10th Standard CBSE Science CBSE - study material, free online tests, previous year question papers, answer keys, topper answers, centum question paper, exam tips

CBSE 10th Science Metals And Non Metals Chapter Case Study Question with Answers - by users_admin - Jan 06, 2024 - View & Read

CBSE 10th Science Acids, Bases And Salts Chapter Case Study Question with Answers - by users_admin - Jan 06, 2024 - View & Read

CBSE 10th Science Chemical Reactions And Equations Chapter Case Study Question with Answers - by users_admin - Jan 06, 2024 - View & Read

CBSE 10th Standard Science Subject Chemical Reactions and Equations HOT Questions 3 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
Give six uses of decomposition reaction.
2)
Mohan took pure water for the electrolytic decomposition of water but did not see any bubble near the electrodes. Explain why?
3)
A teacher took few crystals of sugar in a dry test tube and heated the test tube over flame. The colour of sugar turned black. Explain why?
4)
Blue crystals of copper sulphate on heating in a dry test tube become colourless. Give reasons.
5)
FeSO₄.7H₂O, green colour crystals on heating, changes colour. Why?

CBSE 10th Standard Science Subject Our Environment HOT Questions 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
If a harmful chemical enters a food chain consisting of snacks, grasshoppers, plants and frogs, which one of the organisms is likely to have a maximum concentration of harmful chemicals in its body?
2)
A food chain consisting of Peacock, Frog, Snake, Grasshopper. Which organisms do you think will have high level of pesticides? What is the phenomenon called? Arrange the food chain.
3)
In comparing two ecosystems 'X' and 'Y', i is observed that 'X' has only first and second order consumers, while 'Y' has third, fourth and fifth order consumers. Which of the two would be more stable?
4)
In the food chain given below:
Grass\(\longrightarrow\)Grasshopper\(\longrightarrow\)Frog\(\longrightarrow\)Snake\(\longrightarrow\)Peacock
What will happen if all the frogs are removed?
5)
A non-biodegradable toxic chemical has entered into the food chain. Which type of food habit will you suggest, vegetarian or non-vegetarian? Why?

CBSE 10th Standard Science Subject Sources of Energy HOT Questions 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
Hydrogen compounds are abundantly available on earth and it has high calorific values. But this is not used as a common fuel. Give any two reasons. What are being developed to use hydrogen as a common fuel?
2)
Why does a car parked in sunlight remains hot from inside even when there is no sunlight in the car?
3)
Energy can neither be created nor destroyed. Then why is there so must about energy crisis?
4)
Describe the areas where acids are most likely expected?
5)
It is said that a differences of 20^o C in temperature of water at two levels can be exploited to generate electricity. Name the plant that can be used for this purpose. Describe the process and give its main advantages

CBSE 10th Standard Science Subject Human Eye and the Colourful World HOT Questions 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
Does myopia or hypermetropia imply necessary that the eye has partially lost its ability of accommodation?If not, what cause these defect of vision?
2)
A person has normal vision, but he cannot distinguish between red-green colour.Why?
3)
Mention few important features of visual system of a person?
4)
To correct myopia why we use concave lens and to correct hypermetropia, why do we use convex lens? Why can't we do vice-versa?

CBSE 10th Standard Science Subject Light Reflection and Refraction HOT Questions 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
Why do we prefer a convex mirror as a rear view mirror in vehicles?
2)
Find the focal length of a lens of power - 2 D. What type of lens is this?
3)
How do you find the rough focal length of a convex lens? Is the same method applicable to a concave lens?
4)
What are the factors that determine the focal length of a lens?
5)
Does the method to find the approximate focal length of a convex lens is applicable to concave lens?

CBSE 10th Standard Science Subject Heredity and Evolution HOT Questions 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
A new born has an XX pair of chromosomes. What is the sex of the new born baby?
2)
What will be the colour of the hair of a person if he inherits a gene for red hair from his mother and a gene for black hair from his father provided the gene for red hair is recessive to the gene for black hair?
3)
What is the genotype of dwarf plants whose parental cross always produced tall offspring?
4)
In F₂ generation, progeny having different traits are produced in the ratio of 3 : 1. Is it a monohybrid cross or dihybrid cross?
5)
If a normal human cell has 46 chromosomes, then how many chromosomes will be there in a human zygote?

CBSE 10th Standard Science Subject Periodic Classification of Elements HOT Questions 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
Predict the group of an element A if its atomic number is 16.
2)
What is the probable formula of the oxide of the Silicon?
3)
If an element is in group 7 or VIIA, is it likely to be metallic or non-metallic nature?
4)
An element A belongs to group II and another element B belongs to group 15 of the periodic table.
(a) What is the number of valence electrons in A and B?
(b) What is the valency of A and B?
5)
The atomic number of three elements X, Y and Z are 5, 7 and 10 respectively.
(a) Which element belongs to group IIIA?
(b) To which period do these elements belong?
(c) Which element belongs to VA?
(d) Which element belongs to zero group?

CBSE 10th Standard Science Subject Life Processes HOT Questions 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
What do the following transport?
(a)Xylem
(b)Phloem
(c)Pulmonary vein
(d)Pulmonary artery
2)
Three organisms ate food in the form of glucose and the end products after respiration are:
a - ethanol + CO₂
b - CO₂+H₂O
c - Lactic acid + water
Explain how is this possible?
3)
Name the following in human system:
(i) Balloon like structures richly supplied with blood capillaries.
(ii) Prevents the back flow of blood in heart.
(iii) squeeze out the water with amino acids and other wastes and separates from the blood.
(iv) Bring impure blood to kidney.
(v) Rythmic contraction and relaxation of walls of digestive system
4)
Name the excretory wastes of the following:
(a) Digestive systems
(b) Kidney
(c) Skin
(d) Lungs
(e) Plants stem
(f) Leaves
5)
Give the role of the following in plants and animals:
(a) Guard cells
(b) Tracheids and vessels
(c) Lymph
(d) Phloem
(e) Bio-catalyst

CBSE 10th Standard Science Subject Life Processes HOT Questions 2 Mark Questions 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
How the process of digestion will be affected if the bile ducts get blocked?
2)
(a)What prevents the entry of food into trachea while swallowing?
(b)Why rate of breathing is faster in aquatic animals as compared to terrestrial animals?
3)
What do the following transport?
(a)Xylem
(b)Phloem
(c)Pulmonary vein
(d)Pulmonary artery
4)
a - What is this structure called and give its state-open or closed?
b - Where are they present?
c - What controls the opening and closing of it?
d - Draw the opposite figure to this.
5)
Three organisms ate food in the form of glucose and the end products after respiration are:
a - ethanol + CO₂
b - CO₂+H₂O
c - Lactic acid + water
Explain how is this possible?

CBSE 10th Standard Science Subject Carbon and Its Compounds HOT Questions 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
A, B, C are members of homologous series and their melting points are -183°C, -138°C, 130°C respectively. Among these
(i) Which member will have least number of carbon atoms?
(ii) Which member will have maximum number of carbon atoms?
2)
A hydrocarbon compound A is active ingredient of wine and cough syrup. A on oxidation with acidified K₂Cr₂O₇ forms compound B. Identify the compound A and B and write the chemical equations involved.
3)
Write an activity to show the acidic nature of ethanol. Give the chemical equation of the reaction taking place
4)
A compound 'X' has molecular formula C2H60 is saturated hydrocarbons and is a very good solvent. How can you convert it into unsaturated hydrocarbon? Identify X and show its conversion with the help of equation.
5)
Take about 20 mL of castor oil in a beaker. Add 30 mL of 20% sodium hydroxide solution. Heat the mixture with continuous stirring for a few minutes till the mixture thickens. Add 5-10 g of common salt to this. Stir the mixture well, allow it to cool, soaps is obtained.

(a) Why do we use common salt to make soap?
(b) What will happen if you will add the above made soap solutions to the following test tubes A, B, and C.
(c) Can we use potassium hydroxide instead of sodium hydroxide.

CBSE 10th Standard Science Subject Carbon and Its Compounds HOT Questions 2 Mark Questions 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
Which of the following compounds contain a carboxyl group?
CH₃OH, CH₃COOH, CH₃CHO, CH₃COCH₃
2)
An organic compound 'A' which is used as antifreeze has the molecular formula C₂H₆O. On addition, it gives a compound 'B' which baking soda solution. Identify the compound A and B.
3)
An organic compound 'X' is a constituent of wine and beer. The compound X on heating with potassium dichromate forms another organic compound 'Y'. Identify the compound X and Y.
4)
How will you convert ethanol to ethene?
5)
A, B, C are members of homologous series and their melting points are -183°C, -138°C, 130°C respectively. Among these
(i) Which member will have least number of carbon atoms?
(ii) Which member will have maximum number of carbon atoms?

CBSE 10th Standard Science Subject Chemical Reactions and Equations HOT Questions 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
A yellowish coloured compound 'A' is photosensitive material. On exposure to sunlight, it gives a greyish substance 'B' and brown fumes of a gas 'C'. Identify A, B and C. How will you obtain A from the nitrate salt of B?
2)
A substance 'A' displaces 'B' from its solution in water. It is called displacement reaction. What other chemical name can be given to such type of reactions? Explain with an example.
3)
In the reaction:
2KClO₃ \(\overset { \Delta/MnO_2 }{ \rightarrow } \) 2KCl + 3O₂, what does the '\(\Delta\)' and 'MnO₂' signify? What type of reaction is this?
4)
A metal X available in the form of ribbon burns in air with a dazzling white light once heated to its ignition temperature. It leaves a white powder Y which dissolves in water. The solution so formed turns red litmus blue. Identify X and Y and write a balanced chemical equation of the reaction.
(a) Identify 'X' and 'Y'.
(b) Write a balanced chemical equation for this reaction.
5)
A pinch of solid sodium carbonate is added into dilute hydrochloric acid in a test tube. Sodium chloride and water formed remains the solution whereas the carbon dioxide escapes out. The tube found to become hot.
(a) Represent it in word equation.
(b) Give the formula of the word equation.
(c) Balance the equation.
(d) How will the reaction be represented to make it maximum informative?

CBSE 10th Standard Science Subject Chemical Reactions and Equations HOT Questions 2 Mark Questions 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
A metal X available in the form of ribbon burns in air with a dazzling white light once heated to its ignition temperature. It leaves a white powder Y which dissolves in water. The solution so formed turns red litmus blue. Identify X and Y and write a balanced chemical equation of the reaction.
(a) Identify 'X' and 'Y'.
(b) Write a balanced chemical equation for this reaction.
2)
List four changes which help us to determine whether a chemical reaction has taken place
3)
Give one example of a combination reaction in which an element combines with a compound to give you a new compound
4)
Give two examples in which reactants react to show combination reaction and a new product is formed. This new product decomposes to give the initial reactants.
\( \text { e.g., } X+Y \stackrel{\text { combination }}{\longrightarrow} Z \ \ \ \ \ Z \stackrel{\text { decomposition }}{\longrightarrow} X+Y \)
5)
Why are certain reagents like silver bromide stored in dark bottles in the labs?

CBSE 10th Standard Science Subject Control and Coordination HOT Questions 1 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
Name the stress and fear hormones.
2)
Give the names of hormones responsible for the physical changes in a boy and girl
3)
Name the element of halogen family required for the proper functioning of thyroid gland.
4)
A doctor advised a patient to take less sugar in her diet. Which disease is she suffering from?
5)
Name the receptors of light, sound, smell and taste

CBSE 10th Standard Science Subject Control and Coordination HOT Questions 1 Mark Questions 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
A patient is not able to balance his body and cannot walk properly by keeping the balance and cannot coordinate it. Name the part of brain which is affected.
2)
Name the hormone that controls the rate of respiration, also name the part of brain responsible for controlling respiration.
3)
Doctor advised a patient to take iodised salt. Explain why?
4)
What are the limitations of electrical impulse?
5)
If there is no neuron in an organ, how will the message reach in other way?

CBSE 10th Standard Science Subject Light Reflection and Refraction HOT Questions 1 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
What are the two types of reflection?
2)
Give characteristics of image formed by plane mirror
3)
Give uses of plane mirror.
4)
Name two types of spherical mirror
5)
An incident ray makes an angle of 60° with the mirror. What is the angle of reflection?

CBSE 10th Standard Science Subject Light Reflection and Refraction HOT Questions 1 Mark Questions 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
Give uses of concave mirror.
2)
Give uses of convex mirrors
3)
Amit visited a fair and saw a mirror in which he got a very funny image. The above part of his body was big in size, middle part was of normal size and the lower part of the body showed very small size. What kind of mirror is this?
4)
Nidhi wanted the image of her pencil to be double the size of its original size. Name the mirror used for getting such image
5)
Give the mirror image of 'AMBULANCE"

CBSE 10th Standard Science Subject Chemical Reactions and Equations HOT Questions 1 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
A compound ‘X’ is used for drinking has pH=7. Its acidified solution in presence of electricity undergoes decomposition to produce gases ‘Y’ and ’Z’. The volume of ‘Y’ is double than ‘Z’.’Y’ is highly combustible where as ‘Z’ is a supporter of combustion. Identify ‘X,’Y, ’Z’and write the chemical reactions involved.
2)
A metal nitrate solution ‘A’ is added to reddish brown metal ‘B’. The metal present in ‘A’ is used for making jewellery and turns black in air, very thin foils of metal are used to decorate sweets. The compound ‘C’ formed on chemical reaction is blue in color and metal present in ‘A’ is formed. Identify A’ ‘B’ and ‘C’ and write chemical reactions involved.
3)
Silver articles develop black coating and copper articles develop green coating. Which chemical phenomenon is responsible for this coating?
4)
An aqueous solution of metal nitrate ‘X’ reacts with Sodium bromide solution to form yellow precipitate of compound ‘Y’ which is used in photography. ‘Y’ on exposure to sunlight, undergoes decomposition reaction to form metal present in ‘X’ along with gas. Identify ‘X’ and ‘Y’. Write the chemical reaction and identify the type of reaction.
5)
Name the term used for the solution of the reactant or product when dissolved in water.

CBSE 10th Standard Science Subject Chemical Reactions and Equations HOT Questions 1 Mark Questions 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
What happens to idli dough when it is kept at room temperature on a summer day?
2)
People living in coastal areas use plastic articles than iron articles for their day to day activities. Why?
3)
The decomposition of vegetable matter in to compost is an example of what type of reaction?
4)
Which term is used to indicate the development of unpleasant smell and taste in butter and oil containing food?
5)
Ashok wanted his house to white washed. He bought 10kg quick lime from market and dissolved it in 30 liters of water. On adding lime to water he noticed that bubbles were produced and the solution becomes hot. Give reason and name the product formed.

CBSE 10th Standard Science Subject HOT Questions 3 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
State one advantage and one disadvantage of corrosion
2)
Ahmad took a magnesium ribbon (cleaned) and burned it on a flame. The white powder formed was taken in a test tube and water was added to it. He then tested the solution formed with red and blue litmus paper. What change was seen and why?
3)
Arnav took magnesium and reacted it with dil. HCI to record the observation. Then Deepak took the same piece of magnesium and reacted it with conc. HNO₃ and dil. H2SO₄ but did not see a reaction. Explain this behavior.
4)
Four beakers with chemicals are shown below. Name the beakers which will show exothermic reaction and those which will be endothermic in nature.
5)
Blue crystals of copper sulphate on heating in a dry test tube become colourless. Give reasons.

CBSE 10th Standard Science Subject HOT Questions 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
A substance 'A' displaces 'B' from its solution in water. It is called displacement reaction. What other chemical name can be given to such type of reactions? Explain with an example.
2)
In the reaction:
2KClO₃ \(\overset { \Delta/MnO_2 }{ \rightarrow } \) 2KCl + 3O₂, what does the '\(\Delta\)' and 'MnO₂' signify? What type of reaction is this?
3)
Give two examples in which reactants react to show combination reaction and a new product is formed. This new product decomposes to give the initial reactants.
\( \text { e.g., } X+Y \stackrel{\text { combination }}{\longrightarrow} Z \ \ \ \ \ Z \stackrel{\text { decomposition }}{\longrightarrow} X+Y \)
4)
Which of the following compounds contain a carboxyl group?
CH₃OH, CH₃COOH, CH₃CHO, CH₃COCH₃
5)
A hydrocarbon compound A is active ingredient of wine and cough syrup. A on oxidation with acidified K₂Cr₂O₇ forms compound B. Identify the compound A and B and write the chemical equations involved.

CBSE 10th Standard Science Subject HOT Questions 2 Mark Questions 2021 Part - II - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
A substance 'A' displaces 'B' from its solution in water. It is called displacement reaction. What other chemical name can be given to such type of reactions? Explain with an example.
2)
List four changes which help us to determine whether a chemical reaction has taken place
3)
An organic compound 'A' which is used as antifreeze has the molecular formula C₂H₆O. On addition, it gives a compound 'B' which baking soda solution. Identify the compound A and B.
4)
A hydrocarbon compound A is active ingredient of wine and cough syrup. A on oxidation with acidified K₂Cr₂O₇ forms compound B. Identify the compound A and B and write the chemical equations involved.
5)
Take about 20 mL of castor oil in a beaker. Add 30 mL of 20% sodium hydroxide solution. Heat the mixture with continuous stirring for a few minutes till the mixture thickens. Add 5-10 g of common salt to this. Stir the mixture well, allow it to cool, soaps is obtained.

