemplar 5 Mark Questions 2021 Part - II - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
(a) what is meant by rate of a reaction.
(b) In a pseudo first order hydrolysis of ester in water, the following results are obtained:

t in seconds 0 30 60 90

[Ester] M 0.55 0.31 0.17 0.085

(i) Calculate the average rate of reaction between the time interval 30 to 60 seconds.
(ii) Calculate the pseudo first order rate constant for the hydrolysis of ester.
2)
What are the applications of adsorption in chemical analysis?
3)
Write down the reactions taking place in different zones in the blast furnace during the extraction of iron.
4)
An amorphous solid 'A' burns in air to form a gas 'B' which turns lime water milky. The gas is also produced as a by-product during roasting of sulphide ore. This gas decolourises acidified aqueous KMnO₄solution and reduces Fe³⁺ to Fe²⁺Identify the solid "A" and the gas "B" and write the reactions involved.
5)
On heating, lead (II) nitrate gives a brown gas 'A'. The gas 'A' on cooling changes to colourless solid 'B'. Solid 'B' on heating with NO changes to a blue solid 'C'. Identiy 'A', 'B' and 'C' and also write reactions involved and draw the structures of 'B' and 'C'.

CBSE 12th Standard Chemistry Subject Ncert Exemplar 2 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Inspite of long range order in the arrangement of particles why are the crystals usually not perfect?
2)
Why are aquatic species more comfortable in cold water in comparison to warm water ?
3)
Why is the vapour pressure of a solution of glucose in water lower than that of water?
4)
Depict the galvanic cell in which the cell reaction is Cu(s) + 2Ag⁺ (aq) \(\longrightarrow\) 2Ag(s) + Cu²⁺ (aq)
5)
What advantage do the fuel cells have over primary and secondary batteries ?

CBSE 12th Standard Chemistry Subject Ncert Exemplar 2 Mark Questions 2021 Part - II - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Why does white ZnO (s) become yellow upon heating?
2)
Why is the vapour pressure of an aqueous solution of glucose lower than that of water?
3)
Can \({ E }_{ cell }^{ 0 }\) and \({ \Delta }_{ r }{ G }^{ 0 }\) for cell reaction ever be equal to zero ?
4)
Consider the cell :Cu | Cu²⁺ || Cl^- | Cl₂ , Pt
Write the reactions that occur at anode and cathode.
5)
For a general reaction A \(\longrightarrow\) B, plot of concentration of A vs time is given in Fig. Answer the following questions on the basis of this graph.
(i) What is the order of the reaction ?
(ii) What is the slope of the curve ?
(iii) What are the units of rate constant

CBSE 12th Standard Chemistry Subject Ncert Exemplar 2 Mark Questions 2021 Part - I - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Why does table salt, NaCl, sometimes appear yellow in colour?
2)
What is the significance of Henry's Law constant K_H?
3)
What is ''semi-permeable'' membrane?
4)
Explain, why on addition of mole of NaCI to 1L of water, the boiling point of water increases, while addition of 1mole of methyl alcohol to 1L of water decreases its boiling point?
5)
Aqueous copper sulphate solution and aqueous silver nitrate solution are electrolysed by 1 ampere current for 10 minutes in separate electrolytic cells. Will the mass of copper and silver deposited on the cathode be same or different ? Explain your answer.

CBSE 12th Standard Chemistry Subject Ncert Exemplar Fill Ups Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
What is meant by 'shape-selective catalysis' of reactions?
2)
Give reasons for the least rectivity of nitrogen molecule.
3)
Write one reducing property of nitrous acid. Also give equation.
4)
Account for the following : PCl₅is more covalent than PCl₃.
5)
Which is the most common oxidation contraction ?

CBSE 12th Standard Chemistry Subject Ncert Exemplar Fill Ups Questions 2021 Part - II - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
What causes Brownian movement in a colloidal solution?
2)
Out of H₂O and H₂S, which one has higher bond angle and why?
3)
Which of the following is/are not known ? PCl₃, AsCl₃, SbCl₃, NCl₅, BiCl₅.
4)
Why is white phosphorus kept under water ?
5)
Write the structure of a chalcogenide dianion.

CBSE 12th Standard Chemistry Subject Ncert Exemplar Fill Ups Questions 2021 Part - I - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
What causes Brownian movement in a colloidal solution?
2)
Which is a stronger reducing agent, SbH₃ or BiH₃, and why?
3)
Write balanced chemical equation for the reaction : phosphorus is treated with concentrated nitric acid.
4)
Write one chemical reaction to show that conc. H₂SO₄can act as an oxidising agent.
5)
Why does a transition series contain 10 elements ?

CBSE 12th Standard Chemistry Subject Ncert Exemplar Match the Following Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
X=At the corner and face centres , Y=In all Terahedral voids
2)
Ferrites
3)
E_cell
4)
Silver
5)
Average rate

CBSE 12th Standard Chemistry Subject Ncert Exemplar Match the Following Questions 2021 Part - II - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
CuSO₄.5 H₂O
2)
Zns
3)
Ionic solids
4)
Lead storage battery
5)
Concentration of copper sulphate solution is doubled

CBSE 12th Standard Chemistry Subject Ncert Exemplar Match the Following Questions 2021 Part - I - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
E_cell
2)
Q
3)
Au³⁺
4)
Soap mixed with water below critical micelle concentration
5)
Movement of charged colloidal particles under the influence of applied electric potential towards oppositely charged electrodes

CBSE 12th Standard Chemistry Subject Ncert Exemplar 1 Mark Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
What are \(\triangle G,\ \triangle H\ and\ \triangle S\) for adsorption of gas on solid adsorbent?
2)
Write two difference between sols and emulsions.
3)
Why must vitamin C be supplied regularly in diet?
4)
In a crystal of zinc sulphide, zinc occupies tetrahedral voids. What is the coordination number of zinc?
5)
What other element may be added to silicon to make electrons available for conduction of an electric current?

CBSE 12th Standard Chemistry Subject Ncert Exemplar 1 Mark Questions 2021 Part - II - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
What do you mean by specific surface area of an adsorbent?
2)
What is photovoltaic cell?
3)
Why is potassium chloride sometimes violet instead of pure white?
4)
What is the relation between normality and molarity of a given solution of H₂SO₄ ?
5)
What happens when blood cells are placed in pure water ?

CBSE 12th Standard Chemistry Subject Ncert Exemplar 1 Mark Marks Questions 2021 Part - I - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
If both adsorption and absorption take place simultaneously, the precess is called..................... .
2)
Adsorption of a gas on the surface of solid is generally accompained by decrease in entropy. Still it is a spontaneous process. Explain.
3)
How can we remove moisture from glass apparatus?
4)
Draw the structure of CIF₃
5)
Why is the solubility of haloalkanes in water very low?

CBSE 12th Standard Chemistry Subject Ncert Exemplar MCQ Questions With Solution 2021 - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which of the following statement is not true about amorphous solids?
2)
Considering the formation, breaking and strength of hydrogen bond, predict which of the following mixtures will show a positive deviation from Raoult's law?
3)
Mark the incorrect statements.
4)
The value of colligative properties of colloidal solution are of smalll order in comparison to those shown by true solutions of same concentration because colloidal particles................
5)
Which one of the following statements is correct about the role of substance added in the froth floatation process?

CBSE 12th Standard Chemistry Subject Ncert Exemplar MCQ Questions 2021 Part - II - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
To get an n-type semiconductor from silicon, it should be doped with a substance with valence.......................... .
2)
Colligative properties depend on .............. .
3)
Which of the following statement is not correct about an inert electrode in a cell ?
4)
Mark the incorrect statements.
5)
In physisorption, adsorbent does not show specificity for any particular has because........................ .

CBSE 12th Standard Chemistry Subject Ncert Exemplar MCQ Marks Questions 2021 Part - I - by Archana Singh - Deoghar - May 24, 2021 - View & Read

1)
Which of the following solids is not an electrical conductor?
(a) Mg (s)
(b) TiO (s)
(c) I₂ (s)
(d) H₂O(s)
2)
Low concentration of oxygen in the blood and tissues of people living at high altitude is due to _____________.
3)
An electrochemical cell can behave like an electrolytic cell when --------
4)
According to Arrhenius equation rate constant k is equal to A e.^-Ea/RT Which of the following options represents the graph of In k vs 1/T
5)
In a reaction, catalyst changes...................... .

CBSE 12th Standard Chemistry Subject Biomolecules Chapter Case Study Questions 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
When a protein in its native form, is subjected to physical changes like change in temperature or chemical changes like change in pH, the hydrogenbonds are disturbed. Due to this, globules unfold and helix get uncoiled and protein loses its biological activity. This is called denaturation of protein.
The denaturation causes change in secondary and tertiary structures but primary structures remains intact. Examples of denaturation of protein are coagulation of egg white on boiling, curdling of milk, formation of cheese when an acid is added to milk.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Mark the wrong statement about denaturation of proteins

(a) The primary structure of the protein does not change

(b) Globular proteins are converted into fibrous proteins.

(c) Fibrous proteins are converted into globular proteins.

(d) The biological activity of the protein is destroyed.

(ii) Which structure(s) of proteins remains(s) intact during denaturation process?

(a) Both secondary and tertiary structures	(b) Primary structure only
(c) Secondary structure only	(d) Tertiary structure only

(iii) Cheese is a

(a) globular protein	(b) conjugated protein
(c) denatured protein	(d) derived protein

(iv) Secondary structure of protein refers to

(a) mainly denatured proteins and structure of prosthetic groups

(b) three-dimensional structure, especially the bond between amino acid residues that are distant from each other in the polypeptide chain

(c) linear sequence of amino acid residues in the polypeptide chain

(d) regular folding patterns of continuous portions of the polypeptide chain

2)
Read the passage given below and answer the following questions:
The sequence of bases along the DNA and RNA chain establishes its primary structure which controls the specific properties of the nucleic acid. An RNA molecule is usually a single chain of ribose-containing nucleotide. On the basis of X-ray analysis of DNA, J.D., Watson and F.H.C. crick (shared noble prize in 1962) proposed a three dimensional secondary structure for DNA. DNA molecule is a long and highly complex, spirally twisted, double helix, ladder like structure. The two polynucleotide chains or strands are linked up by hydrogen bonding between the nitrogeneous base molecules of their nucleotide monomers. Adenine (purine) always links with thymine (pyrimidine) with the help of two hydrogen bonds and guanine (purine) with cytosine (pyrimidine) with the help of three hydrogen bonds. Hence, the two strands extend in opposite directions, i.e., are antiparallel and complimentary.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: DNA molecules and RNA molecules are found in the nucleus of a cell.
Reason: There are two types of nitrogenous bases, purines and pyrimidines. Adenine (A) and guanine (G) are substituted purines; cytosine (C), thymine (T) and uracil (U) are substituted pyrimidines
(ii) Assertion: In both DNA and RNA, heterocyclic base and phosphate ester linkages are at C-1^'and C-5^' respectively of the sugar molecule.
Reason: Nucleotides and nucleosides mainly differ from each other in presence of phosphate units.
(iii) Assertion: The backbone ofRNA molecule is a linear chain consisting of an alternating units of a heterocylic base, D-ribose and a phosphate.
Reason: The segment of DNA which acts as the instruction manual for the synthesis of protein is ribose.
(iv) Assertion: The double helical structure of DNA was proposed by Emil Fischer.
Reason: A nucleoside is an N-glycoside of heterocyclic base.
3)
Read the passage given below and answer the following questions:
Proteins are high molecular mass complex biomolecules of amino acids. The important proteins required for our body are enzymes, hormones, antibodies, transport proteins, structural proteins, contractile proteins etc. Except for glycine, all a-amino acids have chiral carbon atom and most of them have L-configuration. The amino acids exists as dipolar ion called zwitter ion, in which a proton goes from the carboxyl group to the amino group. A large number of a-amino acids are joined by peptide bonds forming polypeptides. The pep tides having very large molecular mass (more than 10,000) are called proteins. The structure of proteins is described as primary structure giving sequence of linking of amino acids; secondary structure giving manner in which polypeptide chains are arranged and folded; tertiary structure giving folding, coiling or bonding polypeptide chains producing three dimensional structures and quaternary structure giving arrangement of sub-units in an aggregate protein molecule.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: All amino acids are optically active.
Reason: Amino acids contain asymmetric carbon atoms.
(ii) Assertion: In \(\alpha \) -helix structure, intramolecular H-bonding takes place whereas in \(\beta \) -pleated structure, intermolecular H-bonding takes place.
Reason: An egg contains a soluble globular protein called albumin which is present in the white part.
(iii) Assertion: Secondary structure of protein refers to regular folding patterns of continuos portions of the polypeptide chain.
Reason: Out of 20 amino acids, only 12 amino acids can be synthesised by human body.
(iv) Assertion: The helical structure of protein is stabilised by intramolecular hydrogen bond between -NH and carbonyl oxygen.
Reason: Sanger's reagent is used for the identification of N-terminal amino acid of peptide chain.
4)
Read the passage given below and answer the following questions:
Glucose is known as dextrose because it occurs in nature as the optically active dextrorotatory isomer. It is essential constituent of human blood. The blood normally contains 65 to 110 mg of glucose per 100 mL (hence named Blood sugar). The level may be much higher in diabetic persons. The urine of diabetic persons also contain considerable amount of glucose. In combined form, it occurs in cane sugar and polysaccharides such as starch and cellulose.
Glucose has an aldehyde group (-CHO), one primary alcoholic group (-CH₂OH) and four secondary alcoholic groups (-CHOH) in their structure. Due to the presence five hydroxyl groups (-OH), glucose acetylation. Glucose also undergoes oxidation with mild oxidising agents like bromine water as well as with strong oxidising agents like nitric acid. Since glucose is readily oxidised, it acts as a strong reducing agent and reduces Tollen's reagent and Fehling solution. Glucose exists in two crystalline forms: \(\alpha \) -D-glucose and \(\beta \) -Dglucose undergoes If either of the two forms is dissolved in water and allowed to stand, the specific rotation of the solution changes gradually, until a constant value is obtained. This change is called mutarotation.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: A diabetic person carries a packet of glucose with him always.
Reason: Glucose increases the blood sugar level almost instantaneously.
(ii) Assertion: On oxidation with nitric acid, glucose as well as gluconic acid both yield saccharic acid.
Reason: The pentaacetate of glucose does not react with hydroxylamine indicating the absence of free -CHO group.
(iii) Assertion: Glucose reacts with acetyl chloride to form pentaacetyl glucose.
Reason: The formation of pentaacetyl derivative confirms the presence of five -OH groups in glucose.
(iv) Assertion: A certain compound gives negative test with ninhydrin and positive test with Benedict's solution, the compound is an amino acid.
Reason: Glucose is a monosaccharide.

CBSE 12th Standard Chemistry Subject Amines Chapter Case Study Questions 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
Amines are basic in nature. The basic strength of amines can be expressed by their dissociation constant, K_b or pK_{b.

\(\mathrm{RNH}_{2}+\mathrm{H}_{2} \mathrm{O} \rightleftharpoons \mathrm{RNH}_{3}^{+}+\mathrm{OH}^{-}\)

\(K_{b}=\frac{\left[R \mathrm{NH}_{3}^{+}\right]\left[\mathrm{OH}^{-}\right]}{\left[R \mathrm{NH}_{2}\right]} \text { and } \mathrm{p} K_{b}=-\log K_{b}\)}
Greater the K_b value or smaller the pK_b value, more is the basic strength of amine. Aryl amines such as aniline are less basic than allphatic amines due to the involvement of lone pair of electrons on N-atom with the resonance in benzene. In derivatives of aniline, the electron releasing groups increase the basic strength while electron withdrawing groups decrease the basic strength. The base weakening effect of electron withdrawing group and base strengthening effect of electron releasing group is more marked at p-position than at m-position. o-Substituted aniline is less basic than aniline due to ortho effect and is probable due to combination of electronic and steric effect.
The following questions are multiple choice questions.Choose the most appropriate answer :
(i) Which of the following has lowest pK_b value?

(ii) The strongest base among the following is

(a) C₆H₅NH₂	(b) p-NO₂ - C₆H₄CH₂NH₂
(c) m-NO₂ - C₆H₄NH₂	(d) C₆H₅NH₂

(iii) Maximum pK_b value of


(c) (CH₃CH₂)₂NH	(d) (CH₃)₂NH

(iv) Which of the following statements is not correct?

(a) Methylamine is more basic than NH₃	(b) Amines form hydrogen bonds.
(c) Ethylamine has higher boiling point than propane.	(d) Dimethylamine is less basic than methylamine.

2)
Read the passage given below and answer the following questions:
RCONH₂ is converted into RNH₂ by means of Hoffmann bromamide degradation. During the reaction amide is treated with Br₂ and alkali to get amine. This reaction is used to descend the series in which carbon atom is removed as carbonate ion (CO₃^2-). Hoffmann bromide degradation reaction can be written as :

The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Hoffmann bromamide degradation is used for the preparation of

(a) primary amines (b) secondary amines (c) tertiary amines (d) secondary aromatic amines.

(ii) Which is the rate determining step in Hoffmann bromamide degradation?

(a) Formation of (i) (b) Formation of (ii) (c) Formation of (iii) (d) Formation of (iv).

(iii) Which of the following are used for the conversion of (i) to (ii)?

(a) KBr (b) KBr + CH₃ONa (c) KBr + KOH (d) Br₂ + KOH

(iv) What are the constituent amines formed when the mixture of (i) and (ii) undergoes Hoffmann bromamide degradation?
3)
Read the passage given below and answer the following questions:
Amines are produced when an alcoholic solution of ammonia and an alkyl or a benzyl halide is heated in a sealed tube at 373 K. This reaction is called ammonolysis and usually gives a mixture of primary, secondary and tertiary amines along with some quarternary ammonium salts. This reaction is an example of nucleophilic substitution reaction in which ammonia acts as a nucleophile due to the presence of a lone pair of electrons on the nitrogen atom. However this method cannot be used for the preparation of aryl amines. One of the most convenient methods for the preparation of aryl amines is reduction of nitro compounds. Aryl amines can also be prepared by reduction of nitrites or Gabriel phthalimide synthesis.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement. .
(i) Assertion: Ammonolysis of alkyl halides only produces 2^o amines.
Reason: Ammonolysis of alkyl halides involves the reaction between alkyl halides and alcoholic ammonia.
(ii) Assertion: Ammonolysis method cannot be used for the preparation of aryl amines.
Reason: Aryl halides are much less reactive than alkyl halides towards nucleophilic substitution reaction.
(iii) Assertion: Ammonolysis can be used to prepare pure primary amines.
Reason: Ammonolysis of haloalkanes lead to multiple ammonium salts.
(iv) Assertion: Aromatic 1^p amines can not be prepared by Gabriel phthalimide synthesis.
Reason: Aryl halides do not undergo nucleophilic substitution with anion formed by phthalimide.
4)
Read the passage given below and answer the following questions:
Aniline activates the benzene ring by increasing electron density at ortho- and para-positions. Hence, it is o-, p-directing. -NH₂group strongly activates the ring therefore it is difficult to stop the reaction at monosubstitution stage. Among electrophilic substitution reaction, direct nitration of aniline is not done to get o- and p-nitroaniline because lone pair of electrons present at nitrogen atom will accept proton from nitrating mixture to give anilinium ion which is meta-directing. Aniline with NaNO₂ and HCl forms benzene diazonium chloride at very low temperature. Aromatic amines react with nitrous acid to form a yellow oily liquid known as N-nitrosoamines.
In these questions ( i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Nitrating mixture used for carrying out nitration of benzene consists of cone. conc. HNO₃ +conc. H₂SO₄ .
Reason:In presence of H₂SO₄ , HNO₃ acts as a base and produces NO₂⁺ ions.
(ii) Assertion: Anilinium chloride is more acidic than ammonium chloride.
Reason: Anilinium ion is not resonance-stabilised.
(iii) Assertion: Nitrobenzene can be prepared from benzene by using mixture of conc. HNO₃ and conc. H₂SO₄ .
Reason: In the mixture,H₂SO₄ act as a acid.
(iv) Assertion: In strongly acidic solution, aniline becomes less reactive towards electrophilic reagents.
Reason: The amino group being completely protonated in strongly acidic solution, the lone pair of electrons on the nitrogen is no longer available for resonance.

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids Chapter Case Study Questions 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
(A), (B) and (C) are three non-cyclic functional isomers of a carbonyl compound with molecular formula C₄H₈O. Isomers (A) and (C) give positive Tollen's test whereas isomer (B) does not give Tollen's test but gives positive iodoform test. Isomers (A) and (B) on reduction with Zn(Hg)/conc. HCI give the same product (D).
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Compound A is

(ii) Compound (B) can be obtained by

\({ (a) } \ \mathrm{CH}_{3}-\mathrm{C} \equiv \mathrm{C}-\mathrm{CH}_{2}-\mathrm{CH}_{3} \frac{\text { dil. } \mathrm{H}_{2} \mathrm{SO}_{4}+\mathrm{HgSO}_{4}}{333 \mathrm{~K}}\)	\((b) \ \left(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COO}\right)_{2} \mathrm{Ca} \stackrel{\text { Dry distill }}{\longrightarrow}\)
\((c) \ \mathrm{CH}_{3}-\mathrm{C} \equiv \mathrm{C}-\mathrm{CH}_{3} \frac{\mathrm{B}_{2} \mathrm{H}_{6} / \mathrm{THF}}{\mathrm{H}_{2} \mathrm{O}_{2} / \mathrm{NaOH}}\)	\((d) \ \mathrm{CH}_{3}-\mathrm{CH}=\mathrm{CH}-\mathrm{CH}_{3} \frac{\mathrm{O}_{3}}{\mathrm{Zn} / \mathrm{H}_{2} \mathrm{O}}\)

(iii) Out of (A), (B) and (C) isomers, which one is least reactive towards addition of HCN ?

(a) A	(b) B
(c) C	(d) All are equally reactive

(iv) What will be the product when (B) reacts with ethylene glycol in presence ofHCI gas?

2)
Read the passage given below and answer the following questions:
Aldehydes and ketones are reduced to primary and secondary alcohols respectively by NaBH₄ or LiAIH₄ as well as catalytic hydrogenation. The carbonyl group of aldehydes and ketones is reduced to group on treatment with Zn-Hg and cone, HCI (Clemmensen reduction) or with hydrazine followed by NaOH or KOH in highly boiling solvent such, as ethylene glycol (Wolff- Kishner reduction).
Aldehydes differ from ketones in their oxidation reactions. Aldehydes are easily oxidised to carboxylic acids on treatment with HNO₃, KMnO₄, K₂Cr₂O₇ etc. Even mild oxidising agents mainly Tollens' reagent and Fehling's solution also oxidise aldehydes. Ketones are generally oxidised under vigorous conditions i.e., strong oxidising agents and at elevated temperatures, to give mixture of carboxylic acids having lesser number of C-atoms than the parent ketone.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Which of the following cannot be made by reduction of ketone or aldehyde with NaBH₄ in methanol?