(a) Why do we use common salt to make soap?
(b) What will happen if you will add the above made soap solutions to the following test tubes A, B, and C.
(c) Can we use potassium hydroxide instead of sodium hydroxide.

CBSE 10th Standard Science Subject HOT Questions 2 Mark Questions 2021 Part - I - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
a - What is this structure called and give its state-open or closed?
b - Where are they present?
c - What controls the opening and closing of it?
d - Draw the opposite figure to this.
2)
(a)Is variations beneficial to the species?
(b)If yes, give reason.
(c)Is variation necessary for the individuals?Why?
3)
Does genetic combination of mother play a significant role in determining the sex of new born baby?
4)
What are the factors that determine the focal length of a lens?
5)
A person has normal vision, but he cannot distinguish between red-green colour.Why?

CBSE 10th Standard Science Subject HOT Questions 1 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
Arun took a pale green substance X in a test tube, and heated it over a flame. He observed a color change along with evolution of two gases with the smell of burning sulphur
(a) Identify X.
(b) Identify the product formed.
(c) Write the equation.
(d) Identify the type of chemical reaction.
2)
A compound ‘X’ is used for drinking has pH=7. Its acidified solution in presence of electricity undergoes decomposition to produce gases ‘Y’ and ’Z’. The volume of ‘Y’ is double than ‘Z’.’Y’ is highly combustible where as ‘Z’ is a supporter of combustion. Identify ‘X,’Y, ’Z’and write the chemical reactions involved.
3)
Name the term used for the solution of the reactant or product when dissolved in water.
4)
A compound ‘X’ is an important ingredient of an antacid. It is also used in fire extinguisher. Identify ‘X’.
5)
Name the element of halogen family required for the proper functioning of thyroid gland.

CBSE 10th Standard Science Subject HOT Questions 1 Mark Questions 2021 Part - II - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
What happens to idli dough when it is kept at room temperature on a summer day?
2)
People living in coastal areas use plastic articles than iron articles for their day to day activities. Why?
3)
An aqueous solution of metal nitrate ‘X’ reacts with Sodium bromide solution to form yellow precipitate of compound ‘Y’ which is used in photography. ‘Y’ on exposure to sunlight, undergoes decomposition reaction to form metal present in ‘X’ along with gas. Identify ‘X’ and ‘Y’. Write the chemical reaction and identify the type of reaction.
4)
A doctor advised a patient to take less sugar in her diet. Which disease is she suffering from?
5)
Name the receptors of light, sound, smell and taste

CBSE 10th Standard Science Subject HOT Questions 1 Mark Questions 2021 Part - I - by Prerna - Bangalore - May 29, 2021 - View & Read

1)
People living in coastal areas use plastic articles than iron articles for their day to day activities. Why?
2)
Arun took a pale green substance X in a test tube, and heated it over a flame. He observed a color change along with evolution of two gases with the smell of burning sulphur
(a) Identify X.
(b) Identify the product formed.
(c) Write the equation.
(d) Identify the type of chemical reaction.
3)
A metal nitrate solution ‘A’ is added to reddish brown metal ‘B’. The metal present in ‘A’ is used for making jewellery and turns black in air, very thin foils of metal are used to decorate sweets. The compound ‘C’ formed on chemical reaction is blue in color and metal present in ‘A’ is formed. Identify A’ ‘B’ and ‘C’ and write chemical reactions involved.
4)
A doctor advised a patient to take less sugar in her diet. Which disease is she suffering from?
5)
A patient is not able to balance his body and cannot walk properly by keeping the balance and cannot coordinate it. Name the part of brain which is affected.

CBSE 10th Standard Science Subject Sustainable Management of Natural Resources Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
In the context of conservation of natural resources, explain the terms reduce, recycle and reuse. From among the materials that we use in daily life, identify two materials for each category.
2)
Prepare a list of five activities that you perform daily in which natural resources can be conserved or energy utilisation can be minimised.
3)
Is water conservation necessary? Give reasons.
4)
Suggest a few useful ways of utilising waste water.
5)
What is the importance of forest as a resource?

CBSE 10th Standard Science Subject Our Environment Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Give two differences between food chain and food web.
2)
Name the wastes which are generated in your house daily. What measures would you take for their disposal?
3)
Suggest suitable mechanism (s) for waste management in fertilizer industries.
4)
What are the by-products of fertiliser industries? How do they affect the environment?
5)
Explain some harmful effects of agricultural practices on the environment.

CBSE 10th Standard Science Subject Sources of Energy Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Which is the process used to harness nuclear energy these days? Explain it briefly.
2)
a) How can solar energy be harnessed?
b) Mention any two limitations in using solar energy.
c) How are these limitations overcome?
3)
a) Make a list of conventional and non-conventional sources of energy.
b) Give a brief description of harnessing one non-conventional source of energy.
4)
a) Why is there a need for harnessing non-conventional sources of energy?
b) How can energy be harnessed from the sea in different ways?
5)
What are the environmental consequences of using fossil fuels? Suggest the steps to minimize the pollution caused by various source of energy including non-conventional sources of energy?

CBSE 10th Standard Science Subject Magnetic Effects of Electric Current Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
(a) Why does a magnetic compass needle pointing North and South in the absence of a nearby magnet get deflected when a bar magnet or a current carrying loop is brought near it.
(b) Describe some salient features of magnetic lines of field.
2)
With the help of a labelled circuit diagram illustrate the pattern of field lines of the magnetic field around a current carrying straight long conducting wire. How is the right hand thumb rule useful to find direction of magnetic field associated with a current carrying conductor?
3)
Explain with the help of a labelled diagram the distribution of magnetic field due to a current through a circular loop. Why is it that if a current carrying coil has 'n' turns the field produced at any point is n times as large as that produced by a single turn?
4)
Describe the activity that shows that a current-carrying conductor experiences a force perpendicular to its length and the external magnetic field. How does Fleming's left-hand rule help us to find the direction of the force acting on the current carrying conductor?
5)
Explain the phenomenon of electromagnetic induction. Describe an experiment to show that a current is set up in a closed loop when an external magnetic field passing through the loop increases or decreases.

CBSE 10th Standard Science Subject Electricity Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
State Ohm's law? How can it be verified experimentally? Does it hold good under all conditions? Comment
2)
How will you infer with the help of an experiment that the same current flows through every part of the circuit containing three resistances in series connected to a battery?
3)
How will you conclude that the same potential difference exist across three resistors connected in a parallel arrangement to a battery?
4)
Find out the following in the electric circuit given in figure
(a) Effective resistance of two 8\(\Omega\) resistors in the combination
(b) Current flowing through 4\(\Omega\) resistor.
(c) Potential difference across 4\(\Omega\) resistance
(d) Power dissipated in 4\(\Omega\) resistor.
(e) Difference in ammeter readings, if any.
5)
Find out the following in the electric circuit given in Figure
(a) Effective resistance of two 8 \(\Omega\) resistors in the combination
(b)Current flowing through 4 \(\Omega\) resistor
(c) Potential difference across 8 \(\Omega\) resistance
(d) Power dissipated in 4 \(\Omega\) resistor
(e) Difference in ammeter readings, if any.

CBSE 10th Standard Science Subject How do Organisms Reproduce Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Write two points of difference between asexual and sexual types of reproduction.Describe why variations are observed in the offspring formed by sexual reproduction.
2)
Distinguish between a gamete and zygote.Explain their roles in sexual reproduction.
3)
What are various ways to avoid pregnancy?Elaborate any one method.
4)
How does fertilisation take place? Fertilisation occurs once in a month.Comment.
5)
What is the placenta? Mention its role during pregnancy?

CBSE 10th Standard Science Subject Control and Coordination Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
What constitutes the central and peripheral nervous systems? How are the components of central nervous system protected?
2)
Mention one function for each of these hormones:
(a) Thyroxin
(b) Insulin
(c) Adrenaline
(d) Growth hormone
(e) Testosterone
3)
Name various plant hormones. Also give their physiological effects on plant growth and development.
4)
What are reflex action? Give two examples. Explain a reflex arc.
5)
"Nervous and hormonal system together perform the function of control and coordination in human beings." Justify the statement.

CBSE 10th Standard Science Subject Life Processes Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Describe the alimentary canal of man.
2)
Explain the process of breathing in man.
3)
Explain the important of soil for plant growth.
4)
How do carbohydrates, proteins and fats get digested in human beings?
5)
Explain the mechanism of photosymthesis.

CBSE 10th Standard Science Subject Acids, Bases and Salts Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
In the following schematic diagram for the preparation of hydrogen gas as shown in Figure, what would happen if following changes are made?

(a) In place of zinc granules, same amount of zinc dust is taken in the test tube.
(b) Instead of dilute sulphuric acid, dilute hydrochloric acid is taken.
(c) In place of zinc, copper turnings are taken.
(d) Sodium hydroxide is taken in place of dilute sulphuric acid and the tube is heated.
2)
For making cake, baking powder is taken. If at home your mother uses baking soda instead of baking powder in cake,

(a) How will it affect the taste of the cake and why?

(b) How can baking soda be converted into baking powder?

(c) What is the role of tartaric acid added to baking soda?
3)
A metal carbonate X on reacting with an acid gives a gas which when passed through a solution Y gives the carbonate back. On the other hand, a gas G that is obtained at anode during electrolysis of brine is passed on dry Y; it gives a compound Z, used for disinfecting drinking water. Identity X, Y, G and Z.
4)
A dry pellet of a common base B, when kept in open absorbs moisture and turns sticky. The compound is also a by-product of chlor-alkali process. Identify B. What type of reaction occurs when B is treated with an acidic oxide? Write a balanced chemical equation for one such solution.
5)
A sulphate salt of Group 2 element of the Periodic Table is a white, soft substance. Which can be moulded into different shapes by making its dough. When this compound is left in open for sometime, it becomes a solid mass and cannot be used for moulding purposes. Identify the sulphate salt and why does it show such a behaviour? Give the reaction involved.

CBSE 10th Standard Science Subject Periodic Classification of Elements Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
An element is placed in 2nd Group and 3rd Period of the Periodic Table, burns in presence of oxygen to form a basic oxide.
(a) Identify the element.
(b) Write the electronic configuration.
(c) Write the balanced equation when it burns in the presence of air.
(d) Write a balanced equation when this oxide is dissolved in water.
(e) Draw the electron dot structure for the formation of this oxide.
2)
An element A (atomic number 17) reacts with an element B (atomic number 20) to form a divalent halide.
(a) Where in the periodic table are elements A and B placed?
(b) Classify A and B as metal (s), non-metal(s) or metalloid(s).
(c) What will be the nature of oxide of element B? Identify the nature of bonding in the compound formed.
(d) Draw the electron dot structure of the divalent halide.
3)
Atomic number of a few elements are given below 10, 20, 7, 14
(a) Identify the elements.
(b) Identify the Group number of these elements in the Periodic Table.
(c) Identify the Periods of these elements in the Periodic Table.
(d) What would be the electronic configuration for each of these elements?
(e) Determine the valency of these elements.
4)
Mendeleev' predicted the existence of certain elements not known at that time and named two of them as Eka-silicon and Eka-aluminium.
(a) Name the elements which have taken the place of these elements.
(b) Mention the group and the period of these elements in the Modern Periodic Table.
(c) Classify these elements as metals, non-metals or metalloid.
(d) How many valence electrons are present in each one of them?
5)
(a) Electropositive nature of the element(s) increases down the group and decreases across the period
(b) Electronegativity of the element decreases down the group and increases across the period
(c) Atomic size increases down the group and decreases across a period (left to right)
(d) Metallic character increases down the group and decreases across a period.
On the basis of the above trends of the Periodic Table, answer the following about the elements with atomic numbers 3 to 9.
(a) Name the most electropositive element among them.
(b) name the most electronegative element.
(c) Name the element with smallest atomic size.
(d) Name the element which shows maximum valency.

CBSE 10th Standard Science Subject Light Reflection and Refraction Ncert Exemplar 5 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
(i) " A convex lens can form a magnified erect as well as magnified inverted image of an object placed in front of it. " Draw ray diagram to justify this statement stating the position of the object with respect to the lens in each case.
(ii) As object of height 4 cm is placed at a distance of 20 cm from a concave lens of focal length 10 cm. Use lens formula to determine the position of the image formed.
2)
(a) State the laws of refraction of light. Explain the term absolute refractive index of a medium and write an expression to relate it with the speed of light in vaccum.
(b) The absolute refractive indices of two media 'A' and 'B' are 2.0 and 1.5 respectively. If the speed of light in medium 'B' is \({ 2\times 10 }^{ 8 }\) m/s. calculate the speed of light in : (i) Vacuum, (ii) medium 'A'
3)
(a) Draw ray diagram to show the refraction of light through a glass slab and mark angle of refraction and the lateral shift suffered by the ray of the light while passing through the slab.
(b) If the refractive index of glass for light going from air to glass is 3/2, find the refractive index of air for light going from glass to air.
4)
List the sign conventions for reflection of light by spherical mirrors. Draw a diagram and apply these conventions in the determination of focal length of a spherical mirror which forms a three times magnified real image of an object placed 16 cm in front of it.
5)
To construct a ray diagram we use two light rays which are so chosen that it is easy to know their directions after reflection from mirror. List these two rays and state the path of these rays after reflection. Use these rays to locate the image of an object placed between centre of curvature and focus of a concave mirror.

CBSE 10th Standard Science Subject Light Reflection and Refraction Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Write laws of refraction. Explain the same with the help of ray diagram, when a ray of light passes through a rectangular glass slab.
2)
Size of image of an object by a mirror having a focal length of 20 cm is observed to be reduced to 1/3 rd of its size. At what distance the object has been placed from the mirror? What is the nature of the image and the mirror?
3)
The image of a candle flame formed by a lens is obtained on a screen placed on the other side of the lens. If the image is three times the size of the flame and the distance between lens and image is 80 cm, at what distance should the candle be placed from the lens? What is the nature of the image at a distance of 80 cm and the lens?
4)
Define power of a lens. What is its unit? One student uses a lens of focal length 50 cm and another of - 50 cm. What is the nature of the lens and its power used by each of them?
5)
(a) Define focal length of a divergent lens.
(b) A divergent lens of focal length 30 cm forms the image of an object of size 6 cm on the same side as the object at a distance of 15 cm from its optical centre. Use lens formula to determine the distance of the object from the lens and the size of the image formed.
(c) Draw a ray diagram to show the formation of image in the above situation.

CBSE 10th Standard Science Subject Heredity and Evolution Ncert Exemplar 5 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Study the following cross and showing self-pollination in F1, fill in the blank answer the question that follows
\(\underset { Round,yellow }{ RRYY } \times \underset { Wrinkled,green }{ rryy } F1-\underset { Round,yellow }{ Rr\quad Yy\times } \)
2)
(a) In question 8, what are the combinations of character in the F₂ progeny?
(b) What are their ratios?
3)
Give the basic features of the mechanism of inheritance.
4)
Give reasons for the appearance of new combinations of characters in the F₂ progeny.
5)
Define evolution. How does it occur? Describe how fossils provide us evidences in support of evolution.

CBSE 10th Standard Science Subject Heredity and Evolution Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Does geographical isolation of individuals of a species lead to formation of a new species? Provide a suitable explanation.
2)
Bacteria have a simpler body plan when compared with human beings. Does it mean that human beings are more evolved than bacteria? Provide a suitable explanation.
3)
All the human races like Africans, Asians, Europeans, Americans and others might have evolved from a common ancestor. Provide a few evidences in support of this view.
4)
Differentiate between inherited and acquired characters. Give one example for each type.
5)
Give reasons why acquired characters are not inherited.