(a) 1-Butanol (b) 2-Butanol

(c) 2-Methyl-I-propanol (d) 2-Methyl-2-propanol

(ii) The carbonyl compound producing an optically active product by reaction with LiAlH₄ is

(a) propanone (b) butanone (c) 3-pentanone (d) benzophenone

(iii) A substance C₄H₁₀O(X) yields on oxidation a compound C₄H₈O which gives an oxime and a positive iodoform test. The substance X on treatment with cone. H2S04 gives C4Hs. The structure of the compound (X) is

(a) CH₃CH₂CH₂CH₂OH (b) CH₃CH(OH)CH₂CH₃

(c) (CH₃)₃COH (d) CH₃CH₂-O-CH₂CH₃

(iv) In the oxidation of by acidified K₂Cr₂O₇, the products are
3)
Read the passage given below and answer the following questions:
Carboxylic acids having an a-hydrogen atom when treated with chlorine or bromine in the presence of small amount of red phosphorus gives a-halo carboxylic acids. The reaction is known as Hell- Volhard-Zelinsky reaction.

When sodium salt of carboxylic acid is heated with soda lime it loses carbon dioxide and gives hydrocarbon with less number of C-atoms.

In these questions (i - iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: (CH₃)₃CCOOH does not give H.V.Z reaction.
Reason: (CH₃)₃CCOOH does not have \(\alpha\)-hydrogen atom.
(ii) Assertion: H.V.Z. reaction involves the treatment of carboxylic acids having \(\alpha\)-hydrogens with Cl₂ or Br₂in presence of small amount of redphosphorus.
Reason : Phosphorus reacts with halogens to form phosphorus trihalides.
(iii) Assertion: C₆H₅COCH₂COOH undergoes decarboxylation easily than C₆H₅COCOOH.
Reason : C₆H₅COCH₂COOH is a 13-ketoacid.
(iv) Assertion: On heating 3-methylbutanoic acid with soda lime, isobutane is obtained.
Reason: Soda lime is a mixture of NaOH + CaO in the ratio 3 : 1.
4)
Read the passage given below and answer the following questions:
Fehling's reagent: Fehling's reagent is a mixture of two solutions. Fehling's solution A is aqueous copper sulphate solution. Fehling's solution B is alkaline sodium potassium tartarate (Rochelle salt).

It is a mild oxidising agent. It is weaker than Tollens' reagent. It oxidises only aliphatic aldehydes to carboxylate ions and'itself gets reduced to reddish brown precipitate of cuprous oxide.
Aromatic aldehydes do not respond to Fehling's test. This reaction is used for the test of aliphatic aldehydes known as Fehling's reagent test.
In these questions ( i - iv) a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Fehling's solution can be used to distinguish between acetaldehyde and acetone.
Reason: Fehling's reagent is a mixture of two solutions.
(ii) Assertion: Aromatic aldehydes can be distinguished from aliphatic aldehydes by Fehling's solution.
Reason: Aromatic 'aldehydes reduce Fehling's solution, but aliphatic aldehydes do not.
(iii) Assertion: CH₃CHO and C₆H₅CH₂CHO cannot be distinguished chemically by Fehling's solution.
Reason: CH₃CHO and C₆H₅CH₂CHO can be distinguished by iodoform test.
(iv) Assertion: Formaldehyde, when heated with Fehling's reagent produces a reddish brown ppt. of Cu.
Reason: Fehling's reagent oxidises formaldehyde to formate ion.
5)
Read the passage given below and answer the following questions:
Aldehydes and ketones undergo nucleophilic addition reactions .

Carbonyl carbon is electron deficient hence acts as an electrophile. Nucleophile attacks on the electrophilic carbon atom of the carbonyl group from a direction perpendicular to the plane of the molecule.

In this process, hybridisation of carbon atom changes from sp² to sp³ and a tetrahedral alkoxide ion is formed as intermediate. This intermediate captures proton from the reaction medium to give the neutral product. Aldehydes are generally more reactive than ketones in nucleophilic addition reactions.
In these questions ( i - iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Benzaldehyde is more reactive than ethanal towards nucleophilic attack.
Reason: The overall effect of -land +R effect of phenyl group decreases the electron density on the carbon atom of ＞C=O group in benzaldehyde
(ii) Assertion: (CH₃)₃CCOC(CH₃)₃ and acetone can be distinguished by the reaction with NaHSO₃.
Reason: HSO₃ is the nucleophile in bisulphite addition.
(iii) Assertion: Ease of nucleophilic addition of the compounds (I). CH₃CHO(II) and CH₃COCH₃(III) is I > II > III.
Reason : Aldehydes and ketones undergo nucleophilic addition reactions.
(iv) Assertion: is more reactive towards nucleophilic addition reaction than
Reason : Reactivity of carbonyl group is due to electrophilic nature of carbonyl carbon.

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers Chapter Case Study Questions 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)
Read the passage given below and answer the following questions:
Reimer- Tiemann reaction introduces an aldehyde group, on aromatic ring of phenol, ortho to the hydroxyl group. This is a general method for the synthesis of substituted salicylaldehydes as depicted below.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Reimer-Tiemann reaction is an example of

(a) nucleophilic substitution reaction (b) electrophilic substitution reaction

(c) nucleophilic addition reaction (d) electrophilic addition reaction

(ii) Which of the following reagents is used in the given reaction in steps I?

(a) aq. NaOH + CH₃CI (b) aq. NaOH + CH₂Cl₂ (c) aq. NaOH + CHCl₃ (d) aq. NaOH + CCl₄

(iii) The structure of the intermediate [A] is

(iv) When phenol reacts with chloroform in presence of KOH, the product formed is

(a) salicylic acid (b) salicylaldehyde (c) both (a) and (b) (d) none of these.
2)
Read the passage given below and answer the following questions:
Dehydration of alcohols can lead to the formation of either alkenes or ethers. This dehydration can be carried out either with protonic acids such as cone. H₂SO₄, H₃PO₄ or catalysts such as anhydrous ZnCl₂ or Al₂O₃. When primary alcohols are heated with cone. H₂SO₄ at 433-443 K, they undergo intramolecular dehydration to form alkenes. Secondary and tertiary alcohols undergo dehydration under milder conditions. The ease of dehydration of alcohols follows the order: 3° > 2° > 1°. The dehydration of alcohols always occurs in accordance with the Saytzeffs rule. Primary alcohols when heated with protic acid at 413 K, gives dialkyl ether.

The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Which one of the following alcohols undergoes acid-catalysed dehydration to alkenes most readily?

(a) (CH₃)₂CHCH₂OH (b) (CH₃)₃COH (c) CH₃CHOHCH₃ (d) CH₃CH₂CH₂OH

(ii) Dehydration of alcohol is an example of which type of reaction?

(a) Substitution (b) Elimination (c) Addition (d) Rearrangement

(iii) The alcohol which does not give a stable compound on dehydration is

(a) ethyl alcohol (b) methyl alcohol (c) n-propyl alcohol (d) n-butyl alcohol

(iv) products.
The most stable product(s) is/are

(c) both (a) and (b) (d) none of these.
3)
Read the passage given below and answer the following questions:
Williamson's synthesis is used for the preparation of symmetrical as well as unsymmerical ether. It is S_N2 reaction mechanism. In Williamson's synthesis, 1° alkyl halide are used for preparation of ethers because 2° and 3°alkyl halide give alkene: Ethers are cleaved by hydrogen halides to alcohol and alkyl halide where alkyl halide is corresponding to that alkyl which has less number of carbon atom (it is because ofless steric hindrance). In polar media unsymmetrical ether like tertiary butyl ethyl ether gives ethyl alcohol and tertiary butyl halide as reaction proceeds via carbocation.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Rate of reaction of alkyl halide in Williamson's synthesis reaction is 1°RX> 2°RX > 3°RX.
Reason: It is a type of bimolecular substitution reaction (S_N2).
(ii) Assertion: t-Butyl methyl ether is not prepared by the reaction of t-butyl bromide with sodium methoxide.
Reason: Sodium methoxide is a weak nucleophile.
(iii) Assertion: When isopropyl bromide is treated with sodium isopropoxide, di-isopropyl ether is obtained as a major product. .
Reason: With secondary alkyl halides, both substitution and elimination occur.
(iv) Assertion: Both symmetrical arid unsymmetrical ethers can be prepared by Williamson's synthesis.
Reason: Williamson's synthesis is an example of nucleophilic substitution reaction.
4)
Read the passage given below and answer the following questions:
Due to intermolecular hydrogen bonding, the boiling points of alcohols and phenols are much higher than those of corresponding haloalkanes, haloarenes, aliphatic and aromatic hydrocarbons. Among isomeric alcohols, the boiling points follow the order : primary > secondary > tertiary. Boiling points of ethers are much lower than those of isomeric alcohols. The solubility of alcohols in water decreases as the molecular mass of alcohols increases. Amongst isomeric alcohols solubility increases with branching. The solubility of phenols in water is much lower than that of alcohols. Lower ethers such as dimethyl ether and ethyl methyl ether are soluble in water, but the solubility decreases as the molecular mass increases.
In these questions (i-iv) a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Alcohols have higher boiling points than ethers of comparable molecular masses.
Reason: Alcohols and ethers are isomeric in nature.
(ii) Assertion: The solubility of phenols in water is much lower than that of alcohols.
Reason: Phenols do not form H-bonds with water.
(iii) Assertion : Among n-butane, ethoxyethane,1-propanol and 2-propanol, the increasing order of boiling points is,1-butanol < 1-propanol < ethoxyethane < n-butane.
Reason: Boiling point increases with increase in molecular mass.
(iv) Assertion: Dimethyl ether and diethylether are soluble in water.
Reason: As the molecular mass increases, solubility of ethers in water decreases.
5)
Read the passage given below and answer the following questions:
Lucas test is a test to differentiate between primary, secondary and tertiary alcohols. This test consists of treating an alcohol with Lucas reagent, and turbidity, due to the formation of insoluble alkyl chloride, is observed. Lucas test is based on the difference in reacting of three classes of alcohols with hydrogen chloride via S_N1 reaction. The different reactivity reflects the differing ease of formation of the corresponding carbocations.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Equimolar mixture of conc. HCI and anhydrous ZnCl₂ is called Lucas' reagent.
Reason : Lucas' reagent can be used to distinguish between methanol and ethanol.
(ii) Assertion: 2-Methyl-2-butanol gives no turbidity with Lucas' reagent at room temperature.
Reason: It is a 3° alcohol
(iii) Assertion: Amongst the compounds, H₂C =CHCH₂OH (I), C₆H₅OH (II), CH₃CH₂CH₂OH (III) and (CH₃)₃COH (IV), only (IV) reacts with Lucas' reagent at room temperature.
Reason : Tertiary alcohol gives turbidity immediately with Lucas' reagent.
(iv) Assertion: Lucas test can be used to distinguish between 1-propanol and 2-propanol.
Reason : Lucas test is based upon the difference in reactivity of primary, secondary and tertiary alcohols with conc. HCI and anhyd. ZnCI₂.

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes Chapter Case Study Questions 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)
Read the passage given below and answer the following questions:
Haloarenes are less reactive than haloalkanes. The low reactivity of haloarenes can be attributed to
(i) resonance effect
(ii) Sp²hybridisation of C - X bond
(iii) polarity of C - X bond
(iv) instability of phenyl cation (formed by self-ionisation ofhaloarene)
(v) repulsion between the electron rich attacking nucleophiles and electron rich arenes.
Reactivity of haloarenes can be increased or decreased by the presence of certain groups at certain positions for example, nitro (-NO₂) group at olp positions increases the reactivity of haloarenes towards nucleophilc substitution reactions.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Aryl halides are less reactive towards nucleophilic substitution reaction as compared to alkyl halides due to

(a) the formation ofless stable carbonium ion (b) resonance stabilisation

(c) larger carbon-halogen bond (d) inductive effect.

(ii) Which of the following aryl halides is the most reactive towards nucleophilic substitution?

(iii) Which one of the following will react fastest with aqueous NaOH?

The reactivity of the compounds (i) MeBr, (ii) PhCH₂Br, (iii) MeCI, (iv) p- MeOC₆H₄Br decreases as

(a) (i) > (ii) >(iii) > (iv) (b) (iv) > (ii) >(i) > (iii)

(c) (iv) > (iii) >(i) > (ii) (d) (ii) > (i) > (iii) > (iv)

2)

Read the passage given below and answer the following questions:
In haloalkanes, when a nucleophile stronger than the halide ion approaches the positively charged carbon atom of an alkyl halide, the halogen atom along with its bonding electron pair gets displaced and a new bond with the carbon and the nucleophile is formed. These reactions are called nucleophilic substitution reactions.

In these reactions the atom or group of atoms which loses its bond from carbon and takes on an additional pair of electrons is called leaving group. Halide ions are good leaving groups. Some important nucleophilic substitution reactions of haloalkanes with common nucleophiles are given in the table below.

	Reagent	Nudeophile (Nu^-)	Substitution product R-Nu	Class of main product
1.	NaOH or KOH or moist Ag₂O	^-OH	ROH	Alcohol
2.	H₂O	H₂O	ROH	Alcohol
3.	NaI	I^-	R-I	Alkyl iodide
4.	R'NH₂	\(R^{\prime} \ddot{\mathrm{N}} \mathrm{H}_{2}\)	RNHR'	Sec. amine
5.	KCN	\(\overline{\mathrm{C}} \equiv \mathrm{N}:\)	RCN	Nitrile (cyanide)
6.	KNO₂	O=N-O^-	R-O-N=O	Alkyl nitrite

In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason' is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Alkyl halides are hydrolysed to alcohols by moist silver oxide.
Reason: RCI is hydrolysed to ROH easily but reactions slow down on addition of KI.
(ii) Assertion : Alkyl halides form alkenes when heated above 300°C.
Reason: CH₃CH₂I reacts slowly with strong base as compared to CD₃CH₂I.
(iii) Assertion : RBr reacts with AgNO₂ to give nitro alkane.
Reason: Silver nitrite (AgNO₂) is an ionic compound, therefore the negative charge on nitrogen is the attacking site.
(iv) Assertion: The nucleophilic substitution of vinyl chloride is difficult than ethyl chloride.
Reason: Vinyl group is electron donating group.

3)
Read the passage given below and answer the following questions:
When a chemical reaction involves bond cleavage or bond formation at an asymmetric carbon atom, three different products may be formed. For example, during the substitution of a group X by Y in the following reaction, the three possible products may be shown below:

(i) If B is the only product, the process is called retention of configuration because B has the same configuration as the starting reactant (A).
(ii) If C is the only product, the process is called inversion of configuration because C has the configuration opposite to the starting reactant (A).
(iii) If an equimolar mixture of B and C (i.e., a 50 : 50 mixture) is formed, then the process is called racemisation and the product is optically inactive because one isomer will rotate the light in the direction opposite to another.
In these questions ( i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correctstatements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: A reaction is said to be stereospecific if a particular stereoisomer of the reactant produces a specific stereoisomer of the product.
Reason: Bromination of cis-2-butene gives meso-2, 3-dibromobutane which is stereospecific
(ii) Assertion: Addition of Br₂ to cis-but-2-ene is stereoselective.
Reason: S_N2 reactions are stereospecific as well as stereoselective.
(iii) Assertion: Optically active 2-iodobutane on treatment with NaI in acetone undergoes recemization.
Reason: Repeated Walden inversions on the reactant and its product eventually gives a racemic mixture.
(iv) Assertion: S_N2 reaction of an optically active alkyl halide with an aqueous solution of KOH always gives an alcohol with opposite sign of rotation.
Reason: S_N2 reactions always proceed with inversion of configuration.
4)
Read the passage given below and answer the following questions:
The order of reactivity towards S_N1 reaction depends upon the stability of carbocation in the first step. Greater the stability of the carbocation, greater will be its ease of formation from alkyl halide and hence faster will be the rate of the reaction. As we know, 3° carbocation is most stable, therefore, the tert-alkyl that halides will undergo S_N1 reaction very fast. For example, it has been observed that the reaction (CH₃)₃CBr with OH^- ion to give 2-methyl-2-propanol is about 1 million times as fast as the corresponding reaction of the methyl bromide to give methanol.
The primary alkyl halides always react predominantly by S_N2 mechanism. On the other hand, the tertiary alkyl halides react predominantly by S_N1 mechanism. Secondary alkyl halides may react by either mechanism or by both the mechanisms without much preference depending upon the nature of the nucleophile and solvent.
In these questions ( i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Low concentration of nucleophile favours S_N1mechanism.
Reason: 2° alkyl halides are less reactive than 1° towards S_N1 reactions.
(ii) Assertion: Polar solvent slows down S_N2reactions.
Reason: CH₃-Br is less reactive than CH₃Cl.
(iii) Assertion: Benzyl bromide when kept in acetone- water it produces benzyl alcohol.
Reason: The reaction follows S_N2 mechanism.
(iv) Assertion: Rate of hydrolysis of methyl chloride to methanol is higher in DMF than in water.
Reason: Hydrolysis of methyl chloride follows second order kinetics.
5)
Read the passage given below and answer the following questions:
The aryl halides are relatively less reactive towards nucleophilic substitution reactions as compared to alkyl halides. This low reactivity can be attributed to the following factors:
1. The C - X bond in halobenzene has a partial double bond character due to involvement of halogen electrons in resonance with benzene ring.
2. The C - X bond in aryl halides is less polar as compared to that in alkyl halides as sp² hyridised carbon is more electronegative than sp³ hybridised carbon.
In these questions ( i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Primary benzylic halides are more reactive than primary alkyl halides towards S_N1 reactions.
Reason: Reactivity depends upon the nature of the nucleophile and the solvent.
(ii) Assertion : is more reactive than towards nucleophilic substitution reactions.
Reason: Tertiary alkyl halides react predominantly by S_N1 mechanism.
(iii) Assertion: Chlorobenzene is more reactive than p-chloroanisole to nucleophilic substitution reactions.
Reason: Greater the stability of'carbanion, greater is its ease of formation and hence, more reactive is the aryl halide.
(iv) Assertion: Chlorobenzene is less reactive than benzene towards the electrophilic substitution reaction.
Reason: Resonance destabilises the carbo cation.

CBSE 12th Standard Chemistry Subject Coordination Compounds Chapter Case Study Questions 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
Metal carbonyl is an example of coordination compounds in which carbon monoxide (CO) acts as ligand. These are also called homoleptic carbonyls. These compounds contain both \(\sigma\) and \(\pi\) character. Some carbonyls have metal-metal bonds. The reactivity of metal carbonyls is due to (i) the metal centre and (ii) the CO ligands. CO is capable of accepting an appreciable amount of electron density from the metal atom into their empty \(\pi\) or \(\pi\)^* orbitals. These types ofligands are called \(\pi\)-accepter or \(\pi\)-acid ligands. These interactions increases the Δ_o value.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) What is the oxidation state of metal in [ Mn₂(CO)₁₀] ?

(a) +1

(b) -1

(c) +2

(d) 0

(ii) Among the following metal carbonyls, the C - O bond order is lowest in

(a) \(\left[\mathrm{Mn}(\mathrm{CO})_{6}\right]^{+}\)

(b) \(\left[\mathrm{Fe}(\mathrm{CO})_{5}\right]\)

(c) \(\left[\mathrm{Cr}(\mathrm{CO})_{6}\right]\)

(d) \(\left[\mathrm{V}(\mathrm{CO})_{6}\right]^{-}\)

(iii) The oxidation state of cobalt in K [CO(CO)₄] is

(a) +1

(b) +3

(c) -1

(d) 0

(iv) Structure of decacarbonyl manganese is

(a) trigonal bipyramidial

(b) octahedral

(c) tetrahedral

(d) square pyramidal.

2)
Read the passage given below and answer the following questions:
Werner, a Swiss chemist in 1892 prepared and characterised a large number of coordination compounds and studied their physical and chemical behaviour. He proposed that, in coordination compounds, metals possess two types of valencies, viz. primary; valencies, which are normally ionisable and secondary valencies which are non-ionisable. In a series of compounds of cobalt (III) chloride with ammonia, it was found that some of the chloride ions could be precipitated as AgCI on adding excess of AgNO₃ solution in cold, but some remained in solution. The number of ions furnished by a complex in a solution can be determined by precipitation reactions. The measurement of molar conductance of solutions of coordination compounds helps to estimate the number of ions furnished by the compound in solution.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Assertion: The complex [Co(NH₃)₃CI₃] does not give precipitate with silver nitrate solution.
Reason: The given complex is non-ionisable.
(ii) Assertion: The complex [Co(NH₃)₄Cl₂]Cl gives precipitate corresponding to 2 mol of AgCl with AgNO₃ solution.
Reason: It ionises as [Co(NH₃)₄Cl₂]⁺ + Cl^-
(iii) Assertion: 1 mol of [CrCl₂CH₂O)₄]Cl· 2H₂O will give 1mol of AgCl on treating with AgNO_3.
Reason: Cl^- ions satisfying secondary valanceis will not be precipitated.
(iv) Assertion: CoCl₃·3NH₃ is not conducting while CoCl₃·5NH₃ is conducting.
Reason: The complex of CoCl₃·3NH₃ is [ CoCl₃(3NH₃)₃] while that of CoCl₃·5NH₃ is [CoCl₃(3NH₃)₅]Cl₂.
3)
Read the passage given below and answer the following questions:
Arrangement of ligands in order of their ability to cause splitting Δ is called spectrochemical series. Ligands which cause large splitting (large Δ ) are called strong field ligands while those which cause small splitting (small Δ) are called weak field ligands. When strong field ligands approach metal atomlion, the value of Δ_o is large, so that electrons are forced to get paired up in lower energy t_2g orbitals. Hence, a low-spin complex is resulted from strong field ligand. When weak field ligands approach metal atom/ion, the value of Δ_o is small, so that electrons enter high energy e_g orbitals rather than pairing in low energy t_2g orbitals. Hence, a high-spin complex is resulted from weak field ligands. Strong field ligands have tendency to form inner orbital complexes by forcing the electrons to pair up. Whereas weak field ligands have tendency to form outer orbital complex because inner electrons generally do not pair up.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: In tetrahedral coordination entity formation, the d orbital splitting is inverted and is smaller as compared to the octahedral field splitting.
Reason: Spectrochemical series is based on the absorption of light by complexes with different ligands.
(ii) Assertion: F^- ion is a weak field ligand and forms outer orbital complex.
Reason: F^- ion cannot force the electrons of d_z2 and d_{x²- y²}orbitals of the inner shell to occupy d_xy, d_yz and d_zx orbitals of the same shell.
(iii) Assertion: The crystal field model is successful in explaining the formation, structures, colour and magnetic properties of coordination compounds.
Reason: In spectrochemical series, ligands are arranged in a series of increasing field strength.
(iv) Assertion: NF₃ is a weaker ligand than N(CH₃)_3.
Reason: NF₃ ionizes to give F^- ions in aqueous solution.
4)
Read the passage given below and answer the following questions:
Ligands are atoms or ions which can donate electrons to the central atoms. Ligands can be monodentate, bidentate or polydentate as well. Few ligands can coordinate with the central atom through more than one site, these are called ambidentate ligands. When a di- or polydentate ligand uses its two or more donor atoms to bind a single metal ion, it is said to be a chelating ligand.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Glycinate ion is an example of mono dentate ligand.
Reason: Glycinate contains Nand O as donor atoms
(ii) Assertion: Oxalate ion is a bidentate ligand.
Reason: Oxalate ion has two donor atoms
(iii) Assertion: A chelating ligand must possess two or more lone pairs at such a distance that it may form suitable strain free 5 and 6 membered rings with the metal ion.
Reason: H₂N- NH₂ is a chelating ligand.
(iv) Assertion: In Zeise's salt coordination number of Pt is five.
Reason: Ethene is a monodentate ligand.
5)
Read the passage given below and answer the following questions:
For understanding the structure and bonding in transition metal complexes, the magnetic properties are very helpful. Low spin complexes are generally diamagnetic because of pairing of electrons, whereas high spin complexes are usually paramagnetic because of presence of unpaired electrons. Larger the number of unpaired electrons, stronger will be the paramagnetism. However magnetic behaviour of a complex can be confirmed from magnetic moment measurement. Magnetic moment \(\mu=\sqrt{n(n+2)} \text { B.M. }\)where n = number of unpaired electrons. Greater the number of unpaired electrons, more will be the magnetic moment.
In these questions ( i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Both [Cr(H₂O)₆]²⁺ and [FeH₂O)₆]²⁺ have same magnetic moment.
Reason: Number of unpaired electrons in Cr²⁺and Fe²⁺ are same.
(ii) Assertion: [Fe(H₂O)₅NO]SO₄ is paramagnetic.
Reason: The Fe in [Fe(H₂O)₅NO]SO₄ has three unpaired electrons.
(iii) Assertion: [Co(en)₃]³⁺ is paramagnetic.
Reason: It is an inner orbital complex.
(iv) Assertion: [Ni(CN)₄]^2- is diamagnetic complex.
Reason: It involves dsl hybridisation and there is no unpaired electron.