CBSE 10th Standard Science Subject Periodic Classification of Elements Ncert Exemplar 5 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Atomic number of a few elements are given below 10, 20, 7, 14
(a) Identify the elements.
(b) Identify the Group number of these elements in the Periodic Table.
(c) Identify the Periods of these elements in the Periodic Table.
(d) What would be the electronic configuration for each of these elements?
(e) Determine the valency of these elements.
2)
Mendeleev' predicted the existence of certain elements not known at that time and named two of them as Eka-silicon and Eka-aluminium.
(a) Name the elements which have taken the place of these elements.
(b) Mention the group and the period of these elements in the Modern Periodic Table.
(c) Classify these elements as metals, non-metals or metalloid.
(d) How many valence electrons are present in each one of them?
3)
(a) Electropositive nature of the element(s) increases down the group and decreases across the period
(b) Electronegativity of the element decreases down the group and increases across the period
(c) Atomic size increases down the group and decreases across a period (left to right)
(d) Metallic character increases down the group and decreases across a period.
On the basis of the above trends of the Periodic Table, answer the following about the elements with atomic numbers 3 to 9.
(a) Name the most electropositive element among them.
(b) name the most electronegative element.
(c) Name the element with smallest atomic size.
(d) Name the element which shows maximum valency.
4)
An element A which is a yellow solid at room temperature shows catenation and allotropy. A forms two oxides which are also formed during the thermal decomposition of ferrous sulphate crystals and are the major air pollutants.
(a) Identify the element A
(b) Write the electronic configuration of A
(c) Write the balanced chemical equation for the thermal decomposition of ferrous sulphate crystals?
(d) What would be the nature (acidic/ basic ) of oxides formed?
(e) Locate the Position of the element in the Modern Periodic Table.
5)
An element X of group 15 exists as diatomic molecule and combines with hydrogen at 773 K in presence of the catalyst to form a compound, ammonia which has a characteristic pungent smell.
(a) Identify the element X. How many valence electrons does it have?
(b) Draw the electron dot structure of the diatomic molecule of X. What type of bond is formed in it?
(c) Draw the electron dot structure for ammonia and what type of bond is formed in it?

CBSE 10th Standard Science Subject Periodic Classification of Elements Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Which element has :
(a) two shells, both of which are completely filled with electrons?
(b) the electronic configuration 2, 8, 2?
(c) a total of three shells, with four electron in its valence shell?
(d) a total of two shells, with three electrons in its valence shell?
(e) twice as many electrons in its second shell as in its first shell?
2)
(a) What property do all elements in the same column of the Periodic Table as boron have in common?
(b) What property do all elements in the same column of the Periodic Table as fluorine have in common?
3)
The position of three elements A, B and C in the Periodic Table are shown below:

Group 16 Group 17

- -

- A

- -

B C

(a) State whether A is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller in size than B?
(d) Which type of ion, cation or anion, will be formed by element A?
4)
In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21 and 38. Which of these have physical and chemical properties resembling calcium?
5)
Compare and contrast the arrangement of elements in Mendeleev's Periodic Table and the Modern Periodic Table.

CBSE 10th Standard Science Subject Carbon and Its Compounds Ncert Exemplar 5 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
A compound C (molecular formula, C₂H₄O₂) reacts with Na - metal to form a compound R and evolves a gas which burns with a pop sound. Compound C on treatment with an alcohol A in presence of an acid forms a sweet smelling compound S (molecular formula, C₃H₆O₂). On addition of NaOH to C, it also gives R and water. S on treatment with NaOH solution gives back R and A. Identify C, R, A, s and write down the reactions involved.
2)
How would you bring about the following conversions? Name the process and write the reaction involved.
a) Ethanol to ethene.
b) Propanol to propanoic acid
3)
Draw the possible isomers of the compound ith molecular formula C₃H₆O and also give their electron dot structures.
4)
An organic compound A on heating with concentrated H₂SO₄ forms a compound B which on addition of one mole of hydrogen in presence of Ni forms a compound C. One mole of compound C on combustion forms two moles of CO₂ and 3 moles of H₂O. Identify the compounds A, B and C and write the chemical equations of the reactions involved.
5)
Look at the below figure and answer the following questions:

a) What change would you observe in the calcium hydroxide solution taken in tube B?
b) Write the reaction involved in test tubes A and B respectively.
c) If ethanol is given instead of ethanoic acid, would you expect the same change?
d) How can a solution of lime water be prepared in the laboratory?

CBSE 10th Standard Science Subject Carbon and Its Compounds Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
A salt X is formed and a gas is evolved when ethanoic acid reacts with sodium hydrogen carbonate. Name the salt X and the gas evolved. Describe an activity and draw the diagram of the apparatus to prove that the evolved gas is the one which you have named. Also, write chemical equation of the reaction involved.
2)
a) What are hydrocarbons? Give examples
b) Give the structural differences between saturated and unsaturated hydrocarbons with two example each.
c) What is a functional group? Give example of four different functional groups.
3)
Name the reaction which is commonly used in the conversion of vegetable oils to fats. Explain the reaction involved in detail.
4)
a) Write the formula and draw electron dot structure of carbon tetrachloride?
b) What is saponification? Write the reaction involved in this process.
5)
Esters are sweet-smelling substances and are used in making perfumes. Suggest some activity and the reaction involved for the preparation of an ester with well labeled diagram.

CBSE 10th Standard Science Subject Metals and Non-Metals Ncert Exemplar 5 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
(i) Why Sulphuric acid is called the 'king of chemicals'?
(ii) Name the gas evolved when :
(a) Concentrated Sulphuric acid acts on Sulphur.
(b) Dilute Sulphuric acid acts on Sodium carbonate.
(iii) State the colour change you would observe on adding concentrated sulphuric acid to :
(a) Blue Copper sulphate crystals.
(b) Colourless cane-sugar crystals.
2)
(a) Write chemical equations for the reactions involved in obtaining pure alumina from the mineral bauxite which has impurities of iron oxide and silica.
(b) Draw a labelled diagram of the electrolytic tank cell used for the extraction of aluminium from alumina.
3)
(a) What is corrosion of metals? Name one metal which does not corrode and one which corrodes on being kept in atmosphere.
(b) How will you show that the rusting of iron needs oxygen and moisture at the same time?
4)
(a) What is an 'activity series' of metals? Arrange the metals Zn, Mg, Al, Cu and Fe in a decreasing order of reactivity.
(b) What would you observe when you put
(i) Some zinc pieces into blue copper sulphate solution?
(ii) Some copper pieces into green ferrous sulphate solution?
(c) Name a metal which combines with hydrogen gas. Name the compound formed.
5)
(a) Name one main ore of Aluminium. Write its formula. Which two main impurities are associated with this ore?
(b) Describe with chemical equations, the method employed for the enrichment of the above named ore.

CBSE 10th Standard Science Subject Metals and Non-Metals Ncert Exemplar 5 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
A non-metal A which is the largest costituent of air, when heated with H₂ in 1 : 3 ratio in the presence of catalyst (Fe) gives a gas B. On heating with O₂ it gives an oxide C. If this oxide is passed into water in the presence of air it gives an acid D which acts as a strong oxidising agent.
(a) Identify A, B, C and D
(b) To which group of periodic table does this non - metal belong?
2)
Explain the following
(a) Reactivity of Al decreases if it is dipped in HNO₃.
(b) Carbon cannot reduce the oxides of Na or Mg
(c) NaCl is not a conductor of electricity in solid state whereas it does conduct electricity in aqueous solution as well as in molten state.
(d) Iron articles are galvanised
(e) Metals like Na, K, Ca and Mg are never found in their free state in nature.
3)
Of the three metals X, Y and Z, X reacts with cold water, Y with hot water and Z with steam only. Identify X, Y and Z and also arrange them in order of increasing reactivity.
4)
An element A burns with golden flame in air. It reacts with another element B, atomic number 17 to give a product C. An aqueous solution of product C on electrolysis gives a compound D and liberates hydrogen. Identify A, B, C and D. Also write down the equations for the reactions involved.
5)
Give the steps involved in the extraction of metals of low and medium reactivity from their respective sulphide ores.

CBSE 10th Standard Science Subject Metals and Non-Metals Ncert Exemplar 3 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Why do ionic compounds conduct electricity?
2)
Why do covalent compounds have low melting point?
3)
What are 'mineral' and 'ore'?
4)
State five points of differences between ionic compound and covalent compound.
5)
Point out any 3 differences between calcination and roasting.

CBSE 10th Standard Science Subject Metals and Non-Metals Ncert Exemplar 3 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Describe with a labelled diagram, the froth Floatation Process used to separate the gangue from a Sulphide ore.
2)
On adding dilute HCl acid to copper oxide powder, the solution formed is blue-green. Predict the new compound formed which imparts a blue-green colour to the solution.
3)
Name a major ore from which iron is extracted. Write chemical equations for the reactions that take place in the blast furnace for the extraction of iron from this ore.
4)
(a) Name the chief ore of iron. Write its formula.
(b) How is an iron ore concentrated? Describe it briefly.
(c) Draw a labelled diagram of the blast furnace used in the extraction of iron from its concentrated ore.
5)
From amongst the metals sodium, calcium, aluminium, copper and magnesium, name the metal.
(i) which reacts with water only on boiling and
(ii) another which does not react even with steam.

CBSE 10th Standard Science Subject Sustainable Management of Natural Resources Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Prepare a list of five items you use daily in the school. Identify from the list such items that can be recycled.
2)
List two advantages associated with water harvesting at the community level.
3)
What measures would you take to conserve electricity in your house?
4)
Although coal and petroleum are produced by degradation of bio-mass, yet we need to conserve them. Why?
5)
Suggest a few measures for controlling carbon dioxide levels in the atmosphere.

CBSE 10th Standard Science Subject Our Environment Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Why is improper disposal of waste a curse to environment?
2)
Write the common food chain of a pond ecosystem.
3)
What are the advantages of cloth bags over plastic bags during shopping?
4)
Why are crop fields known as artificial ecosystems?
5)
Explain the role of decomposers in the environment?

CBSE 10th Standard Science Subject Sources of Energy Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 26, 2021 - View & Read

1)
Write two different ways of harnessing energy from ocean.
2)
What steps would you suggest to minimize environment pollution caused by burning of fossil fuels?
3)
What is the role of a plane mirror and a glass sheet in a solar cooker?
4)
Mention three advantages of a solar cell.
5)
What is biomass? What can be done to obtain bio-energy using biomass?

CBSE 10th Standard Science Subject Magnetic Effects of Electric Current Ncert Exemplar 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
(a) Name four appliances where an electric motor, a rotating device that converts electrical energy into mechanical energy, is used as an important component.
(b) In what respect motors are different from generators?
2)
What is the role of the two conducting stationary brushes in a simple electric motor?
3)
(a) What is the different between a direct current and an alternating current?
(b) How many times does AC used in India change direction in one second?
4)
(a) What is the role of fuse, used in series with any electrical appliance?
(b) Why should a fuse with defined rating not be replaced by one with a larger rating?
5)
A magnetic compass needle is placed in the plane of paper near point A as shown in Figure. In which plane should a straight current carrying conductor be placed so that it passes through A and there is no change in the deflection of the compass? Under what condition is the deflection maximum and why?

CBSE 10th Standard Science Subject Magnetic Effects of Electric Current Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
List three methods of producing magnetic field.
2)
Name some devices in which electric motors are used .
3)
Two circular coils A and B are placed close to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.
4)
When does an electric short circuit occur?
5)
What is the function of an earth wire ? Why is its necessary to earth metallic appliances?

CBSE 10th Standard Science Subject Electricity Ncert Exemplar 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Why is parallel arrangement used in domestic wiring?
2)
A child has drawn the electric circuit to study Ohm's law as shown in Figure. His teacher told that the circuit diagram needs correction. Study the circuit diagram and redraw it after making all the corrections.
3)
Three 2 \(\Omega\) resistors, A, B and C, are connected as shown in Figure. Each of them dissipates energy and can withstand a maximum power of 18 W without melting Find the maximum current that can flow through the three resistors?
4)
Draw a circuit diagram of an electric circuit containing a cell, a key, an ammeter, a resistor of 2 \(\Omega\) in series with a combination of two resistors (4 \(\Omega\) each) in parallel and a voltmeter across the parallel combination. Will the potential difference across the 2 \(\Omega\) resistors to be the same as that across the parallel combination of 4 \(\Omega\) resistor? Give reason
5)
B₁, B₂ and B₃ three identical bulbs connected as shown in Figure when the entire three bulbs glow, a current of 3A is recorded by the ammeter A.

(i) What happens to the glow of the other two bulbs when the bulb B₁ gets fused?
(ii) What happens to the reading of A₁, A₂, A₃ and A when the bulb B₂ gets fused?
(iii) How much power is dissipated in the circuit when all the three bulbs glow together?

CBSE 10th Standard Science Subject Electricity Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Should the resistance of an ammeter below or high? Give reason.
2)
How does use of a fuse wire protect electric appliances?
3)
What is electrical resistivity? In a series electrical circuit comprising a resistor made up of a metallic wire, the ammeter reads 5 A. The reading of the ammeter decreases to half when the length of the wire is doubled. Why?
4)
What is the commerical unit of electrical energy? Represent it in terms of joules.
5)
(a) A current of 1 ampere flows in a series circuit containing an electric lamp and a conductor of 5\(\Omega \) when connected to a 10 V battery. Calculate the resistance of the electric lamp.
(b) Now if a resistance of 10\(\Omega \) is connected in parallel with this series combination, what change in current flowing through 5\(\Omega \) conductors and potential difference across the lamp will take place? Give reason.

CBSE 10th Standard Science Subject Human Eye and the Colourful World Ncert Exemplar 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
A student sitting at the back of the classroom cannot read clearly the letters written on the blackboard.What advice will a doctor give to her?Draw ray diagram for the correction of this defect.
2)
How are we able to see nearby and also the distant object clearly?
3)
How will you use two identical prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as white light?Draw the diagram.
4)
Draw a ray diagram showing through a prism when a narrow beam of white light is incident on one of its refracting surfaces.Also indicate the order of the colours of the spectrum obtained.
5)
Is the position of a star as seen by us its true position? Justify your answer.

CBSE 10th Standard Science Subject Human Eye and the Colourful World Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Draw ray diagram each showing (i)myopic eye and (ii) hypermetropic eye.
2)
A student sitting at the back of the classroom cannot read clearly the letters written on the blackboard.What advice will a doctor give to her?Draw ray diagram for the correction of this defect.
3)
How are we able to see nearby and also the distant object clearly?
4)
A person needs a lens of power -4.5D for correction of her vision
(a)What kind of defect in vision is she suffering from?
(b)What is the focal length of the corrective lens?
(c)What is the nature of the corrective lens?
5)
How will you use two identical prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as white light?Draw the diagram.

CBSE 10th Standard Science Subject Light Reflection and Refraction Ncert Exemplar 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
A ray of light falls normally on the surface of a transparent glass slab. Draw a ray diagram to show its path and also mark angle of incidence and angle of emergence.
2)
List four characteristics of the images formed by plane mirrors.
3)
State two positions in which a concave mirror produces a magnified image of a give object. List two different between the two images.
4)
List four specific characteristics of the images of the objects formed by convex mirrors.
5)
The image of a candle flame placed at a distance of 30 cm from a spherical lens is formed on a screen placed on the other side of the lens at a distance of 60 cm from the optical centre of the lens. Identify the type of lens and calculate its focal length. If the height of the flame is 3 cm, find the height of its imaged.

CBSE 10th Standard Science Subject Light Reflection and Refraction Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Why does a light ray incident on a rectangular glass slab immersed in any medium emerges parallel to itself? Explain using a diagram.
2)
How is the refractive index of a medium related to the speed of light? Obtain an expression for refractive index of a medium with respect to another in terms of speed of light in these two media?
3)
Refractive index of diamond with respect to glass is 1.6 and absolute refractive index of glass is 1.5. Find out the absolute refractive index of diamond.
4)
A convex lens of focal length 20 cm can produce a magnified virtual as well as real image. Is this a correct statement? If yes, where shall the object is placed in each case for obtaining these images?
5)
Shoba finds out that sharp image of the window pane of her science laboratory is formed at a distance of 15 cm from the lens. She now tries to focus the building visible to her outside the window instead of the window pane without disturbing the lens. In which direction will she move the screen to obtain a sharp image of the building? What is the approximate focal length of this lens?

CBSE 10th Standard Science Subject Heredity and Evolution Ncert Exemplar 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Explain the role of artificial selection in organic evolution.
2)
What is the main difference between sperms and eggs of humans? Write the importance of this difference.
3)
How are variant genotypes produced?
4)
What are homologous organs? Can the wings of a butterfly and the wings of a bat be regarded as homologous?Why?
5)
Give an example of a body characteristics used to determine how close two species are in terms of evolution and explain it.

CBSE 10th Standard Science Subject Heredity and Evolution Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
How is the sex of a newborn determined in humans?
2)
Do genetic combination of mothers play a significant role in determining the sex of a new born?
3)
Mention three important features of fossils which help in the study of evolution.
4)
Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics?
5)
In evolutionary terms, can we say which among bacteria, spiders, fish and chimpanzees have a better body design? Why or why not?

CBSE 10th Standard Science Subject How do Organisms Reproduce Ncert Exemplar 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Where is the zygote located in the flower after fertilization?
2)
Reproduction is linked to stability of population of a species.Justify the statement.
3)
How are general growth and sexual maturation different from each other?
4)
Trace the path of sperm during ejaculation and mention the gland and their functions associated with the male reproductive system
5)
What changes are observed in the uterus if fertilisation does not occur?

CBSE 10th Standard Science Subject How do Organisms Reproduce Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
In a bisexual flower inspite of the young stamens being removed artificially, the flower produces fruit.Provide a suitable explanation for the above situation.
2)
Can you consider cell division as a type of reproduction in unicellular? Give one reason
3)
What is a clone? Why do offsprings formed by asexual reproduction exhibit remarkable similarity?
4)
Explain how, offspring and parents of organisms reproducing sexually have the same number of chromosomes?
5)
Colonies of yeast fail to multiply in water, but multiple in sugar solution.Give one reason for this.

CBSE 10th Standard Science Subject Control and Coordination Ncert Exemplar 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Name the plant hormones responsibility for the following:
(a) Elongation of cells
(b) Growth of stem
(c) Promotion of cell division
(d) Falling of senescent leaves.
2)
What happens at the synapse between two neurons?
3)
Answer the following:
(a) Which hormone is responsible for the changes noticed in females at puberty?
(b) Dwarfism results due to deficiency of which hormone?
(c) Blood sugar level rises due to deficiency of which hormone?
(d) Iodine is necessary for the synthesis of which hormone?
4)
In the given figures, (a), (b) and (c), which appears more accurate and why?
5)
Label the parts of a neuron in the given figure.

CBSE 10th Standard Science Subject Control and Coordination Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Name the plant hormones responsibility for the following:
(a) Elongation of cells
(b) Growth of stem
(c) Promotion of cell division
(d) Falling of senescent leaves.
2)
Answer the following:
(a) Which hormone is responsible for the changes noticed in females at puberty?
(b) Dwarfism results due to deficiency of which hormone?
(c) Blood sugar level rises due to deficiency of which hormone?
(d) Iodine is necessary for the synthesis of which hormone?
3)
Answer the following:
(a) Name the endocrine gland associated with brain?
(b) Which gland secretes digestive enzymes as well as hormones?
(c) Name the endocrine gland associated with kidneys?
(d) Which endocrine gland is present in males but not in females?
4)
Label the parts (a), (b), (c) and (d) and show the direction of flow of electrical signals in the following figure.
5)
Label the endocrine glands in the given figure.

CBSE 10th Standard Science Subject Life Processes Ncert Exemplar 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Why is the rate of breathing in aquatic organism much faster than in terrestrial organisms?
2)
Why is blood circulation in human heart called double circulation?
3)
What is the advantage of having four chambered heart?
4)
Mention the major event during photosynthesis.
5)
Name the energy currency in the living organisms.When and where is it produced?

CBSE 10th Standard Science Subject Life Processes Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
"All plants give out oxygen during day and carbon dioxide during night".Do you agree with this statement? Give reason
2)
How do the guard cells regulate opening and closing of stomatal pores?
3)
Two green plants are kept separately in oxygen free containers, one in the dark and the other in continuous light.Which one will live longer? Give reasons.
4)
If a plant is releasing carbon dioxide and taking in oxygen during the day, does it mean that there is no photosynthesis occurring? Justify your answer.
5)
Why do fishes die when taken out of water?

CBSE 10th Standard Science Subject Periodic Classification of Elements Ncert Exemplar 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
How does the electronic configuration of an atom relate to its position in the Modern Periodic Table?
2)
Arrange the following elements in increasing order of their atomic radii.
(a) Li, Be, F, N
(b) Cl, At, Br I
3)
Identify and name the metals out of the following elements whose electronic configurations are given below
(a) 2,8,2
(b) 2,8,1
(c) 2,8,7
(d) 2,1
4)
Write the formula of the product formed when the element X (atomic number 19) combines with the element Y (atomic number 17). Draw its electronic dot structure. What is the nature of the bond formed?
5)
Arrange the following elements in the increasing order of their metallic character Mg, Ca, K, Ge, Ga

CBSE 10th Standard Science Subject Periodic Classification of Elements Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
The three elements A,B and C with similar properties have atomic masses X, Y and Z respectively. The mass of Y is approximately equal to the average mass of X and Z. What is such an arrangement of elements called as? Give one example of such a set of elements.
2)
Elements have been arranged in the following sequence on the basis of their increasing atomic masses.
F,Na,Mg,Al,Si,P,S,Cl,Ar,K
(a) Pick two sets of elements which have similar properties.
(b) The given sequence represents which law of classification of elements?
3)
Can the following groups of elements be classified as Dobereiner's triad?
(a) Na, Si, Cl
(b) Be, Mg, Ca
Atomic mass of Be 9; Na 23; Mg 24; Si 28; Cl 35; Ca 40
Explain by giving reason.
4)
In Mendeleev's Periodic Table the elements were arranged in the increasing order of their atomic masses. However, cobalt with atomic mass of 58.93 amu was placed before nickel having an atomic mass of 58.71 amu. Give reason for the same.
5)
" Hydrogen occupies a unique position in Modern Periodic Table". Justify the statement.

CBSE 10th Standard Science Subject Carbon and Its Compounds Ncert Exemplar 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Write the structural formulae of all the isomers of hexane.
2)
Write the names of the following compounds
3)
Identify and name the functional groups present in the following compounds.
4)
What is the role of metal or reagents written on arrows in the given chemical reactions?
5)
Write the name of the following compounds:

CBSE 10th Standard Science Subject Carbon and Its Compounds Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Draw the electron dot structure of ethyne and also draw its structural formula.
2)
A compound X is formed by the reaction of a carboxylic acid C₂H₄O₂ and an alcohol in presence of a few drops of H₂SO₄. The alcohol on oxidation with alkaline kMnO₄ followed by acidification gives the same carboxylic acid as used in this reaction. Give the names and structures of (a) carboxylic acid, (b) alcohol and (c) the compound X. Also write the reaction.
3)
Why detergents are better cleansing agents than soaps? Explain.
4)
Name the functional groups present in the following compounds.
(a) CH₃COCH₂CH₂CH₃
(b) CH₃CH₂CH₂COOH
(c) CH₃CH₂CH₂CH₂CHO
(d) CH₃CH₂OH
5)
How is ethene prepared from ethanol? Give the reaction involved in it.

CBSE 10th Standard Science Subject Metals and Non-Metals Ncert Exemplar 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
An alkali metal A gives a compound B (molecular mass = 40) on reacting with water. The compound B gives a soluble compound C on treatment with aluminium oxide. Identify A, B and C and give the reaction involved.
2)
Give the reaction involved during extraction of zinc from its ore by
(a) Roasting of zinc ore
(b) Calcination of zinc ore
3)
A metal M does not liberate hydrogen from acids but reacts with oxygen to give a black colour product and also explain the reaction of M with oxygen.
4)
An element forms an oxide A₂O₃ which is acidic in nature. Identify A as a metal are non-metal.
5)
A solution of CuSO₄ was kept in an iron pot. After few days the iron pot was found to have a number of holes in it. Explain the reason in terms of reactivity. Write the equation of the reaction involved.

CBSE 10th Standard Science Subject Metals and Non-Metals Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Iqbal treated a lustrous element M with sodium hydroxide. He observed the formation of bubbles in reaction mixture. He made the same observations when this element was treated with hydrochloric acid. Suggest how he will identify the produced gas. Write chemical equations for both the reactions.
2)
During extraction of metals, electrolytic refining is used to obtain pure metals.
(a) Which material will be used as anode and cathode for refining of silver metal by this process?
(b) Suggest a suitable electrolyte also.
(c) In this electrolytic cell, where do we get pure silver after passing electric current?
3)
Why should the metal sulphides and carbonates be converted to metal oxides in the process of extraction of metal from them?
4)
Generally, when metals are treated with mineral acids, hydrogen gas is liberated but when metals (except Mn and Mg), treated with HNO₃ , hydrogen is not liberated, why?
5)
Compound X and aluminium are used to join railway tracks.
(a) Identify the compound X
(b) Name the reaction
(c) Write down its reaction.

CBSE 10th Standard Science Subject Acids, Bases and Salts Ncert Exemplar 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Name the acid present in ant sting and give its chemical formula. Also give the common method to get relief from the discomfort caused by the ant sting.
2)
What happens when nitric acid is added to egg shell?
3)
A student prepared solutions of (i) and acid and (ii) a base in two separate beakers. She forgot to label the solutions and litmus paper is not available in the laboratory. Since both the solutions are colourless, how will she distinguish between the two?
4)
How would you distinguish between baking powder and washing soda by heating?
5)
Give the uses of bleaching powder.

CBSE 10th Standard Science Subject Acids, Bases and Salts Ncert Exemplar 2 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Write word equations and then balanced equations for the reaction taking place when
(a) dilute sulphuric acid reacts with zinc granules.
(b) dilute hydrochloric acid reacts with magnesium ribbon
(c) dilute sulphuric acid reacts with aluminium powder
(d) dilute hydrochloric acid reacts with iron filings.
2)
Why do acids not show acidic behaviour in the absence of water?
3)
Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic aicd \((CH_3COOH)\) is added to test tube B. Amount and concentration taken for both the acids are same. In which test tube, will the fizzing occur more vigorously and why?
4)
Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain.
5)
What is a neutralisation reaction? Give two examples.

CBSE 10th Standard Science Subject Light Reflection and Refraction Ncert Exemplar 1 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
What is meant by power of a lens?
2)
A ray of light is incident on a concave mirror along its principal axis. What will be the angle of reflection?
3)
What will happen to ray of light when it travels from rarer medium to a denser medium?
4)
What does negative sign in the value of magnification of a mirror indicate?
5)
Between which two points of a concave mirror should an object be placed to obtain a magnification of - 3?

CBSE 10th Standard Science Subject Light Reflection and Refraction Ncert Exemplar 1 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
The outer surface of a hollow sphere of aluminium of radius 50 cm is to be used as a mirror. What will be the focal length of this mirror? Which type of spherical mirror will it provide?
2)
Define one dioptre.
3)
The size of an object is 2 cm. The magnification produced by a mirror is +1. What is the size of the image?
4)
When a ray of light passes from a denser medium to a rarer medium which angle is greater? Angle of incidence or angle of refraction
5)
" The refractive index of carbon disulphide is 1.63." What is the meaning of this statement in relation to speed of light?

CBSE 10th Standard Science Subject Heredity and Evolution Ncert Exemplar 1 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
A normal pea plant bearing coloured flowers suddenly start producing white flowers. What could be the possible cause?
2)
Mention any two recessive traits of garden pea.
3)
Mention the characteristics on the basis of which duck - biled platypus is considered as a link between reptiles and mammals.
4)
Is it true that when a new species is emerged, the old species will be eliminated? Why?
5)
What will be the percentage of 'ab' gametes produced by AaBb parent?

CBSE 10th Standard Science Subject Heredity and Evolution Ncert Exemplar 1 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Wild cabbage was converted into number of variants like cauliflower, broccoli and cabbage by man. What is this process known as?
2)
What is speciation?
3)
What will be the sex of a baby if sperm carrying X chromosome fertilizes egg in human beings? Why?
4)
A woman with blonde curly hair married a man with black soft hair. All of their children in first generation had black soft hair but in next generation children had different combinations in the ratio of 9 : 3 : 3 : 1. State the law that governs this expression.
5)
What happened when Mendel crossed two traits of a character in a pea plant?

CBSE 10th Standard Science Subject Metals and Non-Metals Ncert Exemplar 1 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Name the catalyst used in the manufacture of ammonia by Haber's Process.
2)
What makes silver turn black and copper turn green when kept exposed for few days?
3)
Name two allotropes of carbon.
4)
Name three common types of ores where metal exists in nature.
5)
Name two metals both of which are very ductile as well as very malleable.

CBSE 10th Standard Science Subject Metals and Non-Metals Ncert Exemplar 1 Mark Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
A non-metal X exists in two different forms Y and Z, Y is the hardest natural substance, whereas Z is a good conductor of electricity. Identify X, Y and Z.
2)
What is the purpose of quenching steel?
3)
State a reaction in which SO₂ acts as an oxidising agent.
4)
Name a non-metal which is in liquid state and a metal which is found in liquid state.
5)
Name two metals which do not react with oxygen.

CBSE 10th Standard Science Subject Sustainable Management of Natural Resources Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Ground water will not be depleted due to
2)
Opposition to the construction of large dams is due to
3)
Khadins, Bundhis, Ahars and Kattas are ancient structures that are examples for
4)
Pick the combination of terms which has no fossil fuel.
5)
Select the eco-friendly activity among the following

CBSE 10th Standard Science Subject Sustainable Management of Natural Resources Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
From the list given below pick the item that is not a natural resource
2)
The most rapidly dwindling natural resource in the world is
3)
The most appropriate definition of a natural resource is that it is a substance/ commodity that is
4)
The main cause for abundant coliform bacteria in the river Ganga is
5)
The pH of water sample collected from a river was found to be acidic in the range of 3.5 - 4.5, on the banks of the river were several factories that were discharging effluents into the river. The effluents of which one of the following factories is the most likely cause for lowering the pH of river water?

CBSE 10th Standard Science Subject Our Environment Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
The percentage of solar radiation absorbed by all the green plants for the process of photosynthesis is about
2)
What will happen if deer is missing in the food chain given below?
Grass\(\rightarrow\)Deer\(\rightarrow\)Tiger
3)
The decomposers in an ecosystem
4)
If a grass hopper is eaten by a frog, then the energy transfer will be from
5)
Disposable plastic plates should not be used because

CBSE 10th Standard Science Subject Our Environment Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Which one of the following is an artificial ecosystem?
2)
In a food chain, the third trophic level is always occupied by
3)
An ecosystem includes
4)
In the given food chain, suppose the amount of energy at fourth trophic level is 5 kJ, what will be the energy available at the producer level?
Grass\(\longrightarrow\)Grasshopper\(\longrightarrow\)Frog\(\longrightarrow\)Snake\(\longrightarrow\)Hawk
5)
Accumulation of non-biodegradable pesticides in the food chain in increasing amount at each higher trophic level is known as

CBSE 10th Standard Science Subject Sources of Energy Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
The power generate in a wind mill
2)
Choose the correct statement?
3)
In a hydroelectric power plant more electrical power can be generated if water falls from a greater height because
4)
Choose the incorrect statement regarding wind power.
5)
Choose the incorrect statement

CBSE 10th Standard Science Subject Sources of Energy Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Which of the following is a non-renewable source of energy
2)
Acid rain happen because
3)
Fuel used in thermal power plant is
4)
In a hydro power plant
5)
Which is the ultimate source of energy?

CBSE 10th Standard Science Subject Human Eye and the Colourful World Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to
2)
The human eye forms the image of an object at its
3)
The change in focal length of eye lens is caused by action of
4)
A person cannot see distinctly object kept beyond 2m.This defect can be corrected by using a lens of power
5)
A prism ABC is placed in different orientations. A narrow beam of white light is incident on the prism as shown in Figure. In which of the following cases, after dispersion, the third colour from the top corresponds to the colour of the sky?

CBSE 10th Standard Science Subject Heredity and Evolution Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
The two versions of a trait (character) which are brought in by the male and female gametes are situated on
2)
In peas, a pure tall plant (TT) is crossed with a short plant (tt). The ratio of pure tall plants to short plants in F₂ is
3)
The number of pair (s) of sex chromosomes in the zygote of humans is
4)
The theory of evolution of species by natural selection was given by
5)
Some dinosaurs had feathers although they could not fly but birds have feathers that help them to fly. In the context of evolution this means that

CBSE 10th Standard Science Subject Heredity and Evolution Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Exchange of genetic material takes place in
2)
Two pink coloured flowers on crossing resulted in 1 red, 2 pink and 1 white flower progeny. The nature of the cross will be
3)
A cross between a tall plant (TT) and short pea plant (tt) resulted in progeny that were all tall plants because
4)
Which of the following statement is incorrect?
5)
If a round, green seeded pea plant (RR yy) is crossed with wrinkled, yellow seeded pea plant, (rr YY) the seeds produced in FI generation are

CBSE 10th Standard Science Subject How do Organisms Reproduce Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
InRhizopus, tubular thread-like structures bearing sporangia at their tips are called
2)
Vegetative propagation refers to formation of new plants from
3)
Length of pollen tube depends on the distance between
4)
Offspring formed as a result of sexual reproduction exhibit more variations because
5)
Reproduction is essential for living organisms in order to

CBSE 10th Standard Science Subject How do Organisms Reproduce Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
In a flower, the parts that produce male and female gametes (germ cells) are
2)
Characters transmitted from parents to offspring are present in
3)
Characters that are transmitted from parents to offspring during reproduction show
4)
A feature of reproduction that is common Amoeba, Spirogyra and Yeast is that
5)
In Spirogyra, asexual reproduction takes place by

CBSE 10th Standard Science Subject Control and Coordination Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Which of the following is not an involuntary action?
2)
When a person is suffering from severe cold, he or she cannot
3)
Which statement is not true about thyroxin?
4)
Dwarfism result due to
5)
Dramatic changes of body features associated with puberty are mainly because of secretion of

CBSE 10th Standard Science Subject Control and Coordination Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Which of the following statement is correct about receptors?
2)
Electrical impulse travels in a neuron from
3)
In a synapse, chemical signal is transmitted from
4)
In a neuron, conversion of electrical signal to a chemical signal occurs at/in
5)
Which is the correct sequence of the components of a reflex arc?