CBSE 12th Standard Chemistry Subject The p-Block Elements Chapter Case Study Questions 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)
Read the passage given below and'answer the following questions :
Ozone is an unstable, dark blue diamagnetic gas. It absorbs the UV radiation strongly, thus protecting the people on earth from the harmful UV-radiation from the sun. The use of chlorofluorocarbon (CFC) in aerosol and refrigerators and their subsequent escape into the atmosphere, is blamed for making holes in the ozone layer over the Antarctica. Ozone acts as a strong oxidising agent in acidic and alkaline medium. For this property, ozone is used as a germicide and disinfectant for sterilizing water. It is also used in laboratory for the ozonolysis of organic compounds and in industry for the manufacture of potassium permanganate, artificial silk, etc
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Which of the following statements is not correct for ozone?

(a) It oxidises lead sulphide (b) It oxidises potassium iodide

(c) It oxidises mercury. (d) It cannot act as bleaching agent in dry state.

(ii) Ozone reacts with moist iodine gives

(a) HI (b) HIO₃ (c) I₂O₅ (d) I₂O₄

(iii) Ozone acts as an oxidising agent due to

(a) liberation of nascent oxygen (b) liberation of oxygen gas

(c) both (a) and (b) (d) none of these

(iv) The colour of ozone molecule is

(a) white (b) blue (c) pale green (d) pale yellow.
2)
Read the passage given below and answer the following questions :
Chlorine is a greenish yellow gas with pungent and suffocating odour. With dry slaked lime, it gives bleaching powder. Bleaching powder is a mixture of calcium hypochlorite and basic calcium chloride :
[Ca(OCI)_2. CaCl₂ ·Ca(OH)₂· 2 H₂O].
The amount of chlorine obtained from a sample of bleaching powder by the treatment with excess of dilute
acids or CO₂ is called available chlorine. Chlorine is a powerful bleaching agent. Bleaching effect of chlorine is permanent.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Chlorine gas reacts with_____to form bleaching powder

(a) Ca(OH)₂ (b) CaCl₂

(c) CaSO₄ (d) dry CaO

(ii) Chlorine reacts with cold and dilute alkali to form

(a) chloride (b) hypochlorite (c) chlorate (d) both (a) and (b)

(iii) Chlorine is used as a bleaching agent. The bleaching action is due to

(a) oxidation (b) chlorination (c) hydrogenation (d) reduction

(iv) Bleaching powder contains a salt of an oxoacid as one of its components. The anhydride of that oxoacid is

(a) Cl₂0 (b) Cl₂O₇ (c) CIO₂ (d) Cl₂O₆

3)

Read the passage given below and answer the following questions :
The halogen elements show great resemblances to one another in their chemical behaviour and properties of their compounds with other elements. There is, however, a progressive change in properties from F through Cl, Br, and I to At. F is most reactive among the halogens and infact, from all other elements and it has certain other properties that set it apart from the other halogens.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(b) Assertiqn and reason both are correct statements but reason is not correct explanation for assertion.

(c) Assertion is correct statement but reason is wrong statement

(d) Assertion is wrong statement but reason is correct statement.

(i) Assertion: F₂ has high reactivity.
Reason: F₂ has low bond dissociation enthalpy
(ii) Assertion: The bond between F - F is weaker than between Cl - Cl.
Reason : Atomic size of F is smaller than that of Cl.
(iii) Assertion: F atom has less negative electron affinity than Cl atom.
Reason: Additional electrons are repelled more effectively by 3p- electrons in Cl than by 2p- electrons in F atom.
(iv) Assertion : Fluorine is strongest oxidising agent in halogens.
Reason : It displaces other halogens from its aqueous solution.

4)
Read the passage given below and answer the following questions :
All the elements of group 16 form hydrides : H₂O, H₂S, H₂Se, H₂Te and H₂Po. All these hydrides have angular structure which involves sp3 hybridisation of the central atom. All hydrides are volatile. The volatility increases from H₂O to H₂S and then decreases. All hydrides are weakly acidic in character. The increase in acidic characterfrom H₂O to H₂Te is a result of the decrease in the 1 H- E (where E = 0, S, Se, Te, Po) bond dissociation enthalpy from H₂O to H₂Te. All the hydrides except water are reducing agents. The reducing property of these hydrides increases from H₂S to H₂Te.
In these questions ( i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement
(i) Assertion: Water has high boiling -point.
Reason: Water molecules are associated with hydrogen bonding.
(ii) Assertion: H₂Te has less acidic character than H₂S.
Reason: Bond dissociation enthalpy of H - Te is less than H - S.
(iii) Assertion: Reducing nature of hydrides of group-16 elements increases as the atomic number of central
atom increases.
Reason : Due to strong force of attraction of H - E bond.
(iv) Assertion: H₂O is the only hydrides of the chalcogens which is liquid.
Reason : In ice each a-atom is surrounded by 4H -atoms.

CBSE 12th Standard Chemistry Subject Chemical Kinetics Chapter Case Study Questions 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)
Read the passage given below and answer the following questions :
The half-life of a reaction is the time required for the concentration of reactant to decrease by half, i.e.,

\([A]_{t}=\frac{1}{2}[A]\)
For first order reaction,
\(t_{1 / 2}=\frac{0.693}{k}\) this means t_1/2 is independent of initial concentration. Figure shows that typical variation of concentration of reactant exhibiting first order kinetics. It may be noted that though the major portion of the first order kinetics may be over in a finite time, but the reaction will never cease as the concentration of reactant will be zero only at infinite time
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) A first order reaction has a rate constant k = 3.01 x 10^-3 is. How long it will take to decompose half of the reactant?

(a) 2.303 s (b) 23.03 s (c) 230.3 s (d) 2303 s

(ii) The rate constant for a first order reaction is 7.0x 10^-4s^-1. If initial concentration of reactant is 0.080 M, what is the half life of reaction?

(a) 990 s (b) 79.2 s (c) 12375 s (d) 10.10 x 10^-4s

(iii) For the half-life period of a first order reaction, which one of the following statements is generally false?

(a) It is independent of initial concentration. (b) It is independent of temperature.

(c) It decreases with the introduction of a catalyst (d) None of these

(iv) The rate of a first order reaction is 0.04 mol L^-1 s^-1 at 10 minutes and 0.03 mol L^-1 s^-1at 20 minutes after initiation. The half-life of the reaction is

(a) 4.408 min (b) 44.086 min (c) 24.086 min (d) 2.408 min

2)

Read the passage given below and answer the following questions :
The following reaction, \(A_{(g)} \stackrel{\Delta}{\longrightarrow} P_{(g)}+Q_{(g)}+R_{(g)}\) follows first order kinetics. The half-life period of this reaction is 69.3 s at 500°C. The gas A is enclosed in a container at 500°C and at a pressure of 0.4 atm
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The rat constant for the reaction is

(a) 0.4 s^-1

(b) 0.02 s^-1

(c) 0.01 s^-1

(d) 0.3 s^-1

(ii) The total pressure of the system after 230 s will be

(a) 2.15 atm

(b) 1.12 atm

(c) 0.4 atm

(d) 3.08 atm

(iii) The plot of ln[A] vs t will be

(a) linear with slope = k	(b) linear with intercept = In[A]_o
(c) linear with slope = In[A]_o	(d) linear with intercept = [A]₀

(iv) Which of the following is not an example of first order reaction?

(a) \(\mathrm{C}_{2} \mathrm{H}_{4(g)}+\mathrm{H}_{2(\mathrm{~g})} \rightarrow \mathrm{C}_{2} \mathrm{H}_{6(\mathrm{~g})}\)	(b) \(2 \mathrm{~N}_{2} \mathrm{O}_{5(g)} \rightarrow 4 \mathrm{NO}_{2(g)}+\mathrm{O}_{2(g)}\)
(c) \(2 \mathrm{NH}_{3(g)} \frac{\mathrm{Pt}}{\Delta} \mathrm{N}_{2(g)}+3 \mathrm{H}_{2(g)}\)	(d) \(2 \mathrm{~N}_{2} \mathrm{O}_{(g)} \stackrel{\Delta}{\longrightarrow} 2 \mathrm{~N}_{2(g)}+\mathrm{O}_{2(g)}\)

3)

Read the passage given below and answer the following questions:
A reaction in which rate of reaction is independent of concentration of the reactants is called zero order reaction. Photochemical combination of hydrogen and chlorine to give hydrogen chloride is an example of zero order reaction. The rate constant of a zero order reaction is equal to the rate of reaction. The half life period of a zero order reaction is directly proportional to initial concentration of the reactant. For a zero order reaction, \(k=\frac{1}{t}\left\{[A]_{0}-[A]\right\}\)
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(c) Assertion is correct statement but reason is wrong statement.

(d) Assertion is wrong statement but reason is correct statement

(i) Assertion : For a zero order reaction, plot of rate vs concentration will be a straight line parallel to concentration axis.
Reason : For a zero order reaction, rate is independent of concentration.
(ii) Assertion : Photochemical combination of hydrogen and chlorine to give hydrogen chloride is an example of zero order reaction.
Reason : The rate of reaction depends on the concentration of hydrogen and independent of concentration of chlorine.
(iii) Assertion : If in a zero order reaction, the concentration of the reactant is doubled, the half-life period is also doubled.
Reason : For a zero order reaction, the rate of reaction is independent of initial concentration
(iv) Assertion : In a reaction A -7 products, the concentration of the reactant is reduced to zero after a finite time.
Reason : The order of reaction is zero.

4)

Read the passage given below and answer the following questions :
Decrease in concentration of reactant or increase in concentration of product per unit time is called rate of reaction. It is of two types:
(i) Instantaneous rate of reaction : Rate of change of concentration of reactant or product at a particular time is called instantaneous rate of reaction.
\(r_{\text {inst. }}=\frac{d C}{d t}\)
where, dC = infinitely small change in concentration
dt = infinitely small change in time.
(ii) Average rate of reaction: Ratio of change in concentration and time required for the change is average rate of reaction.
\(r_{a v}=\frac{\Delta x}{\Delta t}=\frac{\text { Change in concentration }}{\text { Time required for the change }}\)
For a reaction of the type, \(m_{1} A+m_{2} B \rightarrow n_{1} C+n_{2} D\)
Rate of reaction is given as
\(-\frac{1}{m_{1}} \frac{d[A]}{d t}=-\frac{1}{m_{2}} \frac{d[B]}{d t}=+\frac{1}{n_{1}} \frac{d[C]}{d t}=+\frac{1}{n_{2}} \frac{d[D]}{d t}\)
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion

(c) Assertion is correct statement but reason is wrong statement.

(d) Assertion is wrong statement but reason is correct statement.

(i) Assertion : The kinetics of the reaction,\(m A+n B+p C \rightarrow m^{\prime} X+n^{\prime} Y+p^{\prime} Z\) obey the rate expression as \(\frac{d x}{d t}=k[A]^{m}[B]^{n}\) .
Reason : The rate of the reaction does not depend upon the concentration of C.
(ii) Assertion: Instantaneous rate of reaction is equal to dx/ dt.
Reason : It is the rate of reaction at any particular instant of time.
(iii) Assertion : For the reaction,\(R \mathrm{Cl}+\mathrm{NaOH} \rightarrow \mathrm{ROH}+\mathrm{NaCl}\) the rate of reaction is reduced to half on reducing the concentration of RCl to half.
Reason : The sate of reaction is represented by k[RCl].
(iv) Assertion : In rate law, unlike in the expression for equilibrium constants, the exponents for concentrations do not necessarily match the stoichiometric coefficients.
Reason: It is the mechanism and not the balanced chemical equation for the overall change that governs the reaction rate.

5)

Read the passage given below and answer the following questions :
For a first order reaction \(A \rightarrow \text { Products, } k=\frac{2.303}{t} \log \frac{a}{a-x}\) were a is the initial concentration of A and (a-x) is the concentration of A after time t. k is rate constant. Its value is constant at constant temperature for a reaction. The time in which half of the reactant is consumed is called half-life period. Half-life period of a first order reaction is constant. Its value is independent of initial concentration or any other external conditions.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(i) Assertion : Rate of reaction doubles when concentration of reactant is doubled if it is a first order reaction.
Reason : Rate constant also doubles,

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion

(c) Assertion is correct statement but reason is wrong statement

(d) Assertion is wrong statement but reason is correct statement.

(ii) Assertion : Hydrolysis of ethyl acetate in presence of acid is a reaction of first order whereas in presence of alkali, it is a reaction of second order.
Reason : Acid only acts as a catalyst whereas alkali acts as one of the reactants.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion

(c) Assertion is correct statement but reason is wrong statement

(d) Assertion is wrong statement but reason is correct statement.

(iii) Assertion : For a first -order reaction, the concentration of the reactant decreases exponentially with time.
Reason : Rate of reaction at any time depends upon the concentration of the reactant at that time.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion

(c) Assertion is correct statement but reason is wrong statement

(d) Assertion is wrong statement but reason is correct statement.

(iv) Assertion : Half-life period for a first order reaction is independent of initial concentration of the reactant.
Reason : For a first order reaction, \(t_{1 / 2}=\frac{0.693}{k}\), where k is rate constant.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion

(c) Assertion is correct statement but reason is wrong statement

(d) Assertion is wrong statement but reason is correct statement.

CBSE 12th Standard Chemistry Subject Electrochemistry Chapter Case Study Questions 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions :
The potential of each electrode is known as electrode potential. Standard electrode potential is the potential when concentration of each species taking part in electrode reaction is unity and the reaction is taking place at 298 K. By convention, the standard ectrode potential of hydrogen (SHE) is 0.0 V. The electrode potential value for eacfi electrode process is a measure of relative tendency of the active species in the process to remain in the oxidisedlreduced form. The negative electrode potential means that the redox couple is stronger reducing agent than H⁺/H₂ couple. A positive electrode potential means that the redox couple is a weaker reducing agent than the H⁺/H₂ couple. Metals which have higher positive value of standard reduction potential form the oxides of greater thermal stability.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(i) Assertion : An electrochemical cell can be set-up only if the redox reaction is spontaneous.
Reason : A reaction is spontaneous if the free energy change is negative.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion

(c) Assertion is correct statement but reason is wrong statement.

(d) Assertion is wrong statement but reason is correct statement.

(ii) Assertion : The standard electrode potential of hydrogen is 0.0 V.
Reason : It is by convention.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion

(c) Assertion is correct statement but reason is wrong statement.

(d) Assertion is wrong statement but reason is correct statement.

(iii) Assertion : The negative value of standard reduction potential means that reduction takes place on this electrode with reference to hydrogen electrode.
Reason : The standard electrode potential of a half cell has a fixed value.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion

(c) Assertion is correct statement but reason is wrong statement.

(d) Assertion is wrong statement but reason is correct statement.

(iv) Assertion : The absolute value of electrode potential cannot be determined experimentally.
Reason : The electrode potential values are generally determined with respect to SHE.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion

(c) Assertion is correct statement but reason is wrong statement.

(d) Assertion is wrong statement but reason is correct statement.

2)

Read the passage given below and answer the following questions:
Two types of conductors are generally used, metallic and electrolytic. Free electrons are the current carrier in metallic and in electrolytic conductors, free ions. Specific conductance or conductivity of an electrolytic solution is given by
\(\kappa=C \times \frac{l}{A}\)
where, C = l/R and l/A = G* (cell constant)
Molar conductance (\(\Lambda_{m}\)) and equivalent conductance (\(\Lambda_{e}\) ) of an electrolyte solution are calculated as
\(\Lambda_{m}=\frac{\kappa \times 1000}{M} \text { or } \Lambda_{e}=\frac{\kappa \times 1000}{N}\)
where, M = molarity of solution and Nis normality of solution. Molar conductance of strong electrolyte depends on the concentration.
\(\Lambda_{m}=\Lambda_{m}^{0}-b \sqrt{C}\)
\(\Lambda_{m}^{\circ}\) = molar conductance at infinite dilution, b = constant, C = conc of solution
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(i) Assertion : The molar conductivity of strong electrolyte decreases with increase in concentration.
Reason : At high concentration, migration of ions is slow

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(c) Assertion is correct statement but reason is wrong statement

(d) Assertion is wrong statement but reason is correct statement.

(ii) Assertion : Equivalent conductance of all electrolytes increases with increasing concentration.
Reason : More number of ions are available per gram equivalent at higher concentration.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(c) Assertion is correct statement but reason is wrong statement

(d) Assertion is wrong statement but reason is correct statement.

(iii) Assertion : Specific conductance decreases with dilution whereas equivalent conductance increases.
Reason : On dilution, number of ions per milli litre decreases but total number of ions increases considerably

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(c) Assertion is correct statement but reason is wrong statement

(d) Assertion is wrong statement but reason is correct statement.

(iv) Assertion : The ratio of specific conductivity to the observed conductance does not depend upon the concentration of the solution taken in the conductivity cell.
Reason : Specific conductivity decreases with dilution whereas observed conductance increases with dilution.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(c) Assertion is correct statement but reason is wrong statement

(d) Assertion is wrong statement but reason is correct statement.

3)

Read the passage given below and answer the following questions:
Electrical work done in unit time is equal to electrical potential multiplied by total charge passed. In order to obtain maximum work from a cell, the charge has to be passed reversibly. The reversible work done by a cell is equal to decrease in its Gibb's energy. Hence, Gibb's energy of reaction is given by
\(\Delta G=-n F E_{\text {cell }}\)
Hence, E is the emf of the cell and nF is the amount of energy.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices
(i) Assertion : \(\Delta G^{\circ}=-n F E^{\circ}\)
Reason : E^o should be positive for a spontaneous reaction

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(c) Assertion is correct statement but reason is wrong statement.

(d) Assertion is wrong statement but reason is correct statement.

(ii) Assertion : An electrochemical cell can be set up only if the redox reaction is spontaneous.
Reason : A reaction is spontaneous if free energy change is negative.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(c) Assertion is correct statement but reason is wrong statement.

(d) Assertion is wrong statement but reason is correct statement.

(iii) Assertion : Current stops flowing when E_cell = 0.
Reason : Equilibrium of the cell reaction is attained.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(c) Assertion is correct statement but reason is wrong statement.

(d) Assertion is wrong statement but reason is correct statement.

(iv) Assertion: E_cell should have a positive value for the cell to function.
Reason : E_cell= E_cathode - E_anode

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(c) Assertion is correct statement but reason is wrong statement.

(d) Assertion is wrong statement but reason is correct statement.

4)

Read the passage given below and answer the following questions:
Nernst equation relates the reduction potential of an electrochemical reaction to the standard potential and activities of the chemical species undergoing oxidation and reduction. Let us consider the reaction, \(M_{(a q)}^{n+} \longrightarrow n M_{(s)}\)
For this reaction, the electrode potential measured with respect to standard hydrogen electrode can be given as
\(E_{\left(M^{n+} / M\right)}=E_{\left(M^{n+} / M\right)}^{\circ}-\frac{R T}{n F} \ln \frac{[M]}{\left[M^{n+}\right]}\)
In these questions ( i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion

(c) Assertion is correct statement but reason is wrong statement

(d) Assertion is wrong statement but reason is correct statement.

(i) Assertion : For concentration cell, \(\begin{array}{c} \mathrm{Zn}_{(s)}\left|\mathrm{Zn}^{2+}{ }_{(a q)} \| \mathrm{Zn}^{2+}{ }_{(a q)}\right| \mathrm{Zn} \\ \mathrm{C}_{1} \quad \mathrm{C}_{2} \end{array}\)
For spontaneous cell reaction, C₁ < C₂.
Reason : For concentration cell \(E_{\text {cell }}=\frac{R T}{n F} \log \frac{C_{2}}{C_{1}}\)
For spontaneous reaction, \(E_{\text {cell }}=+\mathrm{ve} \Rightarrow C_{2}>C_{1}\)
(ii) Assertion : For the cell reaction, \(\mathrm{Zn}_{(s)}+\mathrm{Cu}_{(a q)}^{2+} \longrightarrow \mathrm{Zn}_{(a q)}^{2+}+\mathrm{Cu}_{(s)}\) voltmeter gives zero reading at equilibrium.
Reason : At the equilibrium, there is no change in concentration of Cu²⁺ and Zn²⁺ ions.
(iii) Assertion : The Nernst equation gives the concentration dependence of emf of the cell.
Reason : In a cell, current flows from cathode to anode
(iv) Assertion : Increase in the concentration of copper half cell in a cell, increases the emf of the cell
Reason : \(E_{\text {cell }}=E_{\text {cell }}^{\circ}+\frac{0.059}{2} \log \frac{\left[\mathrm{Cu}^{2+}\right]}{\left[\mathrm{Zn}^{2+}\right]}\)

CBSE 12th Standard Chemistry Subject Solution Chapter Case Study Questions 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
The solubility of gases increases with increase of pressure. William Henry made a systematic investigation of the solubility of a gas in a liquid. According to Henry's law "the mass of a gas dissolved per unit volume of the solvent at constant temperature is directly proportional to the pressure of the gas in equilibrium with the solution".
Dalton during the same period also concluded independently that the solubility of a gas in a liquid solution depends upon the partial pressure of the gas. If we use the mole fraction of gas in the solution as a measure of its solubility, then Henry's law can be modified as "the partial pressure of the gas in the vapour phase is directly proportional to the mole fraction of the gas in the solution":
(i) Henry's law constant for the solubility of methane in benzene at 298 K is 4.27 X 10⁵ mm Hg. The solubility of methane in benzene at 298 K under 760 mm Hg is

(a) 4.27 x 10^-5	(b) 1.78 x 10^-3
(c) 4.27 X 10^-3	(d) 1.78 x 10^-5

(ii) The partial pressure of ethane over a saturated solution containing 6.56 x 10^-2 g of ethane is 1 bar. If the solution contains 5.00 x 10^-2 g of ethane then what will be the partial pressure (in bar) of the gas?

(a) 0.762

(b) 1.312

(c) 3.81

(d) 5.0

(iii) K_H (K bar) values for Ar_(g), CO_2(g), HCHO_(g)and CH_4(g) are 40.39, l.67, 1.83 x 10^-5 and 0.413 respectively.
Arrange these gases in the order of their increasing solubility.

\(\text {(a) } \mathrm{HCHO}<\mathrm{CH}_{4}<\mathrm{CO}_{2}<\mathrm{Ar}\)	\(\text { (b) } \mathrm{HCHO}<\mathrm{CO}_{2}<\mathrm{CH}_{4}<\mathrm{Ar}\)
\(\text {(c) } \mathrm{Ar}<\mathrm{CO}_{2}<\mathrm{CH}_{4}<\mathrm{HCHO}\)	\(\text { (d) } \mathrm{Ar}<\mathrm{CH}_{4}<\mathrm{CO}_{2}<\mathrm{HCHO}\)

(iv) Which of the following statements is correct

(a) K_H increases with increase of temperature

(b) K_H decreases with increase of temperature

(c) K_H remains constant with increase oftemperature

(d) K_H first increases then decreases, with increase of temperature.

2)
Read the passage given below and answer the following questions:
At the freezing point of a solvent, the solid and the liquid are in equilibrium. Therefore, a solution will freeze when its vapour pressure becomes equal to the vapour pressure of the pure solid solvent.
It has been observed that when a non-volatile solute is added to a solvent, the freezing point of the solution is
always lower than that of the pure solvent. Depression in freezing point can be given as, \(\Delta T_{f}=K_{f} m\)
Where, K_f = Molal freezing point depression constant
or we can write, \(\Delta T_{f}=\frac{K_{f} \times W_{B} \times 1000}{W_{A}^{1} \times M_{B}}\)
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: 0.1 M solution of glucose has same depression in the freezing point as 0.1 M solution of urea.
Reason: K_ffor both has same value.
(ii) Assertion: Larger the value of cryoscopic constant of the solvent, lesser will be the freezing point of the solution.
Reason: Extent of depression in the freezing point depends on the nature of the solvent.
(iii) Assertion: The water pouch of instant cold pack for treating athletic injuries breaks when squeezed and NH₄NO₃ dissolves thus lowering the temperature.
Reason: Addition of non-volatile solute into solvent results into depression of freezing point of solvent.
(iv) Assertion: If a non-volatile solute is mixed in a solution then elevation in boiling point and depression in freezing point both will be same.
Reason: Elevation in boiling point and depression in freezing point both depend on number of particles of solute.
3)
Read the passage given below and answer the following questions:
According to Raoult's law, the partial pressure of two components of the solution may be given as:
\(p_{A}=p_{A}^{\circ} x_{A} \text { and } p_{B}=p_{B}^{\circ} x_{B}\)
For an ideal solution (obeys Raoult's law always)
\(\Delta H_{\operatorname{mix}}=0, \Delta V_{\operatorname{mix}}=0\)
All solutions do not obey Raoult's law over entire range of concentration. These are known as non-ideal solutions.
For non-ideal solutions, \(p_{A} \neq p_{A}^{\circ} x_{A} \text { or } p_{B} \neq p_{B}^{\circ} x_{B}\)
Positive deviation \(\Rightarrow p_{A}>p_{A}^{\circ} x_{A} \text { and } p_{B}>p_{A}^{\circ} x_{B}\)
Negative deviation \(\Rightarrow p_{A}<p_{A}^{\circ} x_{A} \text { and } p_{B}<p_{B}^{\circ} x_{B}\)
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statemeht but reason is correct statement.
(i) Assertion: An ideal solution obeys Raoults law.
Regson : In an ideal solution, solute-solute as well as solvent-solvent interactions are similar to solutesolvent interactions.
(ii) Assertion: Acetone and aniline show negative deviations.
Reason: H-bonding between acetone and aniline is stronger than that between acetone-acetone and aniline-aniline.
(iii) Assertion: The solutions which show negative deviations from Raoult's law are called maximum boiling azeotropes.
Reason: 68% nitric acid and 32% water by mass form maximum boiling azeotrope.
(iv) Assertion: \(\Delta H_{\mathrm{mix}}\) and \(\Delta V_{\operatorname{mix}}\)are positive for an ideal solution.
Reason: The interactions between the particles of the components of an ideal solution are almost identical as between particles in the liquids.
4)
Read the passage given below and answer the following questions:
The phenomenon of the flow of solvent through a semipermeable membrane from pure solvent to the solution is called osmosis.
Sometimes a pressure is applied to stop the process of osmosis, this is known as osmotic pressure. It is denoted by \(\pi \). Osmotic pressure is expressed as: \(\pi \) = CRT
Since, osmotic pressure depends upon the molar concentration of solution, therefore it is a colligative property.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: If red blood cells were removed from the body and placed in pure water, pressure inside the cells increases.
Reason: The concentration of salt content in the cells increases.
(ii) Assertion: When a solution is separated from the pure solvent by a semipermeable membrane, the solvent molecules pass through it from pure solvent side to the solution side.
Reason: Diffusion of solvent occurs from a region of high concentration to a region of low concentration solution.
(iii) Assertion: Two solutions having same osmotic pressure at a given temperature are called isotonic solutions.
Reason: Osmotic pressure is not a colligative property.
(iv) Assertion: The preservation of meat by salting and fruits by adding sugar protects against bacterial action.
Reason: A bacterium on salted meat or candid fruit loses water due to osmosis shrivels and ultimately dies.
5)
Read the, passage given below and answer the following questions:
If some solute is added to a solvent, the boiling point of solution increases. This is known as elevation in boiling point.
\(\Delta T_{b}=K_{b} m\) ,where, K_b = Molal elevation constant
\(\Delta T_{b} \propto m\)
Hence, it is a colligative property.
Also, \(K_{b}=\frac{M R T_{b}^{2}}{\Delta_{\text {vap }} H \times 1000}\)
where, M= Molar mass of solvent
\(\Delta_{\text {vap }} H\) = Enthalpy of vaporisation
Molar mass can also be calculated using elevation in boiling point.
\(M_{B}=\frac{K_{b} \times W_{B} \times 1000}{\Delta T_{b} \times W_{A}}\)
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: In a pressure cooker, the water is brought to boil. The cooker is then removed from the stove. Now on removing the lid of pressure cooker, the water starts boiling again.
Reason: The impurities in water bring down its boiling point.
(ii) Assertion: On dissolving 3.24 g of sulphur in 40 g of benzene, boiling point of solution get higher than that of benzene by 0.081 K, then the formula of sulphur is S₈. (K_b for benzene = 2.53 K kg mol
Reason: Molecular mass of sulphur comes out to be 253.
(iii) Assertion: When sugar is added to water, boiling point of water increases.
Reason: When a non-volatile solute is added to a solvent, elevation in boiling point is observed.
(iv) Assertion: Cooking time in pressure cookers is reduced.
Reason: Boiling point inside the pressure cooker in raised.

CBSE 12th Standard Chemistry Subject The Solid State Chapter Case Study Questions 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
In hexagonal system of crystals, a frequently encountered arrangement of atoms is described as a hexagonal prism. Here, the top and bottom of the cell are regular hexagons and three atoms are sandwiched in between them. A space-filling model of this structure, called hexagonal close packed (hep), is constituted of a sphere on a flat surface surrounded in the same plane by six identical spheres as closely as possible. Three spheres are then placed over the first layer so that they touch each other and represent the second layer. Each one of these three spheres touches three spheres of the bottom layer. Finally, the second layer is covered with a third layer that is identical to the bottom layer in relative position.
The following questions are multiple choice questions. Choose the most appropriate answer:
(I) The number of atoms in this hep unit cell is

(a) 4

(b) 6

(c) 12

(d) 17

(ii) The volume of this hep unit cell is

\(\text { (a) } 24 \sqrt{2} r^{3}\)

\(\text { (b) } 16 \sqrt{2} r^{3}\)

\(\text { (c) } 12 \sqrt{2} r^{3}\)

\(\text { (d) } \frac{64}{3 \sqrt{3}} r^{3}\)

(iii) The empty space in this hep unit cell is

(a) 74%

(b) 47.6%

(c) 32%

(d) 26%

(iv) In hexagonal close packing of spheres in three-dimensions

(a) in one unit cell there are 12 octahedral voids and all are completely inside the unit cell

(b) in one unit cell there are six octahedral voids and all are completely inside the unit cell

(c) in one unit cell there are six octahedral voids out of which three are completely inside the unit cell and other three are from contributions of octahedral voids which are partially inside the unit cell

(d) in one unit cell there are 12 tetrahedral voids, all are completely inside the unit cell.

2)
Read the passage given below and answer the following questions:
Electron microscopic study of crystal defects enables us not only to reveal various structural imperfections, but also to discover their formation, mechanisms and to understand their effects on the properties of solid materials. There are commonly two types of imperfections: electronic imperfections and atomic imperfections or point defects.
Electronic imperfections correspond to defects in ionic crystal due to the electrons. Atomic imperfections or point defects correspond to the irregularity of atoms around a point or an atom. The point defects in ionic crystals may be classified as : defects in stoichiometric crystals, defects in non-stoichiometric crystals and impurity defects.
In stoichiometric crystals, generally two types of defects are observed: Schottky defect and Frankel defect. Schottky defect arises when some of the atoms or ions are missing from their normal lattice sites. Due to the schottky defect, density of ionic crystals decreases markedly. For example NaCI, KCI, CsCI, AgBr ionic solids have schottky defects. It has been observed that in NaCl, there are about 10⁶ Schottky pairs per cm³at room temperature. Frankel defect arises when an ion is missing from its normal position and occupies an interstitial site between the lattice points. It does not affect the density of the crystals.
In non-stoichiometric crystals, two types of defects are there; metal excess defects and metal deficient defects. In metal excess defect, the positive ions are in excess whereas in metal deficient defects, number of positive ions are less than the negative ions. Impurity defects arise due to presence of some impurity ions at the lattice sites.
In these questions (i - iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) As ertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: In any ionic solid [MX] with Schottky defects, the number of positive and negative ions are same.
Reason: Equal number of cation and anion vacancies are present.
(ii) Assertion: Due to Frenkel defect there is no effect on the density of the crystalline solid.
Reason: In Frenkel defect, no cation or anion leaves the crystal.
(iii) Assertion: No compound has both Schottky and Frenkel defects.
Reason: Schottky defects change the density of the solid.
(iv) Assertion: NaCI and KCI show metal excess defect.
Reason: Zinc oxide is white in colour at room temperature and on heating it loses oxygen and turns yellow due to metal excess defect.
3)
Read the passage given below and answer the following questions:
In an assembly of atoms or molecules, a solid phase is formed whenever the interatomic attractive forces significantly exceed the disruptive thermal forces and thus restrict the mobility of atoms, forcing them into more or less fixed positions. From energy considerations, it is evident that in such solids the atoms or molecules will always attempt to assume highly ordered structures which are characterised by symmetry. Depending on the nature of the active interatomic forces, all solids may be subdivided into the following categories:
Ionic solids: These solids consist of positively and negatively charged ions arranged in a regular fashion throughout the solid. These solids are veryhard and brittle, have very high melting points and have high enthalpies of vaporisation, e.g., NaCl, MgO, KCl, LiCl etc.
Covalent solids: In these solids, the constituent particles are atoms which are linked together by a continuous system of covalent bonds. These bonds are strong and directional in nature. The covalent crystals are hard, have high melting points, are poor conductors of electricity. Diamond is a typical example of covalent solids.
Metallic solids : In these solids, the constituent particles are positive ions immersed in a sea of mobile electrons. Metallic solids may be hard as well as soft. They are good conductors of heat and electricity e.g., common metals such as nickel, copper and alloys.
Molecular solids : In these the constituent particles are molecules. The molecules are held together by dispersion forces or London forces, dipole-dipole forces or hydrogen bonds.
In these questions (Q. No. i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Molecular solids are characterized by low melting point.
Reason: Molecular solids are made up of covalent molecules.
(ii) Assertion: Ionic solids are characterized by high melting and boiling point.
Reason: Ionic solids have coulombic forces of attraction between their ions.
(iii) Assertion: Covalent solids are insulators of electricity.
Reason: Covalent solids are constituted by ions.
(iv) Assertion: Diamond and graphite do not have the same covalent structure.
Reason: Silicon carbide is typical example of network solid.
4)
Read the passage given below and answer the following questions:
Most important crystal lattices are the simple cubic, body centred cubic and face centred cubic. In simple cubic lattice, all the atoms are present at all the corners of the cube. In body-centred cubic lattice, atoms are present at all the corners and at the body-centre. In face-centred cubic lattice, atoms are present at the corners and at the centers of all' six faces.
In the formation of crystals, the constituent particles get closely packed together. The closely packed arrangement is that in which maximum available space is occupied leaving minimum vacant space. The most efficient close packing, can be achieved in two ways, one which is called hexagonal close packing (hcp) and the other, cubic close packing (ccp or fcc).
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Face centred cubic cell has 4 atoms per unit cell.
Reason: In fcc unit cell, there are 8 atoms at the corners and 6 atoms at face centres.
(ii) Assertion: fee and hep have same packing efficiency.
Reason: bee and fee both have same number of atoms per unit cell and same arrangement.
(iii) Assertion: The total number of atoms present in a simple cubic unit cell is one.
Reason: Simple cubic unit cell has atoms at its corners, each of which is shared between eight adjacent unit cells.
(iv) Assertion: The packing efficiency is maximum for the fccstructure.
Reason: The coordination number is 12 in fcc structures.

CBSE 12th Standard Chemistry Subject Biomolecules Chapter Case Study Questions With Solution 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
Pentose and hexose undergo intramolecular hemiacetal or hemiketal formation due to combination of the -OH group with the carbonyl group. The actual structure is either of five or six membered ring containing an oxygen atom. In the free state all pentoses and hexoses exist in pyranose form (resembling pyran). However, in the combined state some of them exist as five membered cyclic structures, called furanose (resembling furan).

The cyclic structure of glucose is represented by Haworth structure:

\(\alpha \) and \(\beta\) -D-glucose have different configuration at anomeric (C-l) carbon atom, hence are called anomers and the C-l carbon atom is called anomeric carbon (glycosidic carbon).
The six membered cyclic structure of glucose is called pyranose structure.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) \(\alpha\) -D(+)-glucose and \(\beta\) -D( +)glucose are

(a) enantiomers

(b) conformers

(c) epimers

(d) anomers

(ii) The following carbohydrate is

(a) a ketohexose	(b) an aldohexose
(c) an \(\alpha \)-furanose	(d) an \(\alpha \)-pyranose

(iii) In the following structure,

anomeric carbon is

(a) C-l

(b) C-2

(c) C-3

(d) C-4

(iv) The term anomers of glucose refers to

(a) isomers of glucose that differ in configurations at carbons one and four (C-l and C-4)

(b) a mixture of (D)-glucose and (L)-glucose

(c) enantiomers of glucose

(d) isomers of glucose that differ in configuration at carbon one (C-l).

2)

Read the passage given below and answer the following questions:
When a solution of an \(\alpha \) -amino acid is placed in an electric field depending on the pH of the medium, following three cases may happen.

(i) In alkaline solution,\(\alpha \) -amino acids exist as anion II, and there is a net migration of amino acid towards the anode.
(ii) In acidic solution, \(\alpha \) -amino acids exist as cation III, and there is a net migration of amino acid towards the cathode.
(iii) If II and III are exactly balanced there is no net migration; under such conditions anyone molecule exists as a positive ion and as a negative ion for exactly the same amount of time, and any small movement in the direction of one electrode is subsequently cancelled by an equal movement back toward the other electrode. The pH of the solution in which a particular amino acid does not migrate under the influence of an electric field is called the isoelectric point of that amino acid.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i)
Arrange in order of increasing acid strengths.

(a) X>Z>Y

(b) Z

(c) X>Y>Z

(d) Z>X>Y

(ii) In aqueous solutions, amino acids mostly exist as

\(\text { (a) } \mathrm{NH}_{2}-\mathrm{CH} R-\mathrm{COOH}\)	\(\text { (b) } \mathrm{NH}_{2}-\mathrm{CH} R-\mathrm{COO}^{-}\)
\(\text { (c) } \mathrm{NH}_{3} \mathrm{CH} R \mathrm{COOH}\)	\(\text { (d) } \mathrm{H}_{3} \mathrm{NCH} R \mathrm{COO}^{-}\)

(iii) Amino acids are least soluble

(a) at pH 1	(b) at pH 7
(c) at their isoelectric points	(d) none of these.

(iv) The \(pK_{a_{1}}\)and \(pK_{a_{2}}\) of an amino acid are 2.3 and 9.7 respectively. The isoelectric point of the amino acid is

(a) 12.0

(b) 7.4

(c) 6.0

(d) 3.7

3)

Read the passage given below and answer the following questions:
Carbohydrates can exist in either of two conformations, as determined by the orientation of the hydroxyl group about the asymmetric carbon farthest from the carbonyl.

By convention, a monosaccharide is said to have D-configuration if the hydroxyl group attached to the asymmetric carbon atom adjacent to the - CH₂OH group is on the right hand side irrespective of the positions of the other hydroxyl groups. On the other hand, the molecule is assigned L-configuration if the - OH group attached to the carbon adjacent to the - CH₂OH group is on the left hand side.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) D-Glyceraldehyde and L-Glyc~raldehyde are

(a) epimers	(b) enantiomers
(c) anomers	(d) conformational diasteriomers

(ii) Which of the following monosaccharides, is the majority found in the human body?

(a) D-type

(b) L-type

(c) Both of these

(d) None of these

(iii) Monosaccharides contain

(a) always six carbon atoms	(b) always five carbon atoms
(c) always four carbon atoms	(d) may contain 3 to 7 carbon atoms

(iv) The correct corresponding order of names of four aldoses with configuration given below

respectively, is

(a) L-erythrose, L-threose, L-erythrose, D-threose

(b) D-threose, D-erythrose, L-tl?repse, L-erythrose

(c) L-erythrose, L-threose, D-erythrose, D-threose

(d) D-erythrose, D-threose, L-erythrose, L-threose.

4)

Read the passage given below and answer the following questions:
Carbohydrates are polyhydroxy aldehydes and ketones and those compounds which on hydrolysis give such compounds are also carbohydrates. The carbohydrates which are not hydrolysed are called monosaccharides. Monosaccharides with aldehydic group are called aldose and those which free ketonic groups are called ketose. Carbohydrates are optically active. Number of optical isomers = 2ⁿ
Where n = number of asymmetric carbons. Carbohydrates are mainly synthesised by plants during photosynthesis.
The monosaccharides give the characteristic reactions of alcohols and carbonyl group (aldehydes and ketones). It has been found that these monosaccharides exist in the form of cyclic structures. In cyclization, the -OH groups (generally C₅ or C₄ in aldohexoses and C₅ or C₆ in ketohexoses) combine with the aldehyde or keto group. As a result, cyclic structures of five or six membered rings containing one oxygen atom are formed, e.g., glucose forms a ring structure. Glucose contains one aldehyde group, one 1^o alcoholic group and four 2^o alcoholic groups in its open chain structure.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) First member of ketos sugar is

(a) ketotriose

(b) ketotetrose

(c) ketopentose

(d) ketohexose

(ii) In CH₂OHCHOHCHOHCHOHCHOHCHO, the number of optical isomers will be

(a) 16

(b) 8

(c) 32

(d) 4

(iii) Some statements are given below:
1. Glucose is aldohexose.
2. Naturally occurring glucose is dextrorotatory.
3. Glucose contains three, chiral centres.
4. Glucose contains one 1^o alcoholic group and four 2^o alcoholic groups.
Among the above, correct statements are

(a) 1 and 2 only	(b) 3 and 4 only
(c) 1,2 and 4 only	(d) 1,2,3 and 4

(iv) Which of the following reactions of glucose can be explained only by its cyclic structure?

(a) Glucose forms cyanohydrin with HCN

(b) Glucose reacts with hydroxylamine to form an oxime

(c) Pentaacetate of glucose does not react with hydroxylamine

(d) Glucose is oxidised by nitric acid to gluconic acid .

CBSE 12th Standard Chemistry Subject Amines Chapter Case Study Questions With Solution 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
When the mixture contains the three amine salts (1°, 2° and 3°) along with quaternary salt, it is distilled with KOH solution. The three amines distill, leaving the quaternary salt unchanged in the solution. Then the mixture of amines is separated by fractional distillation, Hinsbergs method and Hoffmann's method.

The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Hinsberg reagent is

(a) aliphatic sulphonyl chloride	(b) phthalamide
(c) aromatic sulphonyl chloride	(d) anhydrous ZnCl₂ + conc. HCl.

(ii) Primary amine with Hinsberg's reagent forms

(a) N-alkyl benzene sulphonamide soluble in KOH solution

(b) N-alkyl benzene sulphonamide insoluble in KOH solution

(c) N, N-dialkyl benzene sulphonamide soluble in KOH solution

(d) N, N-dialkyl benzene sulphonamide insoluble in KOH solution.

(iii) To separate amines in a mixture Hoffmann's method is used. The Hoffmann's reagent is

(a) benzenesulphonyl chloride	(b) diethyloxalate
(c) benzeneisocyanide	(d) p-toulenesulphonic acid.

(iv) 3^o amines with Hinsberg's reagent give

(a) no reaction	(b) product which is same as that of 1⁰ amine
(c) product which is same as that of 2° amine	(d) products which is a quaternary salt.