CBSE 10th Standard Science Subject Life Processes Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
The opening and closing of the stomatal pore depends upon
2)
Which of the first enzyme to mix with food in the digestive tract?
3)
Lack of oxygen in muscles often leads to cramps among cricketers. This results due to
4)
Choose the correct path of urine in our body
5)
During deficiency of oxygen in tissues of human beings, pyruvic acid i converted into lactic acid in the

CBSE 10th Standard Science Subject Life Processes Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Which of the following statement(s) is (are) true about respiration?
(i)During inhalation, ribs inward and diaphragm is raised
(ii)In the alveoli, exchange of gases takes place i.e., oxygen from alveolar air diffuse into blood and carbon dioxide from blood into alveolar air
(iii)Haemoglobin has greater affinity for carbon dioxide than oxygen
(iv)Alveoli increase surface area for exchange of gases
2)
Which is the correct sequence of air passage during inhalation?
3)
During respiration exchange of gases take place in
4)
Which of the following statement (s) is are true about heart?
(i)Left atrium receives oxygenated blood from different parts of body while right atrium receives deoxygenated blood from lungs
(ii)Left ventricle pumps oxygenated blood to different body parts while right ventricle pumps deoxygenated blood to lungs
(iii)Left atrium transfer oxygenated blood to right ventricle which sends it to different body parts
(iv)Right atrium receives deoxygenated blood from different parts of the body while left ventricle pumps oxygenated blood to different parts of the body
5)
What prevents backflow of blood inside the heart during contraction?

CBSE 10th Standard Science Subject Periodic Classification of Elements Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Arrange the following elements in the order of their increasing nonmetallic character : Li, O, C, Be, F
2)
What type of oxide would Eka-aluminium form?
3)
On moving from left to right in a period in the periodic table, the size of the atom.
4)
Which of the following set of elements is written in order of their increasing metallic character?
5)
Which one of the following depicts the correct representation of atomic radius(r) of an atom?

CBSE 10th Standard Science Subject Periodic Classification of Elements Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Which of the following statements is not a correct statement about the trends when going from left to right across the periods of periodic Table?
2)
Element X forms a chloride with the formula XCl₂ , which is a solid a high melting point. X would most likely be in the same group of the Periodic Table as :
3)
Upto which element, the Law of Octaves was found to be applicable
4)
According to Mendeleev's Periodic Law, the elements were arranged in the periodic table in the order of
5)
Arrange the following elements in the order of their increasing nonmetallic character : Li, O, C, Be, F

CBSE 10th Standard Science Subject Carbon and Its Compounds Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Structural formula of benzene is
2)
The correct structural formula of butanoic acid is
3)
The correct electron dot structure of a water molecule is
4)
Which of the following is not a straight chain hydrocarbon?
5)
Which among the following are unsaturated hydrocarbons?
(i)

(ii)

(iii)

(iv)

CBSE 10th Standard Science Subject Carbon and Its Compounds Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Carbon exists in the atmosphere in the form of
2)
A molecule of ammonia (NH₃) has
3)
Buckminsterfullerene is an allotropic form of
4)
\(CH_3- {CH_2 }-OH \xrightarrow [ ]{ Alkaline \ KMnO_4+Heat } CH_3- COOH\)
In the above given reaction, alkaline KMnO₄ acts as
5)
Oils on treating with hydrogen in the presence of palladium or nickel catalyst form fats. This is an example of

CBSE 10th Standard Science Subject Metals and Non-Metals Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Although metals form basic oxides, which of the following metals form an amphoteric oxide?
2)
Generally, non-metals are not conductors of electricity. Which of the following is a good conductor of electricity?
3)
Electrical wires have a coating of an insulating material. The material, generally used is
4)
Which of the following non-metals is a liquid?
5)
Which of the following can undergo a chemical reaction?

CBSE 10th Standard Science Subject Metals and Non-Metals Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Which of the following properly is generally not shown by metals?
2)
The ability of metals to be drawn into thin wire is known as
3)
Aluminium is used for making cooking utensils. Which of the following properties of aluminium are responsible for the same?

(i) Good thermal conductivity

(ii) Good electrical conductivity

(iii) Ductility

(iv) High melting point
4)
Which one of the following metals do not react with cold as well as hot water?
5)
Which of the following oxide(s) of iron would be obtained on prolonged reaction of iron with steam?

CBSE 10th Standard Science Subject Acids, Bases and Salts Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Equal volumes of hydrochloric acid and sodium hydroxide solutions of same concentration are mixed and the pH of the resulting solution is checked with a pH paper. What would be the colour obtained?
2)
Which of the following is (are) true when HCl (g) is passed through water?

(i) It does not ionise in the solution as it is a covalent compound.

(ii) It ionises in the solution

(iii) It gives both hydrogen and hydroxyl ion in the solution

(iv) It forms hydronium ion in the solution due to the combination of hydrogen ion with water molecule
3)
Which of the following statement is true for acids?
4)
Which of the following are present in a dilute aqueous solution of hydrochloric acid?
5)
Identify the correct representation of reaction occurring during chloralkali process

CBSE 10th Standard Science Subject Acids, Bases and Salts Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
A solution turns red litmus blue; its pH is likely to be?
2)
A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains.
3)
10 ml of a solution of NaOH is found to be completely neutralised by 8 ml of a given solution of HCl. If we take 20 ml of the same solution of NaOH, the amount of HCl solution required to neutralise it will be
4)
Which one of the following types of medicines is used for treating indigestion?
5)
What happens when a solution of an acid is mixed with a solution of a base in a test tube?

(a) The temperature of the solution increases

(b) The temperature of the solution decreases

(c) The temperatures of the solution remains the same

(d) Salt formation takes place

CBSE 10th Standard Science Subject Chemical Reactions and Equations Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Which of the following gases can be used for storage of fresh sample of an oil for a long time?
2)
The following reaction is used for the preparation of oxygen gas in the laboratory
2KClO₃(s) \(\frac{Heat}{Catalyst}\) 2KCl + 3O₂(g)
Which of the following statement(s) is (are) correct about the reaction?
3)
Which one of the following processes involves chemical reactions?
4)
In which of the following chemical equations, the abbreviations represent the correct states of the reactants and products involved temperature?
5)
Which of the following are combination reactions?
(i) 2KClO₃ \(\overset { \Delta }{ \rightarrow } \) 2KCl + 3O₂
(ii) MgO + H₂O \(\rightarrow\) Mg(OH)₂
(iii) 4Al + 3O₂ \(\rightarrow\) 2Al₂O₃
(iv) Zn + FeSO₄ \(\rightarrow\) ZnSO₄ + Fe

CBSE 10th Standard Science Subject Chemical Reactions and Equations Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Fe₂O₃ + 2Al \(\rightarrow\) Al₂O₃ + 2Fe.
The above reaction is an example of a
2)
The following reaction: 4NH₃(g) + 5O₂(g) \(\rightarrow\) 4NO(g) + 6H₂O(g) is an example of a
(i) displacement reaction
(ii) combination reaction
(iii) redox reaction
(iv) neutralisation reaction
3)
Which of the following statements about the given reaction are correct?
3Fe(s) + 4H₂O(g) \(\rightarrow\) Fe₃O₄(s) + 4H₂(g)
(i) Iron metal is getting oxidised
(ii) Water is getting reduced
(iii) Water is acting as reducing agent
(iv) Water is acting as oxidising agent
4)
Which of the following are exothermic processes?
(i) Reaction of water with quicklime
(ii) Dilution of an acid
(iii) Evaporation of water
(iv) Sublimation of camphor(crystals)
5)
A dilute ferrous sulphate solution was gradually added to the beaker containing acidified permanganate solution. The light purple colour of the solution fades and finally disappears. Which of the following is the correct explanation for the observation?

CBSE 10th Standard Science Subject Magnetic Effects of Electric Current Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Which of the following correctly describes the magnetic field near a long straight wire ?
2)
The phenomenon of electromagnetic induction is
3)
The device used for producing electric current is called a
4)
The essential difference between an AC generator and a DC generator is that
5)
At the time of short circuit, the current in the circuit

CBSE 10th Standard Science Subject Magnetic Effects of Electric Current Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
The strength of magnetic field inside a long current carrying straight solenoid is
2)
To convert an AC generator into DC generator
3)
The most important safety method used for protecting home appliances from short circuiting or overloading is
4)
If the key in the arrangement (below figure) is taken out (the circuit is made open) and magnetic field lines are drawn over the horizontal plane ABCD, the lines are
5)
A constant current flows in a horizontal wire in the plane of the paper from east to west as shown in the figure. The direction of the magnetic field at a point will be North to South

CBSE 10th Standard Science Subject Electricity Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
A cell, a resistor, a key and ammeter are arranged as shown in the circuit diagrams. The current recorded in the ammeter will be
2)
In the following circuits, heat produced in the resistor or combination of resistors connected to a 12 V battery will be
3)
Identify the circuit in which the electrical components have been properly connected.
4)
The proper representation of series combination of cells obtaining maximum potential is
5)
A student carries out an experiment and plots the V-I graph of three samples of nichrome wire with resistances R₁, R₂ and R₃ respectively. Which of the following is true?

CBSE 10th Standard Science Subject Electricity Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
In an electrical circuit three incandescent bulbs A, B and C of rating 40 W, 60 W and 100 W respectively are connected in parallel to an electric source. Which of the following is likely to happen regarding their brightness?
2)
In an electrical circuit two resistors of 2\(\Omega \) and 4\(\Omega \) respectively are connected in series to a 6 V battery. The heat dissipated by the 4\(\Omega \) resistor in 5s will be
3)
An electric kettle consumes 1 Kw of electric power when operated at 220 V. A fuse wire of what rating must be used for it?
4)
Two resistors of resistance 2\(\Omega \) and 4\(\Omega \) when connected to a battery will have
5)
Unit of electric power may also be expressed as

CBSE 10th Standard Science Subject Light Reflection and Refraction Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm infront of the mirror. The focal length of this mirror is.
2)
Which of the following statements is true?
3)
Rays from Sun converge at a point 15 cm in front of a concave mirror. Where an object should be placed so that size of its image is equal to the size of the object?
4)
In torches search lights and headlights of vehicles the bulb is placed
5)
You are given water, mustard oil, glycerine and kerosene. In which of these media a ray light incident obliquely at same angle would bend the most?

CBSE 10th Standard Science Subject Light Reflection and Refraction Ncert Exemplar MCQ Questions 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Which of the following can make a parallel beam of light when light from a point source is incident on it?
2)
Under which of the following conditions a concave mirror can form an image larger than the actual object?
3)
Magnification produced by a rear view mirror fitted in vehicles
4)
The path of a ray of light coming from air passing through a rectangular glass slab traced by four students are shown as A, B, C and D in Figure. Which one of them is correct?
5)
Which of the following ray diagram is correct for the ray of light incident on a lens shown in Figure?

CBSE 10th Standard Science Subject Ncert Exemplar MCQ Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Which one of the following types of medicines is used for treating indigestion?
2)
Which of the following phenomena occur, when a small amount of acid is added to water?

(i) Ionisation (ii) Neutralisation (iii) Dilution (iv) Salt formation
3)
Metals are refined by using different methods. Which of the following metals are refined by electrolytic refining?
(i) Au (ii) Cu (iii) Na (iv) K
4)
Which one of the following figures correctly describes the process of electrolytic refining?
5)
Pentane has the molecular formula C₅H₁₂ . It has

CBSE 10th Standard Science Subject Ncert Exemplar MCQ Questions 2021 Part - II - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
A solution turns red litmus blue; its pH is likely to be?
2)
An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change?
3)
To protect tooth decay we are advised to brush our tech regularly. The nature of the tooth paste commonly used is
4)
Which of the following are present in a dilute aqueous solution of hydrochloric acid?
5)
Stainless steel is very useful material for our life. In stainless steel, iron is mixed with

CBSE 10th Standard Science Subject Ncert Exemplar MCQ Questions 2021 Part - I - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
A solution reacts with crushed egg-shells to give a gas that turns lime-water milky. The solution contains.
2)
An aqueous solution turns red litmus solution blue. Excess addition of which of the following solution would reverse the change?
3)
If a few drops of a concentrated acid accidentally spills over the hand of a student, what should be done?
4)
Equal volumes of hydrochloric acid and sodium hydroxide solutions of same concentration are mixed and the pH of the resulting solution is checked with a pH paper. What would be the colour obtained?
5)
Which of the following are not ionic compounds ?
(i) KCl (ii) HCl (iii) CCl₄ (iv) NaCl

CBSE 10th Standard Science Subject Ncert Exemplar 3 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9 respectively. Which solution is
(i) neutral
(ii) strongly alkaline
(iii) strongly acidic
(iv) weakly acidic
(v) weakly alkaline
Arrange the pH in increasing order of H⁺ion concentration.
2)
Describe with a labelled diagram, the froth Floatation Process used to separate the gangue from a Sulphide ore.
3)
Give reasons for the following :
(i) Metals are regarded as electro-positive elements
(ii) When a piece of copper metal is added to a solution of zinc sulphate, no change takes place, but the blue colour of copper sulphate fades away when a piece of zinc is placed in its solution.
(iii) Articles made of alimunium do not corrode even though aluminium is an active metal.
4)
Give reasons for the following:
(a) Metals can be given different shapes according to our needs.
(B) Hydrogen is not evolved when a metal reacts with nitric acid.
5)
What are 'mineral' and 'ore'?

CBSE 10th Standard Science Subject Ncert Exemplar 3 Mark Questions 2021 Part - I - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9 respectively. Which solution is
(i) neutral
(ii) strongly alkaline
(iii) strongly acidic
(iv) weakly acidic
(v) weakly alkaline
Arrange the pH in increasing order of H⁺ion concentration.
2)
Describe with a labelled diagram, the froth Floatation Process used to separate the gangue from a Sulphide ore.
3)
Give reasons for the following :
(i) Metals are regarded as electro-positive elements
(ii) When a piece of copper metal is added to a solution of zinc sulphate, no change takes place, but the blue colour of copper sulphate fades away when a piece of zinc is placed in its solution.
(iii) Articles made of alimunium do not corrode even though aluminium is an active metal.
4)
Give reasons for the following:
(a) Metals can be given different shapes according to our needs.
(B) Hydrogen is not evolved when a metal reacts with nitric acid.
5)
What are 'mineral' and 'ore'?

CBSE 10th Standard Science Subject Ncert Exemplar 1 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Is burning of a candle, a physical change or a chemical change?
2)
Name two metals which do not react with oxygen.
3)
What are two types of reducing agents used to reduce metal oxide?
4)
Name two metals with very low melting point.
5)
What will be the blood groups of offspring's produced by the parents having following genotype?

CBSE 10th Standard Science Subject Ncert Exemplar 1 Mark Questions 2021 Part - II - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
Write a balanced chemical equation for the following reaction. Ethanol is warmed with ethanoic acid to form ethyl acetate in the presence of concentrated HSO₄,₂SO₄.
2)
Name two metals which do not react with oxygen.
3)
Name two allotropes of carbon.
4)
What is speciation?
5)
If the sperm bearing Y - Chromosome fertilizes an egg, the child born will not be entirely like his father? Why?

CBSE 10th Standard Science Subject Ncert Exemplar 1 Mark Questions 2021 Part - I - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
What is the purpose of quenching steel?
2)
What are ionic bonds?
3)
Name two allotropes of carbon.
4)
Name a reducing agent that may be used to obtain manganese from manganese dioxide.
5)
What will be the blood groups of offspring's produced by the parents having following genotype?

CBSE 10th Standard Science Subject Ncert Exemplar 2 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
A student prepared solutions of (i) and acid and (ii) a base in two separate beakers. She forgot to label the solutions and litmus paper is not available in the laboratory. Since both the solutions are colourless, how will she distinguish between the two?
2)
The following reaction takes place when aluminium powder is heated with MNO₂
\({ 3MnO }_{ 2 }+4Al(s)\rightarrow 3Mn(l)+{ 2Al }_{ 2 }{ O }_{ 3 }+Heat\)
(a) Is aluminium getting reduced?
(b) Is MnO₂ getting oxidised?
3)
In electron dot structure, the valence shell electrons are represented by crosses or dots.
a) The atomic number of chlorine is 17. Write its electronic configuration
b) Draw the electron dot structure of chlorine molecule
4)
Identify and name the functional groups present in the following compounds.
5)
Write the formulae of chloride of Eka-silicon and Eka-aluminium, the elements predicted by Mendeleev.

CBSE 10th Standard Science Subject Ncert Exemplar 2 Mark Questions 2021 Part - II - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
A milkman adds a very small amount of baking soda to fresh milk.
(i) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
(ii) Why does this milk take a long time to set as curd?
2)
During extraction of metals, electrolytic refining is used to obtain pure metals.
(a) Which material will be used as anode and cathode for refining of silver metal by this process?
(b) Suggest a suitable electrolyte also.
(c) In this electrolytic cell, where do we get pure silver after passing electric current?
3)
A non-metal A is an important constituent of our food and forms two oxides B and C. Oxide B is toxic whereas C causes global warming
(a) Identify A, B and C
(b) To which Group of Periodic Table does a belong?
4)
A solution of CuSO₄ was kept in an iron pot. After few days the iron pot was found to have a number of holes in it. Explain the reason in terms of reactivity. Write the equation of the reaction involved.
5)
Catenation is the ability of an atom to form bonds with other atoms of the same element. it is exhibited by both carbon and silicon. Compare the ability of catenation of the two elements. Give reasons.