2)

Read the passage given below and answer the following questions:
A mixture of two aromatic compounds (A) and (B) was separated by dissolving in chloroform followed by extraction with aqueous KOH solution. The organic layer containing compound (A), when heated with alcoholic solution of KOH produce C₇H₅N (C) associated with unpleasant odour.
The following questions are multiple choice questions. Choose the most appropriate answer:
The reaction of (A) with alcoholic solution of KOH to produce (C) of unpleasant odour is called

(a) Sandmeyer reaction	(b) Carbylamine reaction
(c) Ullmann reaction	(d) Reimer-Tiemann reaction

(ii) The alkaline aqueous layer (B) when heated with chloroform and then acidified give a mixture of isomeric compounds of molecular formula C₇H₆O₂. (B) is

(a) C₆H₅CHO

(b) C₆H₅COOH

(c) C₆H₅CH3

(d) C₆H₅OH

(iii) In the chemical reaction, \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{NH}_{2}+\mathrm{CHCl}_{3}+3 \mathrm{KOH} \longrightarrow(A)+(B)+3 \mathrm{H}_{2} \mathrm{O},\) the compounds (A) and (B) are respectively

(a) C₂H₅NC and KCI	(b) C₂H₅CN and KCI
(c) CH₃CH₂CONH₂ and KCI	(d) C₂H₅NC and K₂CO₃

(iv) Direct nitration of an aromatic compound (A) is not feasible because

(a) the reaction cannot be stopped at the mononitration stage

(b) a mixture of o, m and p-nitroaniline is always obtained

(c) nitric acid oxidises most of the aromatic compound to give oxidation products along with only a small amount of nitrated products

(d) all of the above

3)
Read the passage given below and answer the following questions:
The amines are basic in nature due to the presence of a lone pair of electron on N-atom of the -NH2 group, which it can donate to electron deficient compounds. Aliphatic amines are stronger bases than NH₃ because of the +1 effect of the alkyl groups. Greater the number of alkyl groups attached to N-atom, higher is the electron density on it and more will be the basicity. Thus, the order of basic nature of amines is expected to be 3° > 2° > 1°, however the observed order is 2° > 1° > 3°. This is explained on the basis of crowding on N-atom of the amine by alkyl groups which hinders the approach and bonding by a proton, consequently, the electron pair which is present on N is unavailable for donation and hence 3° amines are the weakest bases. Aromatic amines are weaker bases than ammonia and aliphatic amines. Electron -donating groups such as -CH₃ , -OCH₃ , etc. increase the basicity while electron-withdrawing substitutes such as -NO₂ , -CN, halogens, etc. decrease the basicity of amines. The effect of these substituents is more at p than at m-positions.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Which one of the following is the strongest base in aqueous solution?

(a) Methyl amine (b) Trimethyl amine (c) Aniline (d) Dimethyl amine

(ii) Which order of basicity is correct?

(a) Aniline> m-toluidine > o-toluidine (b) Aniline> o-toluidine > m-toluidine (c) o-toluidine> aniline> m-toluidine (d) o-toluidine < aniline < m-toluidine

(iii) What ts the decreasing order of basicity of primary, secondary and tertiary ethylamines and NH₃?

(a) NH₃ > C₂H₅NH₂ > (C₂H₅)₂NH > (C₂H₅)₃N (b) (C₂H₅)₃N> (C₂H₅)₂NH > C₂H₅NH₂ > NH₃

(c) (C₂H₅)₂NH >C₂H₅NH₂ > (C₂H₅)₃N > NH₃ (d) (C₂H₅)₂NH> (C₂H₅)₃N > C₂H₅NH₂ > NH₃

(iv) Choose the correct statement.

(a) Methylamine is slightly acidic. (b) Methylamine is less basic than ammonia. (c) Methylamine is a stronger base than ammonia. (d) Methylamine forms salts with alkalie
4)
Read the passage given below and answer the following questions:
Amines are alkyl or aryl derivatives of ammonia formed by replacement of one or more hydrogen atoms. Alkyl derivatives are called aliphatic amines and aryl derivatives are known as aromatic amines. The presence of aromatic amines can be identified by performing dye test. Aniline is the simplest example of aromatic amine. It undergoes electrophilic substitution reactions in which - NH₂ group strongly activates the aromatic ring through delocalisation oflone pair of electrons of N-atom. Aniline undergoes electrophilic substitution reactions. Ortho and para positions to the -NH₂ group become centres of high electrons density. Thus, -NH₂ group is ortho and para-directing and powerful activating group. The following questions are multiple choice questions.
Choose the most appropriate answer:
(i) Cyclohexylamine and aniline can be distinguished by

(a) Hinsberg test (b) carbylamine test (c) Lassaigne test (d) azo dye test

(ii) Which of the following compounds gives-dye test?

(a) Aniline (b) Methyl amine (c) Diphenyl amine (d) Ethyl amine

(iii) Oxidation of aniline with manganese dioxide and sulphuric acid produces

(a) phenylhydroxylamine (b) nitrobenzene (c) p-benzoquinone (d) phenol.

(iv) Aniline when treated with conc, HNO₃ and H₂SO₄ gives

(a) phenylhydroxylamine (b) m-nitroaniline (c) p-benzoquinone (d) nitrobenzene.

CBSE 12th Standard Chemistry Subject Aldehydes , Ketones and Carboxylic Acids Chapter Case Study Questions With Solution 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)
Read the passage given below and answer the following questions:
The addition reaction of enol or enolate to the carbonyl functional group of aldehyde or ketone is known as aldol addition. The \(\beta\)-hydroxyaldehyde or \(\beta\)-hydroxyketone so obtained undergo dehydration in second step to produce a conjugated enone. The first part of reaction is an addition reaction and the second part is an elimination reaction. Carbonyl compound having \(\alpha\)-hydrogen undergoes aldol condensation reaction.

The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Condensation reaction is the reverse of which of the following reaction?

(a) Lock and key hypothesis (b) Oxidation

(c) Hydrolysis (d) Glycogen formation

(ii) Which of the following compounds would be the main product of an aldol condensation of acetaldehyde and acetone?

(a) CH₃CH=CHCHO (b) CH₃CH=CHCOCH₃

(c) (CH₃)₂C=CHCHO (d) (CH₃)₂C=CHCOCH₃

(ii) Which combination of carbonyl compounds gives phenyl vinyl ketone by an aldol condensation?

(a) Acetophenone and Formaldehyde (b) Acetophenone and acetaldehyde

(c) Benzaldehyde and acetaldehyde (d) Benzaldehyde and acetone

(iv) Which of the following will undergo aldol condensation?

(a) HCHO (b) CH₃CH₂OH

(c) C₆H₅CHO (d) CH₃CH₂CHO
2)
Read the passage given below and answer the following questions :
When an aldehyde with no a-hydrogen reacts with concentrated aqueous NaOH, half the aldehyde is converted to carboxylic acid salt and other half is converted to an alcohol. In other words, half of the reactant is oxidized
and other half is reduced. This reaction is known as Cannizzaro reaction

The following questions are multiple choice questions. Choose the most appropriate answer :
(i) A mixture of benzaldehyde and formaldehyde on heating with aqueous NaOH solution gives

(a) benzyl alcohol and sodium formate (b) sodium benzoate and methyl alcohol

(c) sodium benzoate and sodium formate (d) benzyl alcohol and methyl alcohol.

(ii) Which of the following compounds will undergo Cannizzaro reaction?

(a) CH₃CHO (b) CH₃COCH₃

(c) C₆H₅CHO (d) C₆H₅CH₂CHO

(iii) Trichloroacetaldehyde is subjected to Cannizzaro's reaction by using NaOH. The mixture of the products contains sodium trichloroacetate ion and another compound. The other compounds is

(a) 2, 2, 2-trichloroethanol (b) trichloromethanol

(c) 2, 2, 2-trichloropropanol (d) chloroform

(iv) Which of the following reaction will not result in the formation of carbon-carbon bonds?

(a) Cannizzaro reaction (b) Wurtz reaction

(c) Reimer- Tiemann reaction (d) Friedel-Crafts acylation

3)

Read the passage given below and answer the following questions
A tertiary alcohol H upon acid catalysed dehydration gives a product I. Ozonolysis of I leads to compounds J and K. Compound J upon reaction with KOH gives benzyl alcohol and a compound L, whereas K on reaction with KOH gives only M.

The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Compound H is formed by the reaction of

(ii) The structures of compound J, Kand L, respectively, are

(a) PhCOCH₃ , PhCH₂COCH₃ and PhCH₂COO^-K⁺	(b) PhCHO, PhCH₂CHO and PhCOO^-K⁺
(c) PhCOCH₃, PhCH₂CHO and CH3 COO^-K⁺	(d) PhCHO, PhCOCH₃ and PhCOO^-K⁺

(iii) When (J) is treated with acetic anhydride, in the presence of corresponding salt of an acid, the product obtained is

(a) cinnamic acid

(b) crotonic acid

(c) maleic acid

(d) benzylic acida

(iv) Which of the following statements is correct for compound (K)?

(a) It reacts with alkaline KMnO₄ followed by acidic hydrolysis and forms benzoic acid.

(b) It reacts with iodine and NaOH to form triiodomethane.

(c) It is prepared by the reaction of benzene with benzoyl chloride in presence of anhydrous aluminium chloride

(d) It reacts with freshly prepared ammoniacal silver nitrate solution

4)

Read the passage given below and answer the following questions :
Carboxylic acids dissociate in water to give carboxylate ion and hydronium ion.
RCOOH + H₂O \(\longrightarrow\) RCOO^- + H3O⁺
The acidity of carboxyl group is due to the presence of positive charge on oxygen which liberates proton. The carboxylate ion formed is resonance stabilised.

Carboxylic acids are stronger acids than phenols. Electron withdrawing groups (EWG) increase the acidity of carboxylic acids by stabilising the conjugate base through delocalisation of negative charge by inductive and/ or resonance effects. Electron donating group (EDG) decrease the acidity by destabilising the conjugate base.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Which of the following reactions is showing the acidic property of carboxylic acid?

(ii) Which one of the following is the correct order of acidic strength?

(a) CF₃COOH > CHCl₂COOH > HCOOH > C₆H₅CH₂COOH > CH₃COOH

(b) CH₃COOH > HCOOH > CF₃COOH > CHCl₂COOH > C₆H₅CH₂COOH

(c) HCOOH > C₆H₅CH₂COOH > CF₃COOH > CHCl₂COOH > CH₃COOH

(d) CF₃COOH > CH₃COOH > HCOOH > CHCl₂COOH > C₆H₅CH₂COOH

(iii) Which of the following acids has the smallest dissociation constant?

(a) CH₃CHFCOOH	(b) FCH₂CH₂COOH
(c) BrCH₂CH₂COOH	(d) CH₃CHBrCOOH

(iv) The correct order of acidity for the following compounds is

(a) I > II > III > IV	(b) III > I > II > IV
(c) III> IV > II> I	(d) I > III > IV > II

5)
Read the passage given below and answer the following questions:
Aldehydes and ketones having acetyl group are oxidised by sodium hypohalate (NaOX) or halogen and alkali (X₂ + OH^-) to corresponding sodium salt having one carbon atoms less than the carbonyl compound and give a haloform.

Sodium hypoiodite (NaOI) when treated with compounds containing CH₃CO - group gives yellow precipitate of iodoform. Haloform reaction does not affect a carbon-carbon double bond present in the compound.
The following questions are multiple choice questions. Choose the most appropriate answer:

(a) Isopropyl alcohol (b) Propionaldehyde

(c) Ethylphenyl ketone (d) Benzyl alcohol

(ii) Which of the following compounds is not formed in iodoform reaction of acetone?

(a) CH₃COCH₂I (b) ICH₂COCH₂I

(c) CH₃COCHI₂ (d) CH₃COCI₃

(iii) For the given set of reactions

starting compound A corresponds to

(iv) An organic compound 'A' has the molecular formula C₃H₆O. It undergoes iodoform test. When saturated with HCI it gives 'B' of molecular formula C₉H₁₄O. 'A' and 'B' respectively are

(a) propanal and mesityl oxide (b) propanone and mesityl oxide

(c) propanone and 2,6-dimethyl-2,5-hepta-dien-4-one (d) propanone and propionaldehyde

CBSE 12th Standard Chemistry Subject Alcohols , Phenols and Ethers Chapter Case Study Questions With Solution 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
Although chlorobenzene is inert to nucleophilic substitution, however it gives quantitative yield of phenol when heated with aq. NaOH at high temperature and under high pressure. As far as electrophilic substitution in phenol is concerned the - OH group is an activating group, hence, its presence enhances the electrophilic substitution at o- and p-positions.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Conversion of chlorobenzene into phenol involves

(a) modified S_N1 mechanism	(b) modified S_N2 mechanism
(c) both (a) and (b)	(d) elimination-addition mechanism.

(ii) Phenol undergoes electrophilic substitution more readily than benzene because

(a) the intermediate carbo cation is a resonance hybrid of more resonating structures than that from benzene

(b) the intermediate is more stable as it has positive charge on oxygen, which can be better accommodated than on carbon

(c) in one of the canonical structures, every atom (except hydrogen) has complete octet

(d) the -OH group is o, p-directing which like all other o, p-directing group, is activating.

(iii) Phenol on treatment with excess of conc. HNO₃ gives

(a) o-nitrophenol	(b) p-nitrophenol
(c) o-and p-nitrophenol	(d) 2, 4, 6-trinitrophenol

(iv) The major product of the following reaction is

2)
Read the passage given below and answer the following questions:
A compound (X) containing C, Hand O is unreactive towards sodium. It also does not react with Schiff's reagent. On refluxing with an excess ofhydroiodic acid, (X) yields only one organic product (Y). On hydrolysis, (Y) yields a new compound (Z) which can be converted into (Y) by reaction with red phosphorus and iodine. The compound (Z) on oxidation with potassium permanganate gives a carboxylic acid. The equivalent weight of this acid is 60.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The compound (X) is an

(a) acid (b) aldehyde (c) alcohol (d) ether

(ii) The IUPAC name of the acid formed is

(a) methanoic acid (b) ethanoic acid (c) propanoic acid (d) butanoic acid.

(iii) Compound (Y) is

(a) ethyl iodide (b) methyl iodide (c) propyl iodide (d) mixture of (a) and (b).

(iv) Compound (X) on treatment with excess of Cl₂ in presence of light gives

(a) \(\alpha\) - chlorodiethyl ether (b) \(\alpha\), \(\alpha\)' -dichlorodiethyl ether (c) perchlorodiethyl ether (d) none of these.
3)
Read the passage given below and answer the following questions:
Both alcohols and phenols are acidic in nature, but phenols are more acidic than alcohols. Acidic strength of alcohols mainly depends upon the inductive effect. Acidic strength of phenols depends upon a combination of both inductive effect and resonance effects of the substituent and its position on the benzene ring. Electron withdrawing groups increases the acidic strength of phenols whereas electron donating groups decreases the acidic strength of phenols. Phenol is a weaker acid than carboxylic acid.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Phenols are highly acidic as compare to alcohols due to

(a) the higher molecular mass of phenols (b) the stronger hydrogen bonds in phenols

(c) alkoxide ion is a strong conjugate base (d) phenoxide ion is resonance stabilised.

(ii) The correct decreasing order of pK_a value is

(a) II > IV > I > III (b) IV > II > III > I (c) III > II > IV > I (d) IV > I > II > III

(iii) The compound that does not liberate CO₂, on treatment with aqueous sodium bicarbonate solution is

(a) benzoic acid (b) benzenesulphonic acid (c) salicylic acid (d) carbolic acid.

(iv) Most acidic amongst the following is

4)

Read the passage given below and answer the following questions:
Ethers are readily cleaved by HI or HBr at 373 K to form an alcohol and an alkyl halide.
\(R-\mathrm{O}-R+\mathrm{HX} \stackrel{373 \mathrm{~K}}{\longrightarrow} R-X+R-\mathrm{OH}\)
\(R-\mathrm{OH}+\mathrm{HX} \stackrel{373 \mathrm{~K}}{\longrightarrow} R-X+\mathrm{H}_{2} \mathrm{O}\)
Mixed ether, containing primary or secondary alkyl group, when heated with hydrogen halide, the lower alkyl group forms halide and higher will form an alcohol. Tertiary alkyl ether when heated with hydrogen halide gives tertiary alkyl halide.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Among the following ethers, which one will produce methyl alcohol on treatment with hot concentrated HI?


(c) CH₃-CH₂-CH₂-CH₂-O-CH₃

(ii) When CH₂=CH-O-CH₂-CH₃ reacts with one mole of HI, one of the products formed is

(a) ethane

(b) ethanol

(c) iodoethene

(d) ethanal

(iii) (CH₃)₃COCH₃ and CH₃OC₂H₅ are treated with hydroiodic acid. The fragments obtained after reactions are respectively

(a) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CI}+\mathrm{CH}_{3} \mathrm{OH} ; \mathrm{CH}_{3} \mathrm{I}+\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\)	(b) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{CI}+\mathrm{CH}_{3} \mathrm{OH} ; \mathrm{CH}_{3} \mathrm{OH}+\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{I}\)
(c) \(\left(\mathrm{CH}_{3}\right)_{3} \mathrm{COH}+\mathrm{CH}_{3} \mathrm{I} ; \mathrm{CH}_{3} \mathrm{OH}+\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{I}\)	(d) \(\mathrm{CH}_{3} \mathrm{I}+\left(\mathrm{CH}_{3}\right)_{3} \mathrm{COH} ; \mathrm{CH}_{3} \mathrm{I}+\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}\)

(iv) Which of the following ether is unlikely to be cleaved by hot conc. HBr?

5)
Read the passage given below and answer the following questions:
An organic compound (A) having molecular formula C₆H₆O gives a characteristic colour with aqueous FeCl₃ solution. (A) on treatment with CO₂ and NaOH at 400 K under pressure gives (B), which on acidification gives a compound (C). The compound (C) reacts with acetyl chloride to give (D) which is a popular pain killer.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Compound (A) is

(a) 2-hexanol (b) dimethyl ether (c) phenol (d) 2-methyl pentanol.

(ii) Number of carbon atoms in compound (D) is

(a) 7 (b) 6 (c) 8 (d) 9

(iii) The conversion of compound (A) to (C) is known as

(a) Reimer- Tiemann reaction (b) Kolbe's reaction (c) Schimdt reaction (d) Swarts reaction

(iv) Compound (A) on heating with compound (C) in presence of POCl₃ gives a compound (D) which is used

(a) in perfumery as a flavouring agent (b) as an antipyretic (c) as an analgesic (d) as an intestinal antiseptic.

CBSE 12th Standard Chemistry Subject Haloalkanes and Haloarenes Chapter Case Study Questions With Solution 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)
Read the passage given below and answer the following questions:
A primary alkyl halide (A) C₄H₉Br reacted with alcoholic KOH to give compound (B). Compound (B) is reacted with HBr to give compound (C) which is an isomer of (A). When (A) reacted with sodium metal, it gave a compound (D) C₈H₁₈that is different than the compound obtained when n-butyl bromide reacted with sodium metal
The following questions are multiple choice questions. Choose the most ap appropriate answer:
(i) Compound (A) is

(a) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}\) (b)

(c) (d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}\)

(ii) Which type of isomerism is present in compound (A) and (C)?

(a) Positional (b) Functional (c) Chain (d) Both (a) and (c)

(iii) IUPAC name of compound (D) is

(a) n-octane (b) 2,5-dimethylhexane (c) 2-methylheptane (d) 3,4-dimethyl hexane.

(iv) When compoound (C) is treated with alc. KOH and then treated with HBr in presence of peroxide, the compound obtained is

a) (b)

(c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}\) (d)

2)

Read the passage given below and answer the following questions:
Nucleophilic substitution reactions are of two types; substitution nucleophilic bimolecular (S_N2) and substitution nucleophilic unimolecular (S_N1) depending on molecules taking part in determining the rate of reaction. Reactivity of alkyl halide towards S_N1 and S_N2 reactions depends on various factors such as steric hindrance, stability of intermediate or transition state and polarity of solvent. S_N2 reaction mechanism is favoured mostly by primary alkyl halide then secondary and then tertiary. This order is reversed in case of S_N1 reactions.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Which of the following is most reactive towards nucleophilic substitution reaction?

(a) \(\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{Cl}\)

(b) \(\mathrm{CH}_{2}=\mathrm{CHCl}\)

(c) \(\mathrm{ClCH}_{2} \mathrm{CH}=\mathrm{CH}_{2}\)

(d) \(\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CHCl}\)

(ii) Isopropyl chloride undergoes hydrolysis by

(a) S_N1mechanism

(b) S_N2mechanism

(c) S_N1 and S_N2mechanism

(d) neither S_N1 and S_N2mechanism

(iii) The most reactive nucleophile among the following is

(a) CH₃O^-

(b) C₆H₅O^-

(c) (CH₃)₂CHO^-

(d) (CH₃)₃CO^-

(iv) Tertiary alkyl halides are practically inert to substitution by S_N2mechanism because of

(a) insolubility

(b) instability

(c) inductive effect

(d) stearic hindrance.

3)
Read the passage given below and a.9swer the following questions:
A chlorocompound (A) on reduction with Zn-Cu and ethanol gives the hydrocarbon (B) with five carbon atoms. When (A) is dissolved in dry ether and treated with sodium metal it gave 2,2,5,5 tetramethylhexane. The treatment of (A) with alcoholic KCN gives compound (C).
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The compound (A) is

(a) 1-chloro- 2, 2-dimethylpropane (b) 1-chloro- 2, 2-dimethyl butane

(c) 1-chloro-2-methyl butane (d) 2-chloro-2-methyl butane.

(ii) The reaction of (C) with Na, C₂H₅OH gives

(a) (CH₃)₃C CH₂CONH₂ (b) (CH₃)₃C NH₂

(c) (CH)₃C CH₂CH₂NH₂ (d) (CH₃)₂CHCH₂NH₂

(iii) The reaction of (C) with Na, C₂H₅OH is called

(a) Gilman reaction (b) Mendius reaction

(c) Grooves process (d) Swart's reaction.

(iv) Compound (B) is

(a) n-pentane (b) 2, 2-dimethylpropane

(c) 2-methylbutane (d) none of these.

4)

Read the passage given below and answer the following questions:
When haloalkanes with \(\beta\)-hydrogen atom are boiled with alcoholic solution of KOH, they undergo elimination of hydrogen halide resulting in the formation of alkenes. These reactions are called \(\beta\)-elimination reactions or dehydrohalogenation reactions. These reactions follow Saytzeff's rule. Substitution and elimination reactions often compete with each other. Mostly bases behave as nucleophiles and therefore can engage in substitution or elimination reactions depending upon the alkyl halide and the reaction conditions.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Among the following the most reactive towards alcoholic KOH is

(a) \(\mathrm{CH}_{2}=\mathrm{CHBr}\)

(b) \(\mathrm{CH}_{3} \mathrm{COCH}_{2} \mathrm{CH}_{2} \mathrm{Br}\)

(c) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{Br}\)

(d) \(\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{Br}\)

(ii) The general reaction, \(R-X \stackrel{\text { aq. } \mathrm{OH}^{-}}{\longrightarrow} R \mathrm{OH}+X^{-}\) is expected to follow decreasing order of reactivity as in (t- Bu = tertiary Butyl group)

(a) t-BuI> t-BuBr > t-BuCI > t-BuF	(b) t-BuF> t-BuCI > t-BuBr > t-BuI
(c) t-Bu'Br> t-BuCI > t-BuI > t-BuF	(d) t-BuF> t-BuCI > t-BuI > t-BuBr

(iii) Reaction of t-butyl bromide with sodium methoxide produces

(a) sodium t-butoxide	(b) t-butyl methyl ether
(c) iso-butane	(d) iso-butylene.

(iv) In the elimination reactions, the reactivity of alkyl halides follows the sequence

(a) R - F > R - Cl > R - Br > R - I	(b) R - I > R - Br > R - Cl > R - F
(c) R - I > R - F > R - Br > R - Cl	(d) R - F > R-I > R-Br > R-CI

5)
Read the passage given below and answer the following questions:
Consider the given sequence of reactions:
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Identify w.

(ii) When X reacts with CH₃COCI in presence of anhy. AICI₃, the reaction is known as

(a) Fittig reaction (b) Ullmann reaction (c) Wurtz-Fittig reaction (d) Friedel-Crafts acylation reaction.

(iii) When X is treated Ni-Al / NaOH the product obtained is

(a) benzene (b) phenol (c) p-chlorophenol (d) triphenyl.

(iv) Compound Z is

(a) phenol (b) p-chlorophenol (c) p-nitrophenol (d) nitrobenzene

CBSE 12th Standard Chemistry Subject Coordination Compounds Chapter Case Study Questions With Solution 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
The molecular compounds which are formed from the combination of two or more simple stable compounds and retain their identity in the solid as well as in the dissolved state are called coordination compounds. Their properties are completely different from the constituents. In coordination compounds, the central metal atom or ion is linked to a number of ions or neutral molecules, called ligands, by coordinate bonds. For example, Dimethyl glyoxime (dmg) is a bidendate ligand chelating large amounts of metals. When dimethyl glyoxime is added to alcoholic solution of NiCl₂and ammonium hydroxide is slowly added to it, a rosy red precipitate of a complex is formed.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The structure of the complex is

(ii) Oxidation number of Ni in the given complex is

(a) +3

(b) +1

(c) +2

(d) zero.

(iii) Which of the following is true about this complex?

(a) It is paramagnetic, containing 2 unpaired electrons.

(b) It is paramagnetic, containing 1 unpaired electron.

(c) It is paramagnetic, containing 4 unpaired electrons.

(d) It is diamagnetic with no unpaired electron

(iv) Which one will give test for Fe³⁺ ions in the solution?

(a) [Fe(CN)₆]^3-	(b) [Fe(CN)₆]^2-
(c) (NH₄)₂SO₄· FeSO₄· 6H₂O	(d) Fe₂(SO₄)₃

2)

Read the passage given below and answer the following questions:
Coordination compounds are formulated and named according to the IUPAC system.
Few rules for naming coordination compounds are:
(I) In ionic complex, the cation is named first and then the anion.
(II) In the coordination entity, the ligands are named first and then the central metal ion.
(III) When more than one type of ligands are present, they are named in alphabetical order of preference without any consideration of charge.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The IUPAC name of the complex \(\left[\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{3} \mathrm{Br}\left(\mathrm{NO}_{2}\right) \mathrm{Cl}\right] \mathrm{Cl}\) is

(a) triamminechlorobromonitroplatinum (IV) chloride

(b) triamminebromonitrochloroplatinum (IV) chloride

(c) triamminebromidochloridonitroplatinum (IV) chloride

(d) triamminenitrochlorobromoplatinum (IV) chloride

(ii) The lUPAC name of [Ni(CO)₄] is

(a) tetracarbonylnickel (II)	(b) tetracarbonylnickel (0)
(c) tetracarbonylnickelate (II)	(d) tetracarbonylnickelate (0).

(iii) As per IUPAC nomenclature, the name of the complex \(\left[\mathrm{Co}\left(\mathrm{H}_{2} \mathrm{O}\right)_{4}\left(\mathrm{NH}_{3}\right)_{2}\right] \mathrm{Cl}_{3}\) is

(a) tetraaquadiamminecobalt (II) chloride	(b) tetraaquadiamminecobalt (III) chloride
(c) diamminetetraaquacobalt (II) chloride	(d) diamminetetraaquacobalt (III) chloride

(iv) Which of the following represents correct formula of dichloridobis( ethane-1, 2-diamine ) cobalt (III) ion?

(a) [CoCl₂(en)]²⁺

(b) [Co(ONO)(NH₃)₅]SO₄

(c) [Co(NO₂)(NH₃)₄] (SO₄)₂

(d) [Co(NO)(NH₃)₄] (SO₄)₂

3)

Read the passage given below and answer the following questions:
Iron forms many complexes in its +2 and +3 oxidation states such as \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{2+}(A) ;\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{4-}(B)\) \(\left[\mathrm{Fe}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}(C) ;\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}(D)\) ,etc., They exhibit, different magnetic properties and undergo different hybridisation of iron.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Which of the following statements is correct?

(a) (B) is paramagnetic while (C) is diamagnetic.

(b) Both (B) and (D) are outer orbital complexes.

(c) Both (A) and (C) are paramagnetic.

(d) (A) is outer orbital complex and (C) is inner orbital complex.

(ii) The complex having maximum magnetic moment is

(a) (A)

(b) (B)

(c) (C)

(d) (D)

(iii) The spin only magnetic moment of complexes (A), (B), (C) and (D) are respectively (in BM)

(a) \(2 \sqrt{6}, 0, \sqrt{35}, \sqrt{3}\)

(b) \(0,2 \sqrt{6}, \sqrt{35}, \sqrt{3}\)

(c) \(\sqrt{15}, 2 \sqrt{6}, \sqrt{3}, 0\)

(d) \(\sqrt{3}, \sqrt{8}, 0, \sqrt{15}\)

(iv) Which of the given complexes are outer orbital complexes?

(a) (A) and (B) only

(b) (B) and (C) only

(c) (A) and (C) only

(d) (B) and (D) only

4)

Read the passage given below and answer the following questions:
To explain bonding in coordination compounds various theories were proposed. One of the important theory was valence bond theory. According to that, the central metal ion in the complex makes available a number of empty orbitals for the formation ofcoordination bonds with suitable ligands. The appropriate atomic orbitals of the metal hybridise to give a set of equivalent orbitals of definite geometry. The d-orbitals involved in the hybridisation may be either inner d-orbitals i.e., (n - 1) d or outer d-orbitals i.e., nd. For example, CO³⁺ forms both inner orbital and outer orbital complexes, with ammonia it forms [Co(NH₃)₆]³⁺ and with fluorine it forms [CoF₆]^3- complex ion.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Which of the following is not true for [CoF₆]^3- ?

(a) It is paramagnetic.	(b) It has coordination number of 6.
(c) It is outer orbital complex.	(d) It involves d²sp³ hybridisation.

Which of the following is true for [Co(NH₃)₆]³⁺?

(a) It is an octahedral, dimagnetic and outer orbital complex.

(b) It is an octahedral, paramagnetic and outer orbital complex.

(c) It is an octahedral, paramagnetic and inner orbital complex.

(d) It is an octahedral, dimagnetic and inner orbital complex.

(iii) The paramagnetism of [CoF₆]^3- is due to

(a) 3 electrons

(b) 4 electrons

(c) 2 electrons

(d) 2 electrons

(iv) Which of the following is an inner orbital or low spin complex?

(a) \(\left[\mathrm{Ni}\left(\mathrm{H}_{2} \mathrm{O}\right)_{6}\right]^{3+}\)

(b)\(\left[\mathrm{FeF}_{6}\right]^{3-}\)

(c) \(\left[\mathrm{Co}(\mathrm{CN})_{6}\right]^{3-}\)

(d) \(\left[\mathrm{NiCl}_{4}\right]^{2-}\)

5)

Read the passage given below and answer the following questions:
Valence bond theory considers the bonding between the metal ion and the ligands as purely covalent. On the other hand, crystal field theory considers the metal-ligand bond to be ionic arising from electrostatic interaction between the metal ion and the ligands. In coordination compounds, the interaction between the ligand and the metal ion causes the five d-orbitals to split-up. This is called crystal field splitting and the energy difference between the two sets of energy level is called crystal field splitting energy. The crystal field splitting energy (Δ_o) depends upon the nature of the ligand. The actual configuration of complexes is divided by the relative values of Δ_o and P (pairing energy)
If Δ_o < P, then complex will be high spin.
If Δ_o > P, then complex will be low spin.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Which of the following ligand has lowest Δ_o value?

(a) CN^-

(b) CO

(c) F^-

(d) NH₃

(ii) The crystal field splitting energy for octahedral (Δ_o) and tetrahedral (Δ_t) complex is related as

(a) \( \Delta_{t}=\frac{1}{2} \Delta_{o}\)	(b) \(\Delta_{t}=\frac{4}{9} \Delta_{o}\)
(c) \(\Delta_{t}=\frac{3}{5} \Delta_{o}\)	(d) \(\Delta_{t}=\frac{2}{5} \Delta_{o}\)

(iii) On the basis of crystal field theory, the electronic configuration of d⁴ in two situations: (i) Δ_o > P and (ii) Δ_o< P are

(i)	(ii)
(a) \(t_{2 g}^{4} e_{g}^{0}\)	\(t_{2 g}^{3} e_{g}^{1}\)
(b) \(t_{2 g}^{3} e_{g}^{1}\)	\(t_{2 g}^{4} e_{g}^{0}\)
(c) \(t_{2 g}^{3} e_{g}^{1}\)	\(t_{2 g}^{3} e_{g}^{1}\)
(d) \(t_{2 g}^{4} e_{g}^{0}\)	\(t_{2 g}^{4} e_{g}^{0}\)

(iv) Using crystal field theory, calculate magnetic moment of central metal ion of [FeF₆]^4-.

(a) 1.79 B.M.

(b) 2.83 B.M.

(c) 3.85 B.M.

(d) 4.9 B.M.

CBSE 12th Standard Chemistry Subject The d- and f- Block Elements Chapter Case Study Questions With Solution 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
The f-block elements are those in which the differentiating electron enters the (n -2) forbital. There are two series of f-block elements corresponding to filling of 4f and 5f-orbitals. The series of 4f- orbitals is called lanthanides. Lanthanides show different oxidation states depending upon stability of f⁰, f⁷ and f¹⁴ configurations, though the most common oxidation states is +3. There is a regular decrease in size of lanthanides ions with increase in atomic number which is known as lanthanide contraction.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The atomic numbers of three lanthanide elements X, Y and 2 are 65, 68 and 70 respectively, their Ln³⁺ electronic configuration is

(a) 4f⁸, 4f¹¹, 4f¹³

(b) 4f¹¹, 4f⁸ , 4f¹³

(c) 4f^o, 4f², 4f¹¹

(d) 4f³, 4f⁷, 4f⁹

(ii) Lanthanide contraction is observed in

(a) Gd

(b) At

(c) Xe

(d) Te

(iii) Name a member of the lanthanoid series which is well known to exhibit +4 oxidation state.

(a) Cerium (Z = 58)

(b) Europium (Z = 63)

(c) Lanthanum (Z = 57)

(d) Gadolinium (Z = 64)

(iv) Identify the incorrect statement among the following.

(a) Lanthanojd contraction is the accumulation of successive shrinkages.

(b) The different radii of Zr and Hf due to consequence of the lanthanoid contraction.

(c) Shielding power of 4f electrons is quite weak.

(d) There is a decrease in the radii of the atoms or ions as one proceeds from La to Lu.

2)

Read the passage given below and answer the following questions:
The transition elements have incompletely filled d-subshells in their ground state or in any of their oxidation states. The transition elements occupy position in between s- and p-blocks in groups 3-12 of the Periodic table. Starting from fourth period, transition elements consists of four complete series : Sc to Zn, Y to Cd and La, Hf to Hg and Ac, Rf to Cn. In general, the electronic configuration of outer orbitals of these elements is (n - 1) d^1-10 ns^1-2. The electronic configurations of outer orbitals of Zn, Cd, Hg and Cn are represented by the general formula (n - 1)d¹⁰ n². All the transition elements have typical metallic properties such as high tensile strength, ductility, malleability. Except mercury, which is liquid at room temperature, other transition elements have typical metallic structures. The transition metals and their compounds also exhibit catalytic property and paramagnetic behaviour. Transition metal also forms alloys. An alloy is a blend of metals prepared by mixing the components. Alloys may be homogeneous solid solutions in which the atoms of one metal are distributed randomly among the atoms of the other.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Which of the following characteristics of transition metals is associated with higher catalytic activity?

(a) High enthalpy of atomisation	(b) Variable oxidation states
(c) Paramagnetic behaviour	(d) Colour of hydrated ions

(ii) Transition elements form alloys easily because they have

(a) same atomic number	(b) same electronic configuration
(c) nearly same atomic size	(d) same oxidation states.

(iii) The electronic configuration of tantalum (Ta) is

(a) \([\mathrm{Xe}] 4 f^{0} 5 d^{1} 6 s^{2}\)	(b) \([\mathrm{Xe}) 4 f^{14} 5 d^{2} 6 s^{2}\)
(c) \([\mathrm{Xe}] 4 f^{14} 5 d^{3} 6 s^{2}\)	(d) \(\left[\mathrm{Xe}\left]4 f^{14} 5 d^{4} 6 s^{2}\right.\right.\)

(iv) Which one of the following outer orbital configurations may exhibit the largest number of oxidation states?

(a) 3d⁵4s¹

(b) 3d⁵4s²

(c) 3d²4s²

(d) 3d³4s²

3)

Read the passage given below and answer the following questions:
The unique behaviour of Cu, having a positive E^oaccounts for its inability to liberate H₂ from acids. Only oxidising acids (nitric and hot concentrated sulphuric acid) react with Cu, the acids being reduced. The stability of the half-filled (d⁵) subshell in Mn²⁺ and the completely filled (d¹⁰ ) configuration in Zn²⁺ are related to their E^o (M³⁺ /M²⁺) values. The low value for Sc reflects the stability of Sc³⁺ which has a noble gas configuration. The comparatively high value for Mn shows that Mn²⁺(d⁵) is particularly stable, whereas a comparatively low value for Fe shows the extra stability of Fe³⁺ (d⁵). The comparatively low value for V is related to the stability of V²⁺ (half-filled t_2g level).
The following questions are multiple choice questions.Choose the most appropriate answer :
(i) Standard reduction electrode potential of Zn²⁺ /Zn is - 0.76 V. This means

(a) ZnO cannot be reduced to Zn by H₂ under standard conditions

(b) Zn cannot liberate H₂ with concentrated acids

(c) Zn is generally the anode in an electrochemical cell

(d) Zn is generally the cathode in an electrochemical cell.

(ii) E^ovalues for the couples Cr³⁺/Cr²⁺ and Mn³⁺ /Mn²⁺ are -0.41 and +1.51 volts respectively. These values suggest that

(a) Cr²⁺ acts as a reducing agent whereas Mn3+ acts as an oxidizing agent

(b) Cr²⁺ is more stable than Cr³⁺ state

(c) Mn³⁺ is more stable than Mn²⁺

(d) Cr²⁺ acts as an oxidizing agent whereas Mn³⁺ acts as a reducing agent

(iii) The reduction potential values of M, Nand O are +2.46, -1.13 and -3.13 Y respectively. Which of the following order is correct regarding their reducing property?

(a) O>N>M

(b) O>M>N

(c) M>N>O

(d) M>O>N

(iv) Which of the following statements are true?
(i) Mn²⁺ compounds are more stable than Fe²⁺ towards oxidation to +3 state.
(ii) Titanium and copper both in the first series of transition metals exhibits +1 oxidation state most frequently.
(iii) Cu⁺ ion is stable in aqueous solutions.
(iv) The E⁰ value for the Mn³⁺ /Mn²⁺ couple is much more positive than that for Cr³⁺/Cr²⁺ or Fe³⁺/Fe²⁺.

(a) (ii) and (iii)

(b) (i) and (iv)

(c) (i) and (iii)

(d) (ii) and (iv)

4)
Read the passage given below and answer the following questions:
Transition metal oxides are compounds formed by the reaction of metals with oxygen at high temperature. The highest oxidation number in the oxides coincides with the group number. In vanadium, there is a gradual change from the basic V₂O₃ to less basic V₂O₄ and to amphoteric V₂O_5・V₂O₄ dissolves in acids to give VO²⁺ salts. Transition metal oxides are commonly utilized for their catalytic activity and semiconductive properties. Transition metal oxides are also frequently used as pigments in paints and plastic. Most notably titatnium dioxide. One of the earliest application of transition metal oxides to chemical industry involved the use of vanadium oxide for catalytic oxidation of sulfur dioxide to sulphuric acid. Since then, many other applications have emerged, which include benzene oxidation to maleic anhydride on vandium oxides; cyclohexane oxidation to adipic acid on cobalt oxides. An important property of the catalyst material used in these processes is the ability of transition metals to change their oxidation state under a given chemical potential of reductants and oxidants.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Which oxide of vanadium is most likely to be basic and ionic ?

(a) VO (b) V₂O₃ (c) VO₂ (d) V₂O₅

(ii) Vanadyl ion is

(a) VO²⁺ (b) VO₂⁺ (c) V₂O⁺ (d) VO₄^3-

(iii) The oxidation state of vanadium in V₂O₅ is

(a) +5/2 (b) +7 (c) +5 (d) +6

(iv) Identify the oxidising agent in the following reaction.

(a) V₂O₅ (b)Ca (c) V (d) None of these
5)
Read the passage given below and answer the following questions:
Transition elements are elements that have partially filled d-orbitals. The configuration of these elements corresponds to (n - 1)d^1-10ns^1-2. It is important to note that the elements mercury, cadmium and zinc (Ire not considered transition elements because of their electronic configurations, which corresponds to (n - 1)d^1-10ns².
Some general properties of transition elements are :
These elements can form coloured compounds and ions due to d-d transition;
These elements exhibit many oxidation states;
A large variety of ligands can bind themselves to these elements, due to this, a wide variety of stable complexes formed by these ions. The boiling and melting point of these elements are high. These elements have a large ratio of charge to the radius.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Tungsten has very high melting point.
Reason: Tungsten is a covalent compound.
(ii) Assertion: Zn, Cd and Hg are normally not considered transition metals.
Reason: d-Orbitals in Zn, Cd and Hg elements are completely filled, hence these metals do not show the general characteristics properties of the transition elements.
(iii) Assertion: Copper metal gets readily corroded in acidic aqueous solution such as HCI and dil. H₂SO₄
Reason: Free energy change for this process is positive.
(iv) Assertion: Tailing of mercury occurs on passing ozone through it.
Reason: Due to oxidation of mercury.

CBSE 12th Standard Chemistry Subject The p-Block Elements Chapter Case Study Questions With Solution 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
Under the normal conditions, noble gases are monoatomic and have closed shell electronic configuration. Lighter noble gases have low boiling points due to weak dispersion forces between the atoms and the absence of other interatomic interactions. Xenon, one of the important noble gas, forms a series of compounds with fluorine with oxidation number +2, +4 and +6. All xenon fluorides are strong oxidising agents. XeF₄ reacts violently with water to give XeO₃. The geometry of xenon compounds can be deduced by considering the total number of electron pairs in their valence shell.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Among noble gases (from He to Xe) only xenon reacts with fluorine to form stable xenon fluorides because xenon

(a) has the largest size

(b) has the lowest ionisation enthalpy

(c) has the highest heat of vapourisation

(d) is the most readily available noble gas.

(ii) The structure of XeO₃ is

(a) square planar

(b) pyramidal

(c) linear

(d) T-shaped.

(iii) In the preparation of compound of xenon, Bartlett had taken \(\mathrm{O}_{2}^{+} \mathrm{PtF}_{6}^{-}\) as a base compound. This is because

(a) both O₂ and Xe have same size

(b) both Xe and O₂ have same electron gain enthalpy

(c) both have almost same ionisation enthalpy

(d) both Xe and O₂ are gases.

(iv) The oxidation state of xenon in XeO₃ is

(a) +4

(b) +2

(c) +8

(d) +6

2)
Read the passage given below and answer the following questions :
Interhalogen compounds are formed when halogen group elements react with each other. These are the compounds which consist of two or more different elements of group - 17. A halogen with large size and low electronegativity reacts with an element of group - 17 with small size and high electronegativity. As the ratio of radius of larger and smaller halogen increases, the number of atoms in a molecule also increases.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) The stability of interhalogen compounds follows the order

(a) IF₃> BrF₃ > ClF₃ (b) ClF₃ > BrF₃ > IF₃

(c) BrF₃ > IF₃> ClF₃ (d) ClF₃ > IF₃ > BrF₃

(ii) Identify the correct match from the following.

(a) [ICl₂]^--bent (b) IF₇ - pentagonal bipyramidal

(c) ClF₃ - trigonal planar (d) [BrF₄r]^--square pyramidal

(iii) In XA_5, the central atom has (both X and A are halogens)

(a) 5 bond pairs and no lone pairs (b) 5 bond pairs and one lone pair

(c) 6 bond pairs and no lone pairs (d) 4 bond pairs and one lone pair.

(iv) In the known interhalogen compounds, the maximum number of atoms are

(a) 4 (b) 5

(c) 8 (d) 7
3)
Read the passage given below and answer the following questions :
Noble gases are inert gases with general electronic configuration of ns²np⁶. These are mono atomic, colourless, odourless and tasteless gases. The first compound of noble gases was obtained by the reaction of Xe with PtF₆. A large number of compounds of Xe and fluorine have been prepared till now. The structure of these compounds can be explained on the basis of VSEPR theory as well as concept of hybridisation. The compounds of krypton are fewer. Only the difluoride of krypton (KrF₂) has been studied in detail. Compounds of radon have not isolated but only identified by radio tracer technique. However, no true compounds of helium, neon or argon are yet known.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The formula of the compound when Xe and PtF₆ are mixed, is

(a) XeF₆ (b) XeF₄ (c) Xe₂PtF₆ (d) Xe+[PtF₆]^-

(ii) Which of the following is not formed by Xe?

(a) XeF_s (b) XeF (c) XeF₃ (d) All of these

(iii) The number of lone pairs and bond pairs of electrons around Xe in XeOF₄ respectively are

(a) O and 5 (b) 1 and 5 (c) 1 and 4 (d) 2 and 3

(iv) Which of the following compounds has more than one lone pair of electrons around central atom?

(a) XeO₃ (b) XeF₂ (c) XeOF₄ (d) XeO₂F₂

4)

Read the passage given below and answer the following questions:
All the elements of group 16 have ns² np⁴ configuration in their outermost shell. Therefore, the atoms of these elements try to gain or share two electrons to achieve noble gas configuration. Sulphur and other elements of group 16 are less electronegative than oxygen, so, they cannot accept electrons easily. By sharing of two electrons with other elements, these elements acquire ns² np⁶configuration and exhibit +2 oxidation state. Except oxygen, group 16 elements have vacant d-orbitals in their valence shell to which electrons can be promoted from p- and s-orbitals of the same shell. As a result, they can show +4 and +6 oxidation states also.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Oxygen shows +2 oxidation state in

(a) OF₂

(b) H₂O

(c) Cl₂O

(d) H₂O₂

(ii) Like sulphur, oxygen is not able to show +4 and +6 oxidation states because

(a) oxygen is a gas while sulphur is a solid

(b) sulphur has high ionisation enthalpy as compared to oxygen

(c) oxygen has no d-orbitals in its valence shell

(d) oxygen has high electron affinity as compared to sulphur.