CBSE 10th Standard Science Subject Ncert Exemplar 2 Mark Questions 2021 Part - I - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
In a test-tube, hydrochloric acid is poured over a few zinc granules. List two observations that suggest that a chemical reaction has occurred.
2HCl+Zn\(\rightarrow \) ZnCl₂+H₂
2)
Why do acids not show acidic behaviour in the absence of water?
3)
What happens when nitric acid is added to egg shell?
4)
During extraction of metals, electrolytic refining is used to obtain pure metals.
(a) Which material will be used as anode and cathode for refining of silver metal by this process?
(b) Suggest a suitable electrolyte also.
(c) In this electrolytic cell, where do we get pure silver after passing electric current?
5)
Name the constituents of solder alloy. Which property of solder makes it suitable for welding electrical wires?

CBSE 10th Standard Science Subject Ncert Exemplar 5 Mark Questions With Solution 2021 - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
A dry pellet of a common base B, when kept in open absorbs moisture and turns sticky. The compound is also a by-product of chlor-alkali process. Identify B. What type of reaction occurs when B is treated with an acidic oxide? Write a balanced chemical equation for one such solution.
2)
a) Write the formula and draw electron dot structure of carbon tetrachloride?
b) What is saponification? Write the reaction involved in this process.
3)
Which group of elements could be placed in Mendeleev's Periodic Table without disturbing the original order? Give reason
4)
Explain the process of breathing in man.
5)
All the human races like Africans, Asians, Europeans, Americans and others might have evolved from a common ancestor. Provide a few evidences in support of this view.

CBSE 10th Standard Science Subject Ncert Exemplar 5 Mark Questions 2021 Part - II - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
A sulphate salt of Group 2 element of the Periodic Table is a white, soft substance. Which can be moulded into different shapes by making its dough. When this compound is left in open for sometime, it becomes a solid mass and cannot be used for moulding purposes. Identify the sulphate salt and why does it show such a behaviour? Give the reaction involved.
2)
What is an alloy? How is an alloy made? List two purpose of making alloys. Mention the constituents and two properties of each of the following alloys.
(i) Stainless steel
(ii) Brass
3)
(a) Name one main ore of Aluminium. Write its formula. Which two main impurities are associated with this ore?
(b) Describe with chemical equations, the method employed for the enrichment of the above named ore.
4)
Esters are sweet-smelling substances and are used in making perfumes. Suggest some activity and the reaction involved for the preparation of an ester with well labeled diagram.
5)
Compare and contrast the arrangement of elements in Mendeleev's Periodic Table and the Modern Periodic Table.

CBSE 10th Standard Science Subject Ncert Exemplar 5 Mark Questions 2021 Part - I - by Prerna - Bangalore - May 25, 2021 - View & Read

1)
For making cake, baking powder is taken. If at home your mother uses baking soda instead of baking powder in cake,

(a) How will it affect the taste of the cake and why?

(b) How can baking soda be converted into baking powder?

(c) What is the role of tartaric acid added to baking soda?
2)
A non-metal A which is the largest costituent of air, when heated with H₂ in 1 : 3 ratio in the presence of catalyst (Fe) gives a gas B. On heating with O₂ it gives an oxide C. If this oxide is passed into water in the presence of air it gives an acid D which acts as a strong oxidising agent.
(a) Identify A, B, C and D
(b) To which group of periodic table does this non - metal belong?
3)
(i) Why Sulphuric acid is called the 'king of chemicals'?
(ii) Name the gas evolved when :
(a) Concentrated Sulphuric acid acts on Sulphur.
(b) Dilute Sulphuric acid acts on Sodium carbonate.
(iii) State the colour change you would observe on adding concentrated sulphuric acid to :
(a) Blue Copper sulphate crystals.
(b) Colourless cane-sugar crystals.
4)
a) What are hydrocarbons? Give examples
b) Give the structural differences between saturated and unsaturated hydrocarbons with two example each.
c) What is a functional group? Give example of four different functional groups.
5)
Look at the below figure and answer the following questions:

a) What change would you observe in the calcium hydroxide solution taken in tube B?
b) Write the reaction involved in test tubes A and B respectively.
c) If ethanol is given instead of ethanoic acid, would you expect the same change?
d) How can a solution of lime water be prepared in the laboratory?

CBSE 10th Standard Science Subject Our Environment Chapter Case Study Questions With Solution 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

Advancement of the technology has resulted in improvement of our lifestyle and has also changed our attitude. When the human population was low and technology was in its infancy, the various kinds of solid wastes generated due to human activities were easily degraded by decomposers present in nature and it did not create any Significant harmful effect on the environment. In the recent times, however human population has increased tremendously and the technology has become greatly advanced. These two factors have contributed Significantly in the deterioration of our environment due to addition of number of wastes.
(i) Samaira took three different types of solid wastes P,Q, R and buried them under the soil in a pot, as she wanted to study their rate of decomposition. Her findings are shown in the given graph

Select the option that correctly identifies P, Q and R

P	Q	R
(a) Polythene bag	Leather bag	Fruit peel
(b) Used syringes	Broken glass	Leather purse
(c) Cardboard	Cow dung	Rubber mat
(d) Human excreta	Paper cup	Cow dung

(ii) Which of the following statements regarding solid wastes is correct?
(a) Change in the packaging technology has resulted in generation of lot of solid wastes.
(b) Dumping of solid wastes could reduce the fertility of the soil leading to reduction in crop yield.
(c) Accumulation of solid waste could cause increased incidents of disease in a locality.
(d) All of these
(iii) Teacher kept few solid wastes in her class as given

Jute bag (I), Tube light (II), Aluminium (oil (III), Paper cup (IV), Fruits (V), Glass tumbler (VI), Hedge trimming (VII), Plastic bag (VIII), Metal keys (IX), DDT (X)

She asked students to arrange them in group A (Biodegradable) and group B (Non-biodegradable). Select the student that has grouped the items correctly.

(a) Tarun -	Group A: I, IV, V,VII,	Group B : II, III, VI, VIII, IX, X
(b) Shivani -	Group A : I, III, V,VII, X	Group B : II, IV, VI, VIII, IX
(c) Neha -	Group A: II, III, IV, V, IX	Group A: II, III, IV, V, IX
(d) Advait -	Group A : I, III, IV, V,X	Group B : II, VI, VII, VIII, IX

(iv) Select the option that incorrectly matches the type of solid waste and its correct disposal system
(a) Plastic bottle - Send for recycling
(b) Used tea leaves and kitchen waste - Collect in a pit to form compost
(c) Used syringes and needle - Wash and reused
(d) Municipal solid waste and fecal sludge - Buried in low lying areas to level uneven surface of land
(v) Given graph shows time taken by different types of materials to decompose.

Which of the following substances could be anon-biodegradable material?

(a) X

(b) Y

(c) Z

(d) None of these

2)
In any given ecosystem, all living organisms are linked in a systematic chain with respect to their mode of manufacturing food/feeding habits. This sequential interlinking of organisms involving transfer of food energy from producers through a series of organisms with repeated eating and being eaten is called the food chain. A food chain may have 3-4 trophic levels.
(i) Which of the following statements regarding food chain is incorrect?
(a) It is a single straight pathway through which food energy travels in the ecosystem.
(b) It adds adaptability and competitiveness to the organisms.
(c) Presence of isolated food chains adds to instability of the ecosystem.
(d) Food chain binds up inorganic nutrients of the ecosystem.
(ii) Consider the following food chain.
Grass \(\longrightarrow\)A \(\longrightarrow\)Frog \(\longrightarrow\) Snake\(\longrightarrow\)Eagle
Which of the following can be placed at A?

(a) Grasshopper (b) Rabbit (c) Phytoplankton (d) Rat

(iii) Select the correct food chain.
(a) Aquatic plants \(\longrightarrow\) Tadpole \(\longrightarrow\)Water beetle\(\longrightarrow\)Pike\(\longrightarrow\)Perch
(b) Grass\(\longrightarrow\)Grasshopper\(\longrightarrow\)Snake\(\longrightarrow\) Frog\(\longrightarrow\) Eagle
(c) Grass\(\longrightarrow\) Rabbit\(\longrightarrow\) Wild cat\(\longrightarrow\) Tiger
(d) Zooplankton \(\longrightarrow\) Phytoplankton \(\longrightarrow\)Small fish\(\longrightarrow\)Fish
(iv) Food chains are sustained by producers and _____________.

(a) herbivores (b) carnivores (c) omnivores (d) decomposers

(v) Select the incorrect statement.
(a) Food chain may terminate at level of herbivore
(b) Food chain is always straight
(c) Food chain may have 3-5 trophic levels
(d) In a food chain, 80 to 90% of potential energy is lost as heat, at each transfer
3)
Alternatives are always available in nature which results in a sort of interlocking pattern or food web. For instance, if a particular species of producers get destroyed by a disease in an ecosystem, herbivores of that area can feed on other species. Also in a food web, any given species may operate simultaneously at more than one trophic level
(i) Refer to the given food web.

What will be the effect on the food web if population of water fleas get eliminated?
(a) Population of water beetles will increase.
(b) Population of insect larvae will remain unaffected.
(c) Population of small fish will decrease.
(d) Population of frog will increase.
(ii) In the given food web, which organism operates at both primary and tertiary consumer level?

(a) Small fish (b) Frog (c) Water fleas (d) Tadpole

(iii) Refer to the given food web.

Which of the following statemethe given food web is correct?
(a) When population of U decreases, population of R ants regarding nd V will increase.
(b) When population of Q decreases, population of R, T and U will increase.
(c) When population of R increases, population of S will increase.
(d) When population of S increases, population of R, T and U will also increase.
(iv) Which of the following statements is correct?
(a) Food webs provide alternative pathways of food availability.
(b) Greater alternatives available in a food web make the ecosystem more stable.
(c) Food webs also help in ecosystem development.
(d) All of these
(v) Food webs make a natural ecosystem ____________ than an man-made ecosystem

(a) unstable (b) stable (c) variable (d) inconsistent

4)

Some harmful non-biodegradable chemicals, i.e., pesticides (e.g., DDT) and heavy metals (e.g., mercury, arsenic cadmium, etc.) enter the bodies of organism through the food chain and go on concentrating at each trophic level. This phenomenon is called bio-magnification or biological magnification.
(i) Refer to the given food chain
Phytoplankton \(\longrightarrow\) Zooplankton \(\longrightarrow\)Small fish \(\longrightarrow\) Large fish\(\longrightarrow\)Fish eating birds
If concentration of DDT in small fish is estimated to be 0.5 ppm, then amount of DDT in zooplankton and large fish would respectively be

(a) 0.04 ppm, 2ppm

(b) 2 ppm, 0.04 ppm

(c) 0.04 ppm, 0.04 ppm

(d) 2 ppm, 0.5 ppm.

(ii) Refer to the given table.

Organism	Amount of cadmium
A	0.5 ppm
B	25ppm
C	0.003 ppb
D	2ppm
E	0.04ppm

According to the given data. The correct order in a food chain will be

(a) E\(\rightarrow\)C\(\rightarrow\)D\(\rightarrow\)A\(\rightarrow\)B	(b) B\(\rightarrow\)D\(\rightarrow\)A\(\rightarrow\)E\(\rightarrow\)C
(c) C\(\rightarrow\)E\(\rightarrow\)A\(\rightarrow\)D\(\rightarrow\)B	(d) C\(\rightarrow\)E\(\rightarrow\)A\(\rightarrow\)B\(\rightarrow\)D

(iii) A group of scientists analysed samples of five different animals from a river for possible accumulation of DDT in their body due to bio-magnification. The result obtained is shown in the given graph.
The correct order of the food chain operating in a river is

(a) S\(\rightarrow\)P\(\rightarrow\)Q\(\rightarrow\)R	(b) S\(\rightarrow\)Q\(\rightarrow\)R\(\rightarrow\)P
(c) P\(\rightarrow\)R\(\rightarrow\)Q\(\rightarrow\)S	(d) P\(\rightarrow\)Q\(\rightarrow\)S\(\rightarrow\)R

(iv) Higher amount of DDT disturb calcium metabolism of birds. This results in

(a) thickening of their egg shells	(b) premature breaking of eggs
(c) death of their embryos	(d) both (b) and (c)

(v) When animals are sprayed with poisons, they may die immediately, but their bodies still contain the poison. The poison in their bodies will then be passed on to the animals which eat them. What would be the consequence of a mass poisoning of the rabbit population in a grazing food chain and why?
(a) Plants would die quickly as they are eaten by rabbits
(b) Grasshopper would die quickly as all the animals in the food web would be affected
(c) Western rattlesnakes would quickly become poisoned as they eat rabbits
(d) Hawk would become poisoned as they feed on rabbits

5)

Ozone layer is present in the earth's atmosphere. It is in the form of a protective shield. It contains three oxygen atoms (O₃) which are formed as a consequence of photochemical reactions in the environment. Ozone absorbs harmful ultraviolet radiations of the sun. In this way, it protects all living beings on the earth. The thinning of ozone layer due to various human activities allows more UV radiations to pass through it which leads to harmful effects on man, animals and plants.
(i) Ozone layer is present in which layer of the atmosphere?

(a) Troposphere

(b) Mesosphere

(c) Stratosphere

(d) Thermosphere

(ii) Enhanced UV-radiations would affect humans and other animals causing
(a) skin cancer
(b) blindness and increased chances of cataract in eyes
(c) malfunctioning of the immune system
(d) all of these
(iii) Read the given statements regarding ozone.
I. Ozone hole was first discovered over Montreal in 1976.
II. Ozone is a result of photochemical reactions in which starting molecule is oxygen.
III. Harmful chemicals produce active chlorine in presence of UV radiations, that destroys ozone layers.
IV. Ozone absorbs UV-radiations in the range of 800 - 1100 A.
Select the option that correctly identifies them as true (T) and false (F).

I	II	III	IV
(a) F	T	T	F
(a) F	F	T	T
(c) T	T	F	F
(d) T	F	T	T

(iv) Which of the following are related to depletion of ozone layer?

(a) Chlorofluorocarbons	(b) Halons
(c) Carbon tetrachloride	(d) All of these

(v) Refer to the given events regarding thinning of ozone layer and arrange them in a sequence.
I. Active chlorine is produced in presence of UV radiations.
II. CFCs are released in the air.
III. Ozone layer in the stratosphere become thin.
IV. CFCs enter from troposphere into stratosphere.
V. Use of CFCs in refrigerators and air conditioners as coolants.
VI. Active chlorine destroy ozone by converting it into oxygen.

(a) V \(\rightarrow\) II \(\rightarrow\) I \(\rightarrow\) VI\(\rightarrow\)IV \(\rightarrow\) III	(b) V \(\rightarrow\) II \(\rightarrow\) IV \(\rightarrow\)I \(\rightarrow\)VI \(\rightarrow\) III
(c) V\(\rightarrow\) I \(\rightarrow\) II \(\rightarrow\) III\(\rightarrow\)VI \(\rightarrow\) IV	(d) V \(\rightarrow\) IV\(\rightarrow\) II \(\rightarrow\)I \(\rightarrow\) III \(\rightarrow\) VI

CBSE 10th Standard Science Subject Our Environment Chapter Case Study Questions 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

Various steps of a food chain can be represented sequence wise with producers at base, herbivores above them, followed by primary carnivores and finally the top carnivore at the top. This graphic representation of ecological parameters like number, biomass, energy at different trophic levels is called ecological pyramid. Different types of pyramids are pyramid of energy, pyramid of biomass and pyramid of number.
(i) Refer to the given figure where various trophic levels are represented as P, Q, Rand S. At which level is maximum and minimum energy available respectively?

(a) P, S

(b) S, P

(c) P, R

(d) Q, S

(ii) On the basis of your knowledge, select the pyramid of biomass operating in a grassland ecosystem

(iii) Which of the following food chains is most likely represented by the given pyramid of number?

(a) Tree \(\rightarrow\) Aphid \(\rightarrow\) Lady bug - Bird \(\rightarrow\) Hawk
(b) Cyanobacteria \(\rightarrow\) Shrim\(\rightarrow\) Small fish \(\rightarrow\) Fish eating bird - Snake
(c) Plant\(\rightarrow\)Rat \(\rightarrow\)Snake \(\rightarrow\) Meerkat\(\rightarrow\)Lion
(d) Phytoplankton \(\rightarrow\) Zooplankton \(\rightarrow\)Shellfish\(\rightarrow\)Fish \(\rightarrow\)Shark
(iv) Which of the following pyramids is always upright?