(iii) Oxidation state of sulphur in Na₂S₄O₆

(a) 7/2

(b) 5/2

(c) 1/2

(d) 3/2

(iv) The oxidation states of sulphur in S_8' SO₃ and H₂S are respectively

(a) 0, +6 and -2

(b) +6,0 and -2

(c) -2,0 and +6

(d) +2, +6 and -2

5)

Read the passage given below and answer the following questions:
Nitric acid reacts with most of the metals (except noble metals like gold and platinum) and non-metals. Towards its reaction with metals, HNO₃ acts as an acid as well as an oxidising agent. Like other acids, HNO₃ liberate nascent hydrogen from metals which further reduces the nitric acid into number of products like NO, NO₂, N₂O or NH₃. The different stages of reduction of nitric acid are:
\(\mathrm{HNO}_{3} \stackrel{+e^{-}}{\longrightarrow} \mathrm{NO}_{2} \stackrel{+4}{\longrightarrow} \stackrel{+2 e^{-}}{\longrightarrow} \mathrm{NO} \frac{+2^{-}}{\mathrm{NaOH}} \stackrel{+1}{\mathrm{~N}}_{2} \mathrm{O} \stackrel{+4 e^{-}}{\longrightarrow} \stackrel{-3}{\mathrm{NH}}_{3}\)
The product of the reduction of HNO₃depends upon the nature of the metal, concentration of nitric acid and temperature.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Which of the following reactions Is used to prepare laughing gas?

(a) \(\mathrm{Pb}+\text { dil. } \mathrm{HNO}_{3} \longrightarrow\)	(b) \(\mathrm{Hg}+\text { dil. } \mathrm{HNO}_{3} \longrightarrow\)
(c) \(\mathrm{Zn}+\mathrm{dil} . \mathrm{HNO}_{2} \longrightarrow\)	(d) \(\mathrm{Cu}+\text { dil. } \mathrm{HNO}_{3} \longrightarrow\)

(ii) Gold and platinum does not dissolve in HN03 but soluble in 1 : 3 mixture of HNO₃ and HCI due to the formation of respectively

(a) Au(NO₃)_2' [Pt(NO₃)₂]	(b) H[AuCI₄], H₂[PtCI₆]
(c) [AuCI₆]^2-, [PtCI₂]^2-	(d) [Au(NO₃)₄]⁺, [Pt(NO₃)6]^2-

(iii) Identify B in the following reaction.
\(\mathrm{Cu}+\mathrm{HNO}_{3(\text { conc. })} \rightarrow(A)+(B)+\mathrm{H}_{2} \mathrm{O}\)
Deep blue colour Gas

(a) NO₂

(b) N₂

(c) NO

(d) N₂O

(iv) In which of the following reactions HN03 will not act as an oxidising agent?

(a) \(\mathrm{HNO}_{3}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow\)	(b) \(\mathrm{HNO}_{3}+\mathrm{FeSO}_{4}+\mathrm{H}_{2} \mathrm{SO}_{4} \rightarrow\)
(c) \(\mathrm{KI}+\mathrm{HNO}_{3} \rightarrow\)	(d) \(\mathrm{Au}+\mathrm{HNO}_{3} \rightarrow\)

CBSE 12th Standard Chemistry Subject Surface Chemistry Chapter Case Study Questions With Solution 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions :
Adsorption depends on the nature of the adsorbent. The rough solid surface has more number of pores and adsorb more number of gases than the smooth surface. Most common adsorbents are silica gel, activated charcoaL The extent of adsorption also depends on the surface area of the solid. Specific surface area of an adsorbent is the surface area available for adsorption per gram of the adsorbent. The greater the surface area of the solid, the greater would be the adsorption. Charcoal is a more effective adsorbent than solid wood. Desorption is a process of removing an adsorbed substance from a surface on which it is absorbed.
Physisorption is non-specific and any gas can be adsorbed. But the gases which are easily liquefiable (e.g., NH₃ , HCl, CO₂ ) are adsorbed at a faster rate and to a large extent than the gases which are difficult to liquefy (e.g., H₂ , O_2, N₂ ). It depends on the critical temperature. Higher the critical temperature of a gas, more easily liquefiable the gas is and more is the rate of adsorption. Chemisorption is specific in nature. Therefore, only those gases can be adsorbed which are capable of forming chemical bonds with the adsorbent.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) Select the correct statement regarding desorption.

(a) It is done by cooling or by increasing the pressure applied.

(b) It is done by cooling or by reducing the pressure applied.

(c) It is done by heating or by reducing the pressure applied

(d) It is done by heating or by increasing the pressure applied.

(ii) Which of the following statements regarding the physical adsorption of a gas on surface of solid is not correct?

(a) On increasing temperature, adsorption increases continuously

(b) Enthalpy changes are negative

(c) It is non-specific in nature

(d) It is reversible in nature

(iii) At the same temperature and pressure, select the correct order of adsorption of the following gases on the same mass of charcoal.

(a) SO₂> CH₄ > H₂	(b) CH₄ < SO₂ < H₂
(c) H_z> CH₄ > SO₂	(d) CH₄ < H₂ < SO₂

(iv) Select the incorrect statement among the following.

(a) Physical adsorption occurs at a low temperature and chemisorption occurs at all temperature

(b) In physisorption heat of adsorption is low while in chemisorption it is high

(c) Chemisorption is irreversible and physisorption is reversible

(d) Magnitude of chemisorption decreases with rise in temperature while physisorption increases with rise in temperature.

2)
Read the passage given below and answer the following questions :
A graph between the amount adsorbed (x/m) by an adsorbent and the equilibrium pressure of the adsorbate at a constant temperature is called the adsorption isotherm. A relationship between the amount adsorbed (x/m) and the equilibrium pressure (P) can be obtained as follows:

In the intermediate range of pressure, x/m = kP^1/n (was originally put forward by Freundlich and is known as Freundlich adsorption isotherm).
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) According to Freundlich adsorption isotherm, which of the following is correct?

(a) \(\frac{x}{m} \propto P^{0}\) (b) \(\frac{x}{m} \propto P^{1}\)

(c) \(\frac{x}{m} \propto P^{1 / n}\) (d) All the above are correct for different range of pressure

(ii) In the Freundlich adsorption isotherm equation
\(\log \frac{x}{m}=\log k+\frac{1}{n} \log p\) ,the value of 1/n is

(a) any value from 0 to 1 (b) a negative integer

(c) a positive integer (d) a positive or a negative fractional number.

(iii) Plot of log xlm against log p is a straight line inclined at an angle of 45°. When the pressure is 0.5 atm and Freundlich parameter, k is 10, the amount of solute adsorbed per gram of adsorbent will be (log 5 = 0.6990)

(a) 1g (b) 2g (c) 3g (d) 5g

(iv) In the plot of log \(\frac{x}{m}\) vs log p for an adsorption, a straight line inclined at an angle of \(\theta=14.04^{\circ}\) to the x-axis was obtained.The 'n' value for this adsorption process is (tan 14.04° = 0.25)

(a) 5 (b) 8 (c) 4 (d) 2
3)
Read the passage given below and answer the following questions :
Hardy Schulze rule states that the precipitating effect of an ion on dispersed phase of opposite charge increases with the valency of the ion. The higher the valency of the flocculating ion, the greater is its precipitating power. Thus, for the precipitation of AS₂ S₃ sol (-ve sol) the precipitating power of Al³⁺, Ba²⁺ and Na⁺ions is of the order, Al³⁺> Ba²⁺ > Na⁺. Similarly, for precipitating Fe(OH)₃ sol (-ve sol) the precipitating power of \(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}\)\(\mathrm{SO}_{4}^{2-}\) and Cl^- is of the order,\(\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]^{3-}>\mathrm{SO}_{4}^{2-}>\mathrm{Cl}^{-}\) . The minimum concentration of an electrolyte in millimoles per litre required to cause precipitation of a sol in 2 hours is called flocculation value. The smaller the flocculation value, the higher will be the coagulating power of the ion. The minimum mass of the protective colloid (lyophilic colloid) in milligrams that must be added to 10 mL of a standard red gold sol so that no coagulation occurs when 1 mL of 10% NaCl solution is rapidly added to it is called the gold number of the protective colloid.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The gold number of four protective colloids A, B, C and Dare 0.03, 0.003, 10 and 30 respectively. Protective power of these colloids will be of the order:

(a) B > A > C > D (b) A > B > C > D (c) C >B> D > A (d) D > A > C >

(ii) Which of the following has least flocculating value for positive sol?

(a) Cl^- (b) \(\mathrm{SO}_{4}^{2-}\) (c) \(\mathrm{PO}_{4}^{3-}\) (d) [Fe(CN₆)^4-

(iii) Which of the following colloidal solutions is positively charged?

(a) TiO₂ (b) AS₂ S₃ (c) Blood (d) Gold sol

(iv) The coagulation value in millimoles per litre of electrolytes used for the coagulation of As₂ S₃ are as below:

I. NaCl = 52 II. KCl = 50 III. BaCl₂ = 0.69 IV. MgSO₄ = 0.72

The correct order of their flocculating power is

(a) I > II > III > IV (b) I > II > IV > III (c) I < II < IV <III (d) IV < I < II < III

4)

Read the passage given below and answer the following questions :
Adsorption is a spontaneous process and involves unequal distribution of the molecules of the gaseous substance on the surface of solid or liquid. Adsorption is an exothermic process. The attractive forces between adsorbate and adsorbent are either van der Waals' forces or chemical bonds. Adsorption of gases on solids is generally controlled by the factors like temperature, pressure and nature of adsorbate and adsorbent.
The following questions are multiple choice questions.Choose the most appropriate answer:
(i) In physisorption process, the attractive forces between adsorbate and adsorbent are

(a) covalent bonds	(b) ionic bonds
(c) van der Waals' force	(d) H-bonds

(ii) Which of the following graph represents the variation of physical adsorption with temperature?

(iii) Which one of the following processes does not use adsorption?

(a) Froth floatation process	(b) Chromatography
(c) Decolourisation of sugar liquors	(d) Dissolution of sugar in water

(iv) Which of the following statements is true?

(a) Chemisorption forms unimolecular layer

(b) Chemisorption is a reversible process.

(c) Chemisorption is independent of pressure.

(d) Chemisorption has low enthalpy change.

5)

Read the passage given below and answer the following questions :
Colloidal particles carry either positive or negative charge. The nature of this charge is the same on all the dispersed particles in a given colloidal solution and may be either positive or negative. When two or more ions are present in the dispersion medium, preferential adsorption of the ion common to the colloidal particles usually takes place. When KI solution is added to the AgNO₃ solution till KI is in excess, the precipitated silver iodide adsorbs iodide ions from the dispersion medium, and negatively charged colloidal solution results. If the colloidal sol of AgI is prepared by adding AgNO₃ solution to KI solution till AgNO₃ is in slight excess, Ag⁺ ions will be adsorbed giving positive charge to the colloidal particles. The combination of the two layers of opposite charges around the colloidal particles is called Helmholtz electrical double layer. The presence of equal and similar charges on colloidal particles is largely responsible for providing stability to the colloidal solution.
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.

(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.

(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.

(c) Assertion is correct statement but reason is wrong statement

(d) Assertion is wrong statement but reason is correct statement.

(i) Assertion : The presence of electric charge on colloidal particles is indicated by electrophoresis.
Reason : Lyophilic sols, in contrast to lyophobic sols are easily coagulated on addition of small amounts of electrolytes.
(ii) Assertion : Gold number is a measure of protective action by a lyophilic colloid on a lyophobic colloid.
Reason : Zeta potential (or electrokinetic potential) is the potential difference between fixed charged layer and the diffused layer having opposite charge.
(iii) Assertion: The presence of equal and similar charges on colloidal particles islargely responsible in providing stability to the colloidal solution.
Reason : The repulsive forces between charged particles having the same charge prevent them from aggregating and provide stability.
(iv) Assertion: When FeCl₃ is added to an excess of hot water, a positively charged sol of hydrated ferric oxide is formed.
Reason : When ferric chloride is added to NaOH solution a negatively charged sol is obtained due to adsorption of OH^-ions.

CBSE 12th Standard Chemistry Subject Chemical Kinetics Chapter Case Study Questions With Solution 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)
Read the passage given below and answer the following questions :
The progress of the reaction, \(A \rightleftharpoons n B\) with time is represented in the following figure.

The following questions are multiple choice questions. Choose the most appropriate answer:
(i) What is the value of n?

(a) 1 (b) 2 (c) 3 (d) 4

(ii) Find the-value of the equilibrium constant

(a) 0.6 M (b) 1.2M (c) 0.3M (d) 2.4M

(iii) The initial rate of conversion of A will be

(a) 0.1 mol L^-1 hr^-1 (b) 0.2 mol L^-1 hr^-1 (c) 0.4 mol L^-1 hr^-1 (d) 0.8 mol L^-1 hr^-1

(iv) For the reaction, if \(\frac{d[B]}{d t}=2 \times 10^{-4}\) , value of \(-\frac{d[A]}{d t}\) will be

(a) 2 x 10^{- 4} (b) 10^-4 (c) 4 x 10^{- 4} (d) 0.5 x 10^{- 4}

2)

Read the passage given below and answer the following questions:
For the reaction: \(2 \mathrm{NO}_{(g)}+\mathrm{Cl}_{2(g)} \rightarrow 2 \mathrm{NOCl}_{(g)}\), the following data were collected. All the measurements were taken at 263 K.

Experiment No.	Initial [NO] (M)	Initial [Cl₂] (M)	Initial rate of disapp. of Cl₂ (M/min)
1.	0.15	0.15	0.60
2.`	0.15	0.30	1.20
3.	0.30`	0.15	2.40
4	0.25	0.25	?

The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The molecularity of the reaction is

(a) 1

(b) 2

(c) 3

(d) 4

(ii) The expression for rate law is

(a) r = k[NO][Cl₂]

(b) r = k[NO]²[Cl₂ ]

(c) ) r = k[NO][Cl₂]²

(d) r = k[NO]²[Cl₂]²

(iii) The overall order of the reaction is

(a) 2

(b) 0

(c) 1

(d) 3

(iv) The value of rate constant is

(a) 150.32 M^-2min^-1

(b) 200.08 M^-1 min^-1

(c) 177.77 M^-2min^-1

(d) 155.75 M^-1 min^-1

3)
Read the passage given below and answer the following questions:
A reaction is said to be of the first order if the rate of the reaction depends upon one concentration term only. For a first order reaction of the type A \(\rightarrow\) Products, the rate of the reaction is given as : rate = k[A]. The differential rate law is given as \(\frac{d A}{d t}=-k[A]\) .The integrated rate law : In \(\frac{[A]}{[A]_{0}}=-k t\) where [A] is the concentration of reactant left at time t and [A]_o is the initial concentration of the reactant, k is the rate constant.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) The unit of rate constant for a first order reaction is

(a) s^-1 (b) mol L^-1 s^-1 (c) L mol^-1 s^-1 (d) L² mol^-2s^-1

(ii) Half-life period of a first order reaction is 10 min. Starting with initial concentration 12 M, the rate after 20 min is

(a) 0.693 x 3 M min^-1 (b) 0.0693 x 4 M min^-1 (c) 0.0693 M min^-1 (d) 0.0693 x 3 M min^-1

(iii) For a first order reaction, (A) \(\rightarrow\) products, the concentration of A changes from 0.1 M to 0.025 M in 40 minutes. The rate of reaction when the concentration of A is 0.01 M, is

(a) 3.47 x 10^-4 M/min (b) 3.47 x 10^-5 M/min (c) 1.73 x 10^-4 M/min (d) 1.73 x 10^-5 M/min

(iv) The half-life period of a 1^st order reaction is 60 minutes. What percentage will be left over after 240 minutes?

(a) 6.25% (b) 4.25% (c) 5% (d) 6%

4)

Read the passage given below and answer the following questions :
Number of molecules which must collide simultaneously to give product is called molecularity. It is equal to sum of coefficients of reactants present in stoichiometric chemical equation. For reaction, \(m_{1} A+m_{2} B \rightarrow \text { Product }\)
Molecularity = [m₁ + m₂ ]
In complex reaction each step has its own molecularity which is equal to the sum of coefficients of reactants present in a particular step. Molecularity is a theoretical property. Its value is any whole number. Number of concentration terms on which rate of reaction depends is called order of reaction or sum of powers of concentration terms present in the rate equation is called order of reaction.
If rate equation of reaction is : Rate = \(k \cdot C_{A}^{m_{1}} \cdot C_{B}^{m_{2}}\)
Then order of reaction = m₁ + m₂
In simple reaction, order and molecularity are same. In complex reaction, order of slowest step is the order of over all reaction. This step is known as rate determining step. Order is an experimental property. Its value may be zero, fractional or negative.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Higher order (> 3) reactions are rare due to

(a) shifting of equilibrium towards reactants due to elastic collisions

(b) loss of active species on collision

(c) low probability of simultaneous collision of all the reacting species

(d) increase in entropy and activation energy as more molecules are involved

(ii) The molecularity of the reaction:
\(6 \mathrm{FeSO}_{4}+3 \mathrm{H}_{2} \mathrm{SO}_{4}+\mathrm{KClO}_{3} \rightarrow \mathrm{KCl}+3 \mathrm{Fe}_{2}\left(\mathrm{SO}_{4}\right)_{3}+3 \mathrm{H}_{2} \mathrm{O} \text { is }\)

(a) 6

(b) 3

(c) 10

(d) 7

(iii) Which of the following statements is false in the following?

(a) Order of a reaction may be even zero

(b) Molecularity of a reaction is always a whole number.

(c) Molecularity and order always have same values for a reaction.

(d) Order of a reaction depends upon the mechanism of the reaction.

(iv) The rate of the reaction \(A+B+C \rightarrow \text { products }\) , is given by \(r=-\frac{d[A]}{d t}=k[A]^{1 / 2}[B]^{1 / 3}[C]^{1 / 4}\) ,The order of the reaction is

(a) \(\frac{1}{3}\)

(b) \(\frac{1}{4}\)

(c) \(\frac{1}{2}\)

(d) \(\frac{13}{12}\)

5)
Read the passage given below and answer the following questions :
In a reaction, the rates of disappearance of different reactants or rates of formation of different products may not be equal but rate of reaction at any instant of time has the same value expressed in terms of any reactant or product. Further, the rate of reaction may not depend upon the stoichiometric coefficients of the balanced chemical equation. The exact powers of molar concentrations of reactants on which rate depends are found experimentally and expressed in terms of 'order of reaction'. Each reaction has a characteristic rate constant depends upon temperature. The units of the rate constant depend upon the order of reaction.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) The rate constant of a reaction is found to be 3 x 10^-3 mol^-2 L²sec^-1.The order of the reaction is

(a) 0.5 (b) 2 (c) 3 (d) 1

(ii) In the reaction \(A+3 B \rightarrow 2 C\) ,the rate of formation of C is

(a) the same as rate of consumption of A (b) the same as the rate of consumption of B

(c) twice the rate of consumption of A (d) 3/2 times the rate of consumption of B.

(iii) Rate of a reaction can be expressed by following rate expression, Rate = k[A]² [B], if concentration of A is increased by 3 times and concentration of B is increased by 2 times, how many times rate of reaction increases?

(a) 9 times (b) 27 times (c) 18 times (d) 8 times

(iv) The rate of a certain reaction is given by,rate = k[H⁺]ⁿ . The rate increases 100 times when the pH changes from 3 to 1. The order (n) of the reaction is

(a) 2 (b) 0 (c) 1 (d) 1.5

CBSE 12th Standard Chemistry Subject Electrochemistry Case Study Questions With Solution 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)
Read the passage given below and answer the following questions:
Molar conductivity of ions are given as product of charge on ions to their ionic mobilities and Faraday's constant.
\(\lambda_{A^{n+}}=n \mu_{A^{n+}} F\) (here \(\mu\) is the ionic mobility of Aⁿ⁺).
For electrolytes say A_XB_y, molar conductivity is given by
\(\lambda_{m\left(A_{x} B_{y}\right)}=x_{n} \mu_{A^{n+}} F+y_{m} \lambda_{A^{m}-F}\)

Ions Ionic mobility

K⁺ 7.616 x 10^{- 4}

Ca²⁺ 12.33 x 10^-4

Br^- 8.09 x 10^{- 4}

\(\mathrm{SO}_{4}^{2-}\) 16.58 x 10^{- 4}

The following questions are multiple choice questions. Choose the most appropriate answer
(i) At infinite dilution, the equivalent conductance of CaSO₄ is

(a) 256 x 10^-4 (b) 279 (c) 23.7 (d) 2.0 x 10^{- 8}

(ii) If the degree of dissociation of CaSO₄ solution is 10% then equivalent conductance of CaSO₄ is

(a) 3.59 (b) 36.9 (c) 27.9 (d) 30.6

(iii) What is the unit of equivalent conductivity?

(a) ohm^-1 cm² eq^-1 (b) ohm cm²eq^-1

(c) ohm^-1 cm eq^-1 (d) ohm cm² eq^-1

(iv) If the molar conductance value of Ca²⁺ and Cl^-at infinite dilution are 118.88 x 10^-4m² mho mol^-1 and 77.33 x 10^-4 m²mho mol^-1respectively then the molar conductance of CaCl₂ (in m² mho mol^-1) will be

(a) 120.18 x 10^{- 4} (b) 135 x 10^-4 (c) 273.54 x 10^-4 (d) 192.1 x 10^-4
2)
Read the passage given below and answer the following questions:
Standard electrode potentials are used for various processes:
(i) It is used to measure relative strengths of various oxidants and reductants.
(ii) It is used to calculate standard cell potential.
(iii) It is used to predict possible reactions.
A set of half-reactions (in acidic medium) along with their standard reduction potential, E^o (in volt) values are given below
\(\mathrm{I}_{2}+2 e^{-} \rightarrow 2 \mathrm{I}^{-} ; \quad E^{\circ}=0.54 \mathrm{~V}\)
\(\mathrm{Cl}_{2}+2 e^{-} \rightarrow 2 \mathrm{Cl}^{-} ; \quad E^{\circ}=1.36 \mathrm{~V}\)
\(\mathrm{Mn}^{3+}+e^{-} \rightarrow \mathrm{Mn}^{2+} ; \quad E^{\circ}=1.50 \mathrm{~V}\)
\(\mathrm{Fe}^{3+}+e^{-} \longrightarrow \mathrm{Fe}^{2+} ; \quad E^{\circ}=0.77 \mathrm{~V}\)
\(\mathrm{O}_{2}+4 \mathrm{H}^{+}+4 e^{-} \longrightarrow 2 \mathrm{H}_{2} \mathrm{O} ; E^{\circ}=1.23 \mathrm{~V}\)
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Which of the following statements is correct?

(a) CI^- is oxidised by O₂ (b) Fe²⁺is oxidised by iodine

(c) I^- is oxidised by chlorine. (d) Mn²⁺ is oxidised by chlorine

(ii) Mn³⁺ is not stable in acidic medium, while Fe³⁺is stable because

(a) O₂ oxidises Mn²⁺ to Mn³⁺

(b) O₂ oxidises both Mn²⁺ to Mn³⁺ and Fe²⁺to Fe³⁺

(c) Fe^3-oxidises H₂O to O₂

(d) Mn³⁺ oxidises H₂O to O₂

(iii) The strongest reducing agent in the aqueous solution is

(a) I^- (b) Cl^- (c) Mn2⁺ (d) Fe²⁺

(iv) The emf for the following reaction is
\(\mathrm{I}_{2}+\mathrm{KCl} \rightleftharpoons 2 \mathrm{KI}+\mathrm{Cl}_{2}\)

(a) -0.82 V (b) +0.82 V (c) -0.73 V (d) +0.73 V
3)
Read the passage given below and answer the following questions :
All chemical reactions involve interaction of atoms and molecules. A large number of atoms/molecules are present in a few gram of any chemical compound varying with their atomic/molecular masses. To handle such large number conveniently, the mole concept was introduced. All electrochemical cell reactions are also based on mole concept. For example, a 4.0 molar aqueous solution of NaCI is prepared and 500 mL of this solution is electrolysed. This leads to the evolution of chlorine gas at one of the electrode. The amount of products formed can be calculated by using mole concept.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) The total number of moles of chlorine gas evolved is

(a) 0.5 (b) 1.0 (c) 1.5 (d) 1.9

(ii) If cathode is a Hg electrode, then the maximum weight of amalgam formed from this solution is

(a) 300 g (b) 446 g (c) 396 g (d) 296 g

(iii) In the electrolysis, the number of moles of electrons involved are

(a) 2 (b) 1 (c) 3 (d) 4

(iv) In electrolysis of aqueous NaCl solution when Pt electrode is taken, then which gas is liberated at cathode?

(a) H₂gas (b) C₂ gas (c) O₂ gas (d) None of these

4)

Read the passage given below and answer the following questions:
The concentration of potassium ions inside a biological cell is at least twenty times higher than the outside. The resulting potential difference across the cell is important in several processes such as transmission of nerve impulses and maintaining the ion balance. A simple model for such a concentration cell involving a metal M is M_(s) | M⁺(aq.; 0.05 molar) || M⁺(aq; 1 molar) |M_(s).
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) For the above cell,

(a) \(E_{\text {cell }}<0 ; \Delta G>0\)

(b) \(E_{\text {cell }}>0 ; \Delta G<0\)

(c) \(E_{\text {cell }}<0 ; \Delta G^{\circ}>0\)

(d) \(E_{\text {cell }}>0 ; \Delta G^{\circ}<0\)

(ii) The value of equilibrium constant for a feasible cell reaction is

(a) < 1

(b) = 1

(c) > 1

(d) zero

(iii) What is the emf ofthe cell when the cell reaction attains equilibrium?

(a) 1

(b) 0

(c) > 1

(d) < 1

(iv) The potential of an electrode change with change in

(a) concentration of ions in solution	(b) position of electrodes
(c) voltage of the cell	(d) all of these

5)
Read the passage given below and answer the following questions:
The electrochemical cell shown below is concentration cell. M|M²⁺ (saturated solution of a sparingly soluble salt, MX₂ ) || M²⁺ (0.001 mol dm^-3 ) | M The emf of the cell depends on the difference in concentrations of M²⁺ ions at the two electrodes. The emf of the cell at 298 K is 0.059 V.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The solubility product (K_sp, mol³ dm^-9) of MX₂ at 298 K based on the information available for the given concentration cell is (take 2.303 x R x 298/P = 0.059)

(a) 2 x 10^-15 (b) 4 x 10^-15 (c) 3 x 10^-12 (d) 1 x 10¹²

(ii) The value of \(\Delta G\) (in kJ mol^-1) for the given cell is (take 1F = 96500 C mol^-1)

(a) 3.7 (b) -3.7 (c) 10.5 (d) -11.4

(iii) The equilibrium constant for the following reaction is
\(\mathrm{Fe}^{2+}+\mathrm{Ce}^{4+} \rightleftharpoons \mathrm{Ce}^{3+}+\mathrm{Fe}^{3+}\)
(Given, \(E^{0} \mathrm{Ce}^{4+} / \mathrm{Ce}^{3+}=1.44\) and E^o \(E_{\mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}}=0.68 \mathrm{~V}\))

(a) 7.6 x 10¹² (b) 6.5 x 10¹⁰ (c) 5.2 x 10⁹ (d) 3.4 x 10¹²

(iv) To calculate the emf of the cell, which of the following options is correct?

(a) emf = E_cathode - E_anode (b) emf = E_anode - E_cathode

(c) emf = E_anode + E_cathode (d) None of these

CBSE 12th Standard Chemistry Subject Solution Case Study Questions With Solution 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
The concentration of a solute is very important in studying chemical reactions because it determines how often molecules collide in solution and thus indirectly determine the rate of reactions and the conditions at equilibrium.
There are several ways to express the amount of solute present in a solution. The concentration of a solution is a measure of the amount of solute that has been dissolved in a given amount of solvent or solution. Concentration can be expressed in terms of molarity, molality, parts per million, mass percentage, volume percentage, etc.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The molarity (in mol L^-1) of the given solution will be

(a) 1.56

(b) 1.89

(c) 0.263

(d) 1.44

(ii) Which of the following is correct relationship between mole fraction and molality?

\(\text { (a) } x_{2}=\frac{m M_{1}}{1+m M_{1}}\)	\(\text { (b) } x_{2}=\frac{m M_{1}}{1-m M_{1}}\)
\(\text { (c) } x_{2}=\frac{1+m M_{1}}{m M_{1}}\)	\(\text { (d) } x_{2}=\frac{1-m M_{1}}{m M_{1}}\)

(iii) Which of the following is temperature dependent?

(a) Molarity	(b) Molality
(c) Mole fraction	(d) Mass percentage

(iv) Which of the following is true for an aqueous solution of the solute in terms of concentration?

(a) 1 M = 1 m	(b) 1M > 1m
(c) 1M < 1 m	(d) Cannot be predicted

2)
Read the passage given below and answer the following questions:
At 298 K, the vapour pressure of pure benzene, C₆H₆ is 0.256 bar and the vapour pressure of pure toluene
C₆H₅CH₃ is 0.0925 bar. Two mixtures were prepared as follows:
(i) 7.8 g of C₆H₆ + 9.2 g of toluene
(ii) 3.9 g of C₆H₆ + 13.8 g of toluene
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The total vapour pressure (bar) of solution 1 is

(a) 0.128 (b) 0.174 (c) 0.198 (d) 0.258

(ii) Which of the given solutions have higher vapour pressure?

(a) I (b) II

(c) Both have equal vapour pressure (d) Cannot be predicted

(iii) Mole fraction of benzene in vapour phase in solution 1 is

(a) 0.128 (b) 0.174 (c) 0.734 (d) 0.266

(iv) Solution I is an example of a/an

(a) ideal solution (b) non-ideal solution with positive deviation

(c) non-ideal solution with negative deviation (d) can't be predicted

3)

Read the passage given below and answer the following questions:
An ideal solution may be defined as the solution which obeys Raoult's law exactly over the entire range of concentration. The solutions for which vapour pressure is either higher or lower than that predicted by Raoult's law are called non-ideal solutions.
Non-ideal solutions can show either positive or negative deviations from Raoult's law depending on whether the A-B interactions in solution are stronger or weaker than A - A and B - B interactions.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Which of the following solutions is/are ideal solution(s)?
(i) Bromoethane and iodoethane (ii) Acetone and chloroform
(iii) Benzene and acetone (iv)n-heptane and n-hexane

(a) only 1

(b) I and II

(c) II and III

(d) I and IV

(ii) Which of the following is not true for positive deviations?

(a) The A-B interactions in solution are weaker than the A -A and B -B interactions.

(b) \(P_{A}<P_{A}^{\circ} x_{A} \text { and } P_{B}<P_{B}^{\circ} x_{B}\)

(c) Carbon tetrachloride and chloroform mixture is an example of positive deviations.

(d) All of these

(iii) For water and nitric acid mixture which of the given graph is correct?


(C) Both of these	(d) None of these

(iv) Water- HCl mixture
I. shows positive deviations II. forms minimum boiling azeotrope
III. shows negative deviations IV. forms maximum boiling azeotrope

(a) I and II	(b) II and III
(c) I and IV	(d) III and IV

4)
Read the passage given below and answer the following questions:
The properties of the solutions which depend only on the number of solute particles but not on the nature of the solute are called colligative properties. Relative lowering in vapour pressure is also an example of colligative properties.
For an experiment, sugar solution is prepared for which lowering in vapour pressure was found to be 0.061 mm of Hg. (Vapour pressure of water at 20°C is 17.5 mm of Hg.)
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Relative lowering of vapour pressure for the given solution is

(a) 0.00348 (b) 0.061 (c) 0.122 (d) 1.75

(ii) The vapour pressure (mm of Hg) of solution will be

(a) 17.5 (b) 0.61 (c) 17.439 (d) 0.00348

(iii) Mole fraction of sugar in the solution is

(a) 0.00348 (b) 0.9965 (c) 0.061 (d) 1.75

(iv) The vapour pressure (mm of Hg) of water at 293 K when 25 g of glucose is dissolved in 450 g of water is

(a) 17.2 (b) 17.4 (c) 17.120 (d) 17.02
5)
Read the passage given below and answer the following questions:
Few colligative properties are:
(a) relative lowering of vapour pressure: depends only on molar concentration of solute (mole fraction) and independent of its nature.
(b) depression in freezing point: it is proportional to the molal concentration of solution.
(c) elevation of boiling point: it is proportional to the molal concentration of solute.
(d) osmotic pressure: it is proportional to the molar concentration of solute.
A solution of glucose is prepared with 0.052 g at glucose in 80.2 g of water. (K_f = 1.86 K kg mol^-1 and K_b = 5.2 K kg mol^-1)
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Molality of the given solution is

(a) 0.0052 m (b) 0.0036 m (c) 0.0006 m (d) 1.29 m

(ii) Boiling point for the solution will be

(a) 373.05 K (b) 373.15 K (c) 373.02 K (d) 372.98 K

(iii) The depression in freezing point of solution will be

(a) 0.0187 K (b) 0.035 K (c) 0.082 K (d) 0.067 K

(iv) Mole fraction of glucose in the given solution is

(a) 6.28 x 10^-5 (b) 1.23 x 10^-4 (c) 0.00625 (b) 0.00028

CBSE 12th Standard Chemistry Subject The Solid State Case Study Questions With Solution 2021 - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)

Read the passage given below and answer the following questions:
The adjective, 'crystalline' when applied to solids, implies an ideal crystal in which the structural units, termed as unit cells, are repeated regularly and indefinitely in three dimensions in space. The unit cell, containing at least one molecule, has a definite orientation and shape defined by the translational vectors, a, band c. The unit cell therefore has a definite volume, V that contains the atoms and molecules necessary for generating the crystal. Every crystal can be classified as a member of one of the seven possible crystal systems or crystal classes that are defined by the relationships between the individual dimensions, a, band c of the unit cell and between the individual angles, \(\alpha, \beta \ and \ \gamma\) of the unit cell. The structure of the given crystal may be assigned to one of the 7 crystal systems, to one of the 14 Bravais lattices, and to one of the 230 space groups. These uniquely define the possible ways of arranging atoms in a three-dimensional solid. Based on these observations, seven crystal systems were identified: triclinic, monoclinic, trigonal or rhombohedral, tetragonal, hexagonal, rhombic or orthorhombic and cubic.
The following questions are multiple choice questions. Choose the most appropriate answer :
(i) The crystal system of a compound with unit cell dimensions, a = 0.387 nm, b = 0.387 nm and c = 0.504 nm and \(\alpha, \beta \ =90^o\) and \(\gamma\) = 120° is

(a) cubic

(b) hexagonal

(c) orthorhombic

(d) rhombohedral.

(ii) The unit cell with the structure given below represents __________crystal system.

a) cubic

(b) orthorhombic

(c) tetragonal

(d) trigonal

(iii) In a triclinic crystal

\(\text { (a) } a=b=c, \quad \alpha=\beta=\gamma \neq 90^{\circ}\)	\(\text { (b) } a \neq b=c, \quad \alpha=\beta=\gamma=90^{\circ}\)
\(\text { (c) } a \neq b \neq c, \quad \alpha \neq \beta \neq \gamma \neq 90^{\circ}\)	\(\text { (d) } a \neq b \neq c, \quad \alpha=\gamma=90^{\circ}, \beta \neq 90^{\circ}\)

(iv) The unit cell with dimensions \(\alpha=\beta=\gamma=90^{\circ}, a=b \neq c \) is

(a) cubic

(b) triclinic

(c) hexagonal

(d) tetragonal

2)
Read the passage given below and answer the following questions:
In contrast to the disorders of gases and liquids, there is translational order in crystals. However, disordered or amorphous solids also exist which lack such order, they are really highly viscous liquids. In translational order entire structure or lattice, can be generated by repeated replication of a small regular figure, termed as unit cell. The planes of any crystalline structure can be specified using Miller indices, which is also serve to identify single crystal faces.
The ordered structure or lattice, of a solid can be determined by X-ray or neutron diffraction studies, in which a beam of X-rays of neutrons is scattered from the sample to produce a diffraction pattern which can be analyzed to reveal the crystal structure of the sample. All crystal lattices can be classified into 14 Bravais lattices belonging to 7 systems. For example, the simple cubic, face-centred cubic and body-centred cubic lattices are the 3 lattices of the cubic system. Cubic and hexagonal close- packed structures have the structure of tightly packed spheres where each sphere touches 12 neighbours, 6 in the same plane and 3 above and 3 below. These two close-packed structures differ in the placement of successive planes or layers. For the hexagonal close packing, a third layer is laid down to reproduce the first layer, so that the structure could be represented by ABABAB .... For cubic close packing, third layer is again displaced, corn spending to ABCABC ...
The following questions are multiple choice questions. Choose the most a propriate answer:
(i) In hexagonal close packing, a sphere has coordination number of

(a) 4 (b) 6 (c) 8 (d) 12

(ii) Which of the following arrangements correctly represents hexagonal and cubic close packed structure respectively?

(a) ABCABC .. and ABAB ... (b) ABAB ... and ABCABC ..

(c) Both have ABAB ... arrangement. (d) Both have ABCABC .. arrangement

(iii) The arrangement of the first two layers, one above the other in hep and eep arrangements is

(a) exactly same in both cases (b) partly same and partly different

(c) different from each other (d) nothing definite

(iv) Which of the following statements about amorphous solids is incorrect?

(a) They melt over a range of temperature.

(b) There is no orderly arrangement of particles.

(c) They are anisotropic

(d) They are rigid and incompressible.

3)

Read the passage given below and answer the following questions:
In ideally ionic structures, the coordination numbers of the ions are determined by electrostatic considerations. Cations surround themselves with as many anions as possible and vice versa. This maximizes the attractions between neighbouring ions of opposite charge and hence maximizes the lattice energy of the crystal. This requirement led to the formulation of the radius ratio rule for ionic structures in which the ions and the structure adopted for a particular compound depend on the relative sizes of the ions. Thus, for the stable ionic crystalline structures, there is definite radius ratio limit for a cation to fit perfectly in the lattice of anions, called radius ratio rule. This depends upon the ratio of radii of two types of ions, r₊/r_-.
This ratio for coordination numbers 3, 4, 6 and 8 are respectively 0.155 - 0.225, 0.225 - 0.414, 0.414 - 0.732 and 0.732 - 1.000. The coordination number of ionic solids also depends upon temperature and pressure. On applying high pressure, coordination number increases. On the other hand, on applying high temperature, it decreases.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) The ionic radii of K⁺, Rb⁺ and Br^-are 137, 148 and 195 pm. The coordination number of cation in RbBr and KBr structures are respectively

(a) 8,6

(b) 6,4

(c) 6,8

(d) 4,6

(ii) If the radius of Na⁺ion is 95 pm and that of Cl^-ion is 181 pm, the coordination number of Na⁺ion is

(a) 6

(b) 4

(c) 8

(d) 12

(iii) Which is not the correct statement for ionic solids in which positive and negative ions are held by strong electrostatic attractive forces?

(a) The radius ratio r₊/r_- increases as coordination number increases

(b) As the difference in size of ions increases, coordination number increases.

(c) When coordination number is eight, r₊/r_- ratio lies between 0.225 to 0.414

(d) In ionic solid of the type AX (ZnS, wurtzite), the coordination number of Zn²⁺ and S^2- respectively are 4 and 4

(iv) If the pressure of CsCl is increased, then its coordination number will

(a) increase

(b) remain the same

(c) decrease

(d) none of these

4)

Read the passage given below and answer the following questions:
In an ideal crystal, there must be regular repeating arrangement of the constituting particles and its entropy must be zero at absolute zero temperature. However, it is impossible to obtain an ideal crystal and it suffers from certain defects called imperfections. In pure crystal, these defects arises either due to disorder or dislocation of the constituting particles from their normal positions or due to the movement of the particles even at absolute zero temperature. Such defects increase with rise in temperature. In addition to this, certain defects arise due to the presence of some impurities. Such defects not only modify the existing properties of the crystalline solids but also impart certain new characteristics to them.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) AgCI is crystallized from molten AgCI containing a little CdCI₂. The solid obtained will have

(a) cationic vacancies equal to number of Cd²⁺ ions incorporated

(b) cationic vacancies equal to double the number of Cd²⁺ ions

(c) anionic vacancies

(d) neither cationic nor anionic vacancies.

(ii)The ionic substances in which the cation and anion are of almost similar size shows

(a) non-stoichiometric defect	(b) Schottky defect
(c) Frenkel defect	(d) all of these.

(iii) If A1³⁺ions replace Na⁺ ions at the edge centres of NaCl lattice, then the number of vacancies in 1mole of NaCI will be

(a) 3.01 x 10²³

(b) 6.02 x 10²³

(c) 9.03 x 10²³

(d) 12.04 x 10²³

(iv) Which of the following gives both Frenkel and Schottky defect?

(a) AgCl

(b) CsCI

(c) KCI

(d) AgBr

5)

Read the passage given below and answer the following questions:
The idealized ionic solid consists of two interpenetrating lattices of oppositely-charged point charges that are held in place by a balance of coulombic force of long range. But real ions occupy space, no such "perfect" ionic solid exists in nature. Chemists usually apply the term "ionic solid" to binary compounds of the metallic elements of groups 1 - 2 with one of the halogen elements or oxygen. The most well known ionic solid is sodium chloride, also known by its geological names as rock-salt or halite. Structurally, each ion in sodium chloride is surrounded and held in tension by six neighbouring ions of opposite charge; this is known as (6, 6) coordination. The resulting crystal lattice is of a type known as simple cubic. There are many other fundamental ionic structures (not all cubic) and these are:
Zinc blende structure (ZnS) : having ccp arrangement of S^2- and Zn²⁺ in alternate tetrahedral voids; Wurtzite structure (ZnS) : having hcp arrangement of S^2- and Zn²⁺in alternate tetrahedral voids; Fluorite structure (CaF₂) : having ccp arrangement of Ca²⁺ and F^- in all tetrahedral voids; Antifluorite structure (Na₂O): having ccp arrangement of O^2- and Na⁺ in all tetrahedral voids. These solids tend to be quite hard and have high melting points.
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) In NaCl crystal, each Cl^- ion is surrounded by

(a) 4 Na⁺ions

(b) 6 Na⁺ions

(c) 1Na⁺ion

(d) 2 Na⁺ions.

(ii) In an antifluorite structure, cations occupy

(a) tetrahedral voids

(b) centre of cube

(c) octahedral voids

(d) corners of cube

(iii) Antifluorite structure is derived from fluorite structure by

(a) heating fluorite crystal lattice

(b) subjecting fluorite structure to high pressure

(c) interchanging the positions of positive and negative ions in the lattice

(d) none of these.

(iv) Ionic solid BaF₂ has which kind of structure?

(a) Fluorite

(b) Antifluorite

(c) Wurtzite

(d) Rock-salt

CBSE 12th Standard Chemistry Subject Case Study Questions With Solution 2021 Part - I - by Archana Singh - Deoghar - May 21, 2021 - View & Read

1)
Read the passage given below and answer the following questions:
Most important crystal lattices are the simple cubic, body centred cubic and face centred cubic. In simple cubic lattice, all the atoms are present at all the corners of the cube. In body-centred cubic lattice, atoms are present at all the corners and at the body-centre. In face-centred cubic lattice, atoms are present at the corners and at the centers of all' six faces.
In the formation of crystals, the constituent particles get closely packed together. The closely packed arrangement is that in which maximum available space is occupied leaving minimum vacant space. The most efficient close packing, can be achieved in two ways, one which is called hexagonal close packing (hcp) and the other, cubic close packing (ccp or fcc).
In these questions (i-iv), a statement of assertion followed by a statement of reason is given. Choose the correct answer out of the following choices.
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.
(i) Assertion: Face centred cubic cell has 4 atoms per unit cell.
Reason: In fcc unit cell, there are 8 atoms at the corners and 6 atoms at face centres.
(ii) Assertion: fee and hep have same packing efficiency.
Reason: bee and fee both have same number of atoms per unit cell and same arrangement.
(iii) Assertion: The total number of atoms present in a simple cubic unit cell is one.
Reason: Simple cubic unit cell has atoms at its corners, each of which is shared between eight adjacent unit cells.
(iv) Assertion: The packing efficiency is maximum for the fccstructure.
Reason: The coordination number is 12 in fcc structures.
2)
Read the passage given below and answer the following questions:
Few colligative properties are:
(a) relative lowering of vapour pressure: depends only on molar concentration of solute (mole fraction) and independent of its nature.
(b) depression in freezing point: it is proportional to the molal concentration of solution.
(c) elevation of boiling point: it is proportional to the molal concentration of solute.
(d) osmotic pressure: it is proportional to the molar concentration of solute.
A solution of glucose is prepared with 0.052 g at glucose in 80.2 g of water. (K_f = 1.86 K kg mol^-1 and K_b = 5.2 K kg mol^-1)
The following questions are multiple choice questions. Choose the most appropriate answer:
(i) Molality of the given solution is

(a) 0.0052 m (b) 0.0036 m (c) 0.0006 m (d) 1.29 m

(ii) Boiling point for the solution will be

(a) 373.05 K (b) 373.15 K (c) 373.02 K (d) 372.98 K

(iii) The depression in freezing point of solution will be

(a) 0.0187 K (b) 0.035 K (c) 0.082 K (d) 0.067 K

(iv) Mole fraction of glucose in the given solution is

(a) 6.28 x 10^-5 (b) 1.23 x 10^-4 (c) 0.00625 (b) 0.00028