(a) Pyramid of number	(b) Pyramid of biomass
(c) Pyramid of energy	(d) Both (a) and (c)

(v) Refer to the given table

Trophic level	Number of organisms	Energy in trophic level (arbitrary units)
W	100	10,000
X	1	100
Y	1000	100,000
Z	10	1000

Which of the following food chains is correct regarding the given data?

(a) W \(\rightarrow\) X\(\rightarrow\) Y \(\rightarrow\) Z	(b) Y\(\rightarrow\) W \(\rightarrow\) Z\(\rightarrow\) X
(c) W \(\rightarrow\)Z \(\rightarrow\)X\(\rightarrow\) Y	(d) Y\(\rightarrow\)X\(\rightarrow\) Z\(\rightarrow\)W

2)
Various components of an ecosystem maintain a balance in nature. Disturbance in any component of the environment cause an imbalance. One of the main environmental problem caused by human activities is global warming. Global warming is a phenomenon caused by the increasing concentration of greenhouse gases in the atmosphere resulting due to enhanced greenhouse effect.
(i) Refer to the given pie chart showing the contribution of different gases to global warming.

Identify gases P, Q, Rand S and select the incorrect statement regarding them.
(a) P could be a gas that increases in atmosphere due to excessive use offossil fuel.
(b) Q could be a gas produced by complete combustion of biomass.
(c) R could be synthetic gaseous compounds used as refrigerants in air conditioners and refrigerators.
(d) S could be a gas produced by combustion of nitrogen rich fuel.
(ii) What could not be a source of gas Q given in the above pie chart?

(a) Flooded paddy field (b) Cattle

(c) Jet fuel (d) Marshes

(iii) If there is no CO₂ in the atmosphere, then what will be the most likely consequence of this on the temperature of earth?
(a) The temperature remain unchanged as it depends upon the oxygen content of the atmosphere.
(b) The temperature would increase as less greenhouse gases will be absorbed by CO₂
(c) The temperature would decrease as CO₂ is the principal greenhouse gas.
(d) None of these
(iv) Study carefully the following figure representing greenhouse effect.

Select the correct statement regarding this.
(a) Much of the long wavelength infrared radiations re-radiated by the earth's surface are absorbed by the atmospheric greenhouse gases.
(b) CO₂ , CH₄ , CFCs and N₂O are the gases which are responsible for greenhouse effect.
(c) The atmosphere is transparent to the incoming short-wavelength radiations and is translucent to the long-wavelength infra-red radiations.
(d) All of these

(v) Greenhouse effect is due to

(a) accumulation of O₃ and depletion of CO₂ (b) accumulation of both O₃ and CO₂

(c) accumulation of CO₂ and depletion of O₃ (d) presence of green plants on the earth

3)

Disposal of waste should be done scientifically. Solid wastes, i.e., paper, plastics, metals, etc., can be recycled by sending them to respective recycling units. For instance, paper is sent for recycling into special paper mills; broken plastic ie.g., plastic bags, buckets, bowls, dishes, mugs, disks, etc.) are sent to plastic processing factories where these are melted and then remoulded; waste metals are sent to specific metal industries for recycling. Industrial wastes are treated in special plants where valuable wastes are recycled. Certain wastes are mixed to generate useful materials. For instance, molten plastic is mixed with asphalt and the material is used for making roads. Household waste, chemical waste and hospital waste are generally disposed offby an incineration process
(i) What does A represent in the given figure showing an incinerator?

(a) Stolid wase

(b) Fire

(c)Ash

(d) None of these

(ii) Which of the following statements regarding incineration is incorrect?
(a) It is the process of waste disposable by keeping waste at low temperature to stop enzymatic activity.
(b) Household waste, chemical waste and hospital waste are generally disposed by this method.
(c) Disposing waste by using this method generates carbon dioxide and water vapour.
(d) It involves aerobic burning of the combustible waste at high temperature
(iii) In the following groups of material which group contains only recyclable materials?
I. Wood, paper, fruit pulp
II. Plastic bottle, used aluminium foil, glass jug
III. Paper, metal key, plastic mug

(a) I and II only	(c) III only
(b) II and III only	(d) I, II and III

(iv) Incineration and pyrolysis are two methods of waste disposal done at high temperature. The two differs from each other as in later
(a) aerobic burning occurs
(b) chemical energy and chemical constituents are the end products
(c) ashes are the end products
(d) medical wastes are burnt with clinkers as the end product.
(v) The committee members of Robin's society placed two bins-green coloured and blue coloured in their premises for collection of garbage.
Given is the list of few solid wastes generated in his society

Paper cup, credit card, fruit and vegetables peels, cardboard, metal rod, aluminium foil, plastic key chain, pencil, glass sheet

Segregate the wastes in their respective bins and select the correct option.

Green bin	Blue bin
(a) Paper cup, credit card, pencil	Fruit and vegetable peels, cardboard, metal rod, aluminium foil, plastic key chain, glass sheet
(b) Paper cup, fruits and vegetables peels, cardboard,pencil	Credit card, metal rod, aluminium foil, plastic key chain, glass sheet
(c) Fruit and vegetables peels, cardboard, glass sheet,paper cup	Credit card, metal rod, aluminium foil, plastic key chain, pencil
(d) Credit card, metal rod, aluminium foil, glass sheet	Paper cup, fruits and vegetables peels, cardboard, plastic key chain, pencil

4)
A group of ecologists studied and monitored the change in population of three animal species X, Y and Z over a period of ten years. During their research, they found that a new animal species W appeared in the area and its population was also monitored.

(I) Which animal species will unlikely to be alive in 10 years without some intervention?

a) W (b) X

(c) Y (d) Z

(ii) Which of the following species is most likely be the food source of W?

(a) X (b) Y

(c) Z (d) Both X and Z

(iii) What will be the likely consequence if population of X completely declines?

(a) Populations of W, Y and Z also declines (b) Population of Y declines only.

(c) Population of Z remains unchanged. (d) Population of Z increases.

(iv) What would be the most probable reason for the constant population of Z?
(a) There is plenty of food available for Z.
(b) There is no predator of Z in the community.
(c) Ratio of death rate and birth rate is nearly equal in the population of Z.
(d) There is more number of preys for Z in the community.
(v) What could be the reason for declining of X?
(a) There could be more than one predator of X prevailing in the community.
(b) There is food scarcity for X.
(c) More number of prey species are present in the community for X.
(d) Both (a) and (b)
5)
Food web is a network of food chains which become interconnected at various trophic levels so as to form a number of feeding connections amongst different organisms of a biotic community. Different food webs operate in different ecosystems. One such food web operating in an ecosystem is given ahead. Study it carefully and answer the following.

(i) What is the primary energy input in this food web?

(a) Oak tree (b) Oak blossoms (c) Sunlight (d) Oak leaves

(ii) How many food chains are operating in the given food web?

(a) 10 (b) 12 (c) 16 (d) 14

(iii) When a new species 'X' was introduced into the community, the population of toads rose and population of skunks fell over the subsequent two weeks. Species 'X' is most likely to be

(a) another herbivore like toad (b) a predator of insects only

(b) a predator of insects only (d) a predator of skunks and prey of the toad

(iv) Which of the following organisms in the food web passes most of its energy to the subsequent trophic levels?

(a) Bear (b) Wolf (c) Bee (d) Oak tree

(v) Which organisms would be most affected if the oak tree fails to flower?

(a) Mice and insects (b) Birds and bees

(c) Deer and mice (d) Insects and wolves

CBSE 10th Standard Science Subject Magnetic Effects of Electric Current Chapter Case Study Questions With Solution 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)
An insulated copper wire wound on a cylindrical cardboard tube such that its length is greater than its diameter is called a solenoid. When an electric current is passed through the solenoid, it produces a magnetic field around it. The magnetic field produced by a current-carrying solenoid is similar to the magnetic field produced by a bar magnet. The field lines inside the solenoid are in the form of parallel straight lines. The strong magnetic field produced inside a current-carrying solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the solenoid. The strength of magnetic field produced by a current carrying solenoid is directly proportional to the number of turns and strength of current in the solenoid.
(i) The strength of magnetic field inside a long current -carrying straight solenoid is
(a) more at the ends than at the centre
(b) minimum in the middle
(c) same at all points
(d) found to increase from one end to the other.
(ii) The north-south polarities of an electromagnet can be found easily by using

(a) Fleming's right-hand rule (b) Fleming's left-hand rule

(c) Clock face rule (d) Left-hand thumb rule

(iii) For a current in a long straight solenoid N-and S-poles are created at the two ends.
Among the following statements, the incorrect statement is
(a) The field lines inside the solenoid are in the form of straight lines which indicates that the magnetic field is the same at all points inside the solenoid.
(b) The strong magnetic field produced inside the solenoid can be used to magnetise a piece of magnetic material like soft iron, when placed inside the coil.
(c) The pattern of the magnetic field associated with the solenoid is different from the pattern of the magnetic field around a bar magnet.
(d) The N- and S-poles exchange position when the direction of current through the solenoid is reversed.
(iv) A long solenoid carrying a current produces a magnetic field B along its axis. If the current is double and the number of turns per cm is halved, then new value of magnetic field is

(a) B (b) 2B (c) 4B (d) B/2

(v) A soft iron bar is enclosed by a coil of insulated copper wire as shown in figure. When the plug of the key is closed, the face B of the iron bar marked as

(a) N-pole (b) S-pole

(c) N-pole if current is large (d) S-pole if current is small
2)
A magnetic field is described by drawing the magnetic field lines. When a small north magnetic pole is placed in the magnetic field created by a magnet, it will experience a force. And if the north pole is free, it will move under the influence of magnetic field. The path traced by a north magnetic pole free to move under the influence of a magnetic field is called a magnetic field line. Since the direction of magnetic field line is the direction of force on a north pole, so the magnetic field lines always begin from the N-pole of a magnet and end on the S-pole of the magnet. Inside the magnet, however the direction of magnetic field lines is from the S-pole of the magnet to the N-pole of the magnet. Thus, the magnetic field lines are closed curves. When a small compass is moved along a magnetic field line, the compass needle always sets itself along the line tangential to it. So, a line drawn from the south pole of the compass needle to its north pole indicates the direction of the magnetic field at that point.

(i) The magnetic field lines
(a) intersect at right angle to one another
(b) intersect at an angle of 45° to each other
(c) do not cross one another
(d) cross at an angle of 60° to one another.
(ii) A strong bar magnet is placed vertically above a horizontal wooden board. The magnetic lines of force will be
(a) only in horizontal plane around the magnet
(b) only in vertical plane around the magnet
(c) in horizontal as well as in vertical planes around the magnet
(d) in all the planes around the magnet.
(iii) Magnetic field lines can be used to determine
(a) the shape of the magnetic field
(b) only the direction of the magnetic field
(c) only the relative strength of the magnetic field
(d) both the direction and the relative strength of the magnetic field.
(iv) The magnetic field lines due to a bar magnet are correctly shown in figure

(v) Which of the following is not true about magnetic field lines?
(a) Magnetic field lines are the closed and continuous curve.
(b) No two field lines can cross each other.
(c) Crowdness of field lines represents the strength of magnetic field.
(d) The direction of field lines is from the north pole to the south pole inside a bar magnet.
3)
Andre Marie Ampere suggested that a magnet must exert an equal and opposite force on a current carrying conductor, which was experimentally found to be true. But we know that current is due to charges in motion. Thus, it is clear that a charge moving in a magnetic field experience a force, except when it is moving in a direction parallel to it. If the direction of motion is perpendicular to the direction of magnetic field, the magnitude of force experienced depends on the charge, velocity (v), strength of magnetic field (B), and sine of the angle between v and B. Direction of magnetic force is given by Fleming's left hand rule.

(i) If an electron is travelling horizontally towards east. A magnetic field in vertically downward direction exerts a force on the electron along

(a) east (b) west (c) north (d) south

(ii) If a charged particle is moving along a magnetic field line. The magnetic force on the particle is

(a) along its velocity (b) opposite to its velocity

(c) perpendicular to its velocity (d) zero

(iii) A magnetic field exerts no force on
(a) a stationary electric charge
(b) a magnet
(c) an electric charge moving perpendicular to its direction
(d) an unmagnetised iron bar
(iv) A uniform magnetic field exists in the plane of paper pointing from left to right as shown in figure. In the field an electron and a proton move as shown. The electron and the proton experience

(a) forces both pointing into the plane of paper
(b) forces both pointing out of the plane of paper
(c) forces pointing into the plane of paper and out of the plane of paper, respectively
(d) force pointing opposite and along the direction of the uniform magnetic field respectively
(v) An electron beam enters a magnetic field at right angles to it as shown in the figure. The direction of force acting on the electron beam will be

(a) to the left (b) to the right (c) into the page (d) out of the page
4)
A current carrying wire produces magnetic field around it. The phenomena in which an electromotive force and current (if the conductor is in the form of a closed circuit) is induced by changing magnetic field (or by passing magnetic field lines) through it is called electromagnetic induction. The emf so developed is called induced emf and current made to flow is called induced current. The cause of induced emf carried out by Faraday and Henry. It can be concluded that the induced current flows in a conductor as long as the magnetic lines of force change within the conductor. In case of relative motion i.e., motion of coil w.r.t to magnet or vice versa, the direction of the current flowing in the conductor is determined by the direction of the relative motion of the conductor with respect to the magnetic field. The induced emf or current is directly proportional to the rate of change in magnetic field.

(i) A student connects a coil of wire with a sensitive galvanometer as shown in figure. He will observe the deflection in the galvanometer if bar magnet is

(a) placed near one of the faces of the coil and parallel to the axis of the coil
(b) placed near one of the faces of the coil and perpendicular to the axis of the coil
(c) placed inside the coil
(d) moved towards or away from the coil parallel to the axis of the coil.
(ii) A conducting rod AB moves across two magnets as shown in figure and the needle in the galvanometer deflects momentarily. What is the name of this physical phenomenon?

(a) Electromagnetism (b) Induced magnetism

(c) Electromagnetic induction (d) Static induction

(iii) A bar magnet is pushed steadily into a long solenoid connected to a sensitive meter.

Which of the following would affect the magnitude of the deflection of the meter?
(a) How fast the magnet is pushed into the coil.
(b) The direction in which the coil is wound.
(c) The end of the solenoid the magnet enters.
(d) The pole of the magnet enters the coil first.
(iv) What is the condition of an electromagnetic induction?
(a) There must be a relative motion between galvanometer and coil of wire.
(b) There must be a relative motion between galvanometer and a magnet.
(c) There must be a relative motion between galvanometer and electric motor.
(d) There must be a relative motion between the coil of wire and a magnet.
(v) An induced emf is produced when a magnet is plunged into a coil. The magnitude of induced emf does not depend on

(a) the number of turns in the coil (b) the speed with which the magnet is moved

(c) the strength of the magnet (d) the resistivity of the material of the coil
5)
An electric motor is a rotating device that converts electrical energy into mechanical energy. Electric motor is used as an important component in electric fans, refrigerators, mixers, washing machines, computers, MP3 players, etc.

An electric motor consists of a rectangular coil ABCD of insulated copper wire. The coil is placed between the two poles of a magnetic field such that the arm AB and CD are perpendicular to the direction of the magnetic field. The ends of the coil are connected to the two halves P and Q of a split ring. The inner sides of these halves are insulated and attached to an axle. The external conducting edges of P and Q touch two conducting stationary brushes X and Y,respectively, as shown in the figure. Commercial motors use an electromagnet in place of a permanent magnet, a large number of turns of conducting wire in the current carrying coil and a soft iron core on which the coil is wound.
(i) Choose incorrect statement from the following regarding split rings.
(a) Split rings are used to reverse the direction of current in coil.
(b) Split rings are also known as commutator.
(c) Split ring ii a discontinuous or a broken ring.
(d) Both (a) and (b)
(ii) Which of the following has no effect on the size of the turning effect on the coil of an electric motor?

(a) The amount of the current in the coil (b) The direction of the current in the coil.

(c) The number of turns in the coil. (d) The strength of the magnetic field

(iii) When current is switched ON, an electric fan converts

(a) mechanical energy to chemical energy (b) electrical energy to mechanical energy

(c) chemical energy to mechanical energy (d) mechanical energy to electrical energy.

(iv) In an electric motor, device that makes contact with the rotating rings and through them to supply current to coil is

(a) axle (b) brushes (c) coil (d) split rings.

(v) In an electric motor, the direction of current in the coil changes once in each

(a) two rotations (b) one rotation (c) half rotation (d) one-fourth rotation

CBSE 10th Standard Science Subject Electricity Chapter Case Study Questions With Solution 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

The rate of flow of charge is called electric current. The SI unit of electric current is Ampere (A). The direction of flow of current is always opposite to the direction of flow of electrons in the current.
The electric potential is defined as the amount of work done in bringing a unit positive test charge from infinity to a point in the electric field. The amount of work done in bringing a unit positive test charge from one point to another point in an electric field is defined as potential difference.
\(\begin{equation} V_{A B}=V_{B}-V_{A}=\frac{W_{B A}}{q} \end{equation}\)
The SI unit of potential and potential difference is volt.
(i) The 2 C of charge is flowing through a conductor in 100 rns, the current in the circuit is

(a) 20 A	(b) 2 A
(c) 0.2 A	(d) 0.02 A

(ii) Which of the following is true?
(a) Current flows from positive terminal ofthe cell to the negative terminal of the cell outside the cell.
(b) The negative charge moves from lower potential to higher potential.
(c) The direction of flow of current in same as the direction of flow of positive charge.
(d) All of these
(iii) The potential difference between the two terminals of a battery, if 100 joules of work is required to transfer 20 coulombs of charge from one terminal of the battery to other is

(a) 50 V	(b) -5 V
(c) 0.5 V	(d) 500 V

(iv) The number of electrons flowing per second in a conductor if 1A current is passing through it

(a) 6.25 x 10²⁰	(b) 6.25 x 10¹⁹
(c) 6.25 X 10¹⁸	(d) 6.25 x 10^-19

(v) The voltage can be written as

(a) Work done x charge x time	(b) \(\begin{equation} \frac{\text { Work done }}{\text { Current } \times \text { time }} \end{equation}\)
(c) \(\begin{equation} \frac{\text { Work done } \times \text { time }}{\text { Current }} \end{equation}\)	(d) Work done x charge

2)

The relationship between potential difference and current was first established by George Simon Ohm called Ohm's law. According to this law, the current through a metallic conductor is proportional to the potential difference applied between its ends, provided the temperature remain constant i.e. I \(\begin{equation} \propto \end{equation}\) V or V = IR; where R is constant for the conductor and it is called resistance of the conductor. Although Ohm's law has been found valid over a large class of materials, there do exist materials and devices used in electric circuits where the proportionality of V and I does not hold.
(i) If both the potential difference and the resistance in a circuit are doubled, then

(a) current remains same	(b) current is doubled
(c) current is halved	(d) current is quadrupled

(ii) For a conductor, the graph between V and I is there. Which one is the correct?

(a)	(b)
(c)	(d)

(iii) The slope of V - I graph (V on x-axis and I on y-axis) gives

(a) resistance	(b) reciprocal of resistance
(c) charge	(d) reciprocal of charge.

(iv) When battery of 9 V is connected across a conductor and the current flows is 0.1 A, the resistance is

(a) 9 \(\begin{equation} \Omega \end{equation}\)	(b) 0.9 \(\begin{equation} \Omega \end{equation}\)
(c) 90 \(\begin{equation} \Omega \end{equation}\)	(d) 900 \(\begin{equation} \Omega \end{equation}\)

(v) By increasing the voltage across a conductor, the

(a) current will decrease	(b) resistance will increase
(c) current will increase	(d) resistance will decrease.

3)

The obstruction offered by a conductor in the path of flow of current is called resistance. The SI unit of resistance is ohm (\(\begin{equation} \Omega \end{equation}\)). It has been found that the resistance of a conductor depends on the temperature of the conductor. As the temperature increases the resistance also increases. But the resistance of alloys like mangnin, constantan and nichrome is almost unaffected by temperature. The resistance of a conductor also depends on the length of conductor and the area of cross-section of the conductor. More be the length, more will be the resistance, more be the area of cross-section, lesser will be the resistance.
(i) Which of the following is not will desired in material being used for making electrical wires?

(a) High melting point	(b) High resistance
(c) High conductivity	(d) None of these

(ii) The V - I graph for two metallic wires A and B is given. What is the correct relationship between their temperatures?

(a) T_A < T_B	(b) T_A > T_B
(c) T_A= T_B	(d) none of these

(iii) Two wires of same material one of length L and area of cross-section A, other is of length 2L and area A/2 . Which of the following is correct?

(a) R₁= R₂	(b) R₁= 4R₂
(c) R₂ = 4R₁	(d) R₁= 2R₂

(iv) For the same conducting wire
(a) resistance is higher in summer
(b) resistance is higher in winter
(c) resistance is same is summer or in winter
(d) none of these
(v) A wire of resistance 20 \(\begin{equation} \Omega \end{equation}\) is cut into 5 equal pieces. The resistance of each part is

(a) 4 \(\begin{equation} \Omega \end{equation}\)	(b) 10 \(\begin{equation} \Omega \end{equation}\)
(c) 100 \(\begin{equation} \Omega \end{equation}\)	(d) 80 \(\begin{equation} \Omega \end{equation}\)

4)

Two or more resistances are connected in series or in parallel or both, depending upon whether we want to increase or decrease the circuit resistance.

The two or more resistances are said to be connected in series if the current flowing through each resistor is same. The equivalent resistance in the series combination is given by
R_s = R₁ + R₂+ R₃
(i) When three resistors are connected in series with a battery of voltage V and voltage drop across resistors is V₁, V₂ and V₃, which of the relation is correct?

(a) V = V₁= V₂= V₃	(b) V = V₁+ V₂ + V₃
(c) V₁ + V₂ + V₃ = 3V	(d) V > V₁ + V₂ + V₃

(ii) When the three resistors each of resistance R ohm, connected in series, the equivalent resistance is

(a) R/2	(b) > R
(c) < R/2	(d) < R

(iii) There is a wire oflength 20 cm and having resistance 20 \(\begin{equation} \Omega \end{equation}\) cut into 4 equal pieces and then joined in series.
The equivalent resistance is

(a) 20 \(\begin{equation} \Omega \end{equation}\)	(b) 4 \(\begin{equation} \Omega \end{equation}\)
(c) 5 \(\begin{equation} \Omega \end{equation}\)	(d) 10 \(\begin{equation} \Omega \end{equation}\)

(iv) In the following circuit, find the equivalent resistance between A and B is (R = 2 \(\begin{equation} \Omega \end{equation}\))

(a) 10 \(\begin{equation} \Omega \end{equation}\)	(b) 5 \(\begin{equation} \Omega \end{equation}\)
(c) 2 \(\begin{equation} \Omega \end{equation}\)	(d) 4 \(\begin{equation} \Omega \end{equation}\)

(v) In the given circuit, the current in each resistor is

(a) 3 A	(b) 6 A
(c) 9 A	(d) 18 A

CBSE 10th Standard Science Subject Electricity Chapter Case Study Questions 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

If two or more resistances are connected in such a way that the same potential difference gets applied to each of them, then they are said to be connected in parallel. The. current flowing through the two resistances in parallel is, however, not the same. When we have two or more resistances joined in parallel to one another, then the same current gets additional paths to flow and the overall resistance decreases. The equivalent resistance is given by \(\begin{equation} \frac{1}{R_{p}}=\frac{1}{R_{1}}+\frac{1}{R_{2}}+\frac{1}{R_{3}} \end{equation}\)

(i) Three resistances, 2 \(\begin{equation} \Omega \end{equation}\) , 6 \(\begin{equation} \Omega \end{equation}\) and 8 \(\begin{equation} \Omega \end{equation}\) are connected in parallel, then the equivalent resistance is
(a) less than 6 \(\begin{equation} \Omega \end{equation}\) but more than 2 \(\begin{equation} \Omega \end{equation}\)
(b) less than 8 \(\begin{equation} \Omega \end{equation}\) but more than 6 \(\begin{equation} \Omega \end{equation}\)
(c) less than 2 \(\begin{equation} \Omega \end{equation}\)
(d) more than 8 \(\begin{equation} \Omega \end{equation}\)
(ii) A wire of resistance 12 \(\begin{equation} \Omega \end{equation}\) is cut into three equal pieces and then twisted their ends together, the equivalent resistance is

(a) \(\begin{equation} \frac{3}{8} \Omega \end{equation}\)	(b) \(\begin{equation} \frac{4}{3} \Omega \end{equation}\)
(c) \(\begin{equation} \frac{3}{4} \Omega \end{equation}\)	(d) \(\begin{equation} \frac{5}{6} \Omega \end{equation}\)

(iii) Three resistances are connected as shown. The equivalent resistance between A and B is

(a) \(\begin{equation} \frac{2}{3} \Omega \end{equation}\)	(b) \(\begin{equation} \frac{3}{2} \Omega \end{equation}\)
(c) \(\begin{equation} \frac{4}{3} \Omega \end{equation}\)	(d) \(\begin{equation} \frac{3}{4} \Omega \end{equation}\)

(iv) Which of the following relation is correct?

(a) I₁= 2I₂ = 3I₃	(b) I₁= 4I₂ = 3I₃
(c) 2I₁= I₂ = 3I₃	(d) 3I₁= 2I₂ = I₃

(v) Find the current in each resistance.

(a) 1 A	(b) 2 A
(c) 3 A	(d) 0.25 A

2)

Several resistors may be combined to form a network. The combination should have two end points to connect it with a battery or other circuit elements. When the resistances are connected in series, the current in each resistance is same but the potential difference is different in each resistor. When the resistances are connected in parallel, the voltage drop across each resistance is same but the current is different in each resistor.
(i) The household circuits are connected in

(a) series combination	(b) parallel combination
(c) both (a) and (b)	(d) none of these

(ii) The two wires of each of resistance R, initially connected in series and then in parallel. In the graph it shows the resistance in series and in parallel. Which of the following is correct?

(a) A denotes parallel combination.
(b) B denotes series combination.
(c) A denotes series combination and B denotes parallel combination.
(d) None of these.
(iii) The equivalent resistance of r₁ and r₂, when connected in series is R₁ and when they are connected in parallel is R₂. Then the ratio is

(a) \(\begin{equation} \frac{r_{1}}{r_{2}} \end{equation}\)	(b) \(\begin{equation} \frac{r_{1}+r_{2}}{r_{1} r_{2}} \end{equation}\)
(c) \(\begin{equation} \frac{\left(r_{1}+r_{2}\right)^{2}}{r_{1} r_{2}} \end{equation}\)	(d) \(\begin{equation} \frac{r_{1} r_{2}}{2 r_{1}+2 r_{2}} \end{equation}\)

(iv) The equivalent resistance between A and B is

(a) 6 \(\begin{equation} \Omega \end{equation}\)	(b) 9 \(\begin{equation} \Omega \end{equation}\)
(c) 3 \(\begin{equation} \Omega \end{equation}\)	(d) 12 \(\begin{equation} \Omega \end{equation}\)

(v) Two resistances 10 \(\begin{equation} \Omega \end{equation}\) and 3 \(\begin{equation} \Omega \end{equation}\)are connected in parallel across a battery. If there is a current of 0.2 A in 10 .Q resistor, the voltage supplied by battery is

(a) 2 V	(b) 4 V
(c) 1 V	(d) 8 V

3)
The heating effect of current is obtained by transformation of electrical energy in heat energy. Just as mechanical energy used to overcome friction is covered into heat, in the same way, electrical energy is converted into heat energy when an electric current flows through a resistance wire. The heat produced in a conductor, when a current flows through it is found to depend directly on (a) strength of current (b) resistance of the conductor (c) time for which the current flows.
The mathematical expression is given by H = I²Rt.
The electrical fuse, electrical heater, electric iron, electric geyser etc. all are based on the heating effect of current.
(i) What are the properties of heating element?
(a) High resistance, high melting point
(b) Low resistance, high melting point
(c) Low resistance, high melting point
(d) Low resistance, low melting point.
(ii) What are the properties of electric fuse?
(a) Low resistance, low melting point
(b) High resistance, high melting point.
(c) High resistance, low melting point
(d) Low resistance, high melting point
(iii) When the current is doubled in a heating device and time is halved, the heat energy produced is

(a) doubled (b) halved

(c) four times (d) one fourth times

(iv) A fuse wire melts at 5 A. It is is desired that the fuse wire of same material melt at 10 A. The new radius of the wire is

(a) 4 times (b) 2 times

(c) \(\begin{equation} \frac{1}{2} \text { times } \end{equation}\) (d) \(\begin{equation} \frac{1}{4} \text { times } \end{equation}\)

(v) When a current of 0.5 A passes through a conductor for 5 min and the resistance of conductor is 10 \(\begin{equation} \Omega \end{equation}\), the amount of heat produced is

(a) 250 J (b) 5000J

(c) 750J (d) 1000J

4)

The electrical energy consumed by an electrical appliance is given by the product of its power rating and the time for which it is used. The SI unit of electrical energy is Joule. Actually, Joule represents a very small quantity of energy and therefore it is inconvenient to use where a large quantity of energy is involved. So for commercial purposes we use a bigger unit of electrical energy which is called kilowatt hour. 1 kilowatt-hour is equal to 3.6 x 106 joules of electrical energy.
(i) The energy dissipated by the heater is E. When the time of operating the heater is doubled, the energy dissipated is

(a) doubled	(b) half
(c) remains same	(d) four times

(ii) The power of a lamp is 60 W The energy consumed in 1 minute is

(a) 360J	(b) 36J
(c) 3600J	(d) 3.6 J

(iii) The electrical refrigerator rated 400 W operates 8 hours a day. The cost of electrical energy is \(\begin{equation} ₹ \end{equation}\)5 per kWh. Find the cost of running the refrigerator for one day?

(a) \(\begin{equation} ₹ \end{equation}\)32	(b) \(\begin{equation} ₹ \end{equation}\)16
(c) \(\begin{equation} ₹ \end{equation}\)8	(d) \(\begin{equation} ₹ \end{equation}\)4

(iv) Calculate the energy transformed by a 5 A current flowing through a resistor of 2 \(\begin{equation} \Omega \end{equation}\) for 30 minutes?

(a) 90 kJ	(b) 80 kJ
(c) 60 kJ	(d) 40 kJ

(v) Which of the following is correct?
(a) 1 watt hour = 3600 J
(b) lkWh = 36x10⁶J
(c) Energy (in kWh) = power (in W) x time (in hr)
(d) \(\begin{equation} \text { Energy (in kWh) }=\frac{V(\text { volt }) \times I(\text { ampere }) \times t(\text { sec })}{1000} \end{equation}\)

CBSE 10th Standard Science Subject Human Eye and the Colourful World Chapter Case Study Questions With Solution 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

A prism is a transparent refracting medium bounded by two plane surfaces inclined to each other at a certain angle. The refraction of light through a prism follows the laws of refraction. In the prism, refraction takes place on its refracting surface it means when the light enters the prism and when the light leaves the prism. The refraction through a prism is shown. Here, A is the angle of prism, \(\angle\)i is the angle of incidence of the face AB and \(\angle\)e is the angle of emergence at other face AC.

The incident ray suffers a deviation or bending through an angle \(\begin{equation} \delta \end{equation}\) due to the refraction through prism. This angle is called angle of deviation as shown in figure.
\(\angle\)i + \(\angle\)e = \(\angle\)\(\begin{equation} \delta \end{equation}\) + \(\angle\)A
(i) The angle between the two refracting surfaces of a prism is called

(a) angle of prism	(b) angle of incidence
(c) angle of deviation	(d) angle of emergence

(ii) The angle between the incident ray and the emergent ray is called

(a) angle of emergence	(b) angle of deviation
(c) angle of incidence	(d) none of these

(iii) When a ray is refracted through a prism, then

(a) \(\angle\)i=\(\angle\)\(\begin{equation} \delta \end{equation}\)	(b) \(\angle\) i=\(\angle\)e+\(\angle\)\(\begin{equation} \delta \end{equation}\)
(c) \(\angle\)\(\begin{equation} \delta \end{equation}\)= \(\angle\)e	(d) \(\angle\)i > \(\angle\)r

(iv) The angle of deviation depends on

(a) refractive index of prism	(b) angle of incidence
(c) both (a) and (b)	(d) none of these

(v) The rectangular surfaces of a prism are known as

(a) reflecting surfaces	(b) dispersing surfaces
(c) refracting surfaces	(d) none of these.

2)
When white light is incident on one refracting surface of the prism, the light splits up into constituent colours violet, indigo, blue, green, yellow, orange and red. The process of splitting of white light into its seven constituent colours is called dispersion. When the dispersed white light is made to fall on a screen, we get the band of seven colours is called the spectrum of white light. Red colour bends the least on passing through the prism and violet colour bends through maximum angle on passing through the prism.

(i) The splitting of white light can be done by

(a) lens (b) prism

(c) mirror (d) none of these

(ii) Which property of light is used by prism to form a spectrum?

(a) Reflection (b) Refraction

(c) Dispersion (d) Scattering

(iii) Which of the following dispersion is correct?

(a) (b)

(c) (d)

(iv) When a red light passes through a prism, it
(a) will not split
(b) will split into seven colours
(c) will split into white colour
(d) will split into many different colours.
(v) The spectrum produced by the white light by a prism is called

(a) pure spectrum (b) impure spectrum

(c) monochromatic spectrum (d) none of these.
3)
Light of all the colour travel at the same speed in vacuum for all wavelengths. But in any transparent medium
(glass or water), the light of different colours travel with different speeds for different wavelength that means
that the refractive index of a particular medium is different for different wavelength. As there is a difference in
their speeds, the light of different colour bend through different angles. The speed of violet colour is maximum and the speed of red colour is minimum in glass so, the red light deviates least and violet colour deviates most.
Hence, higher the wavelength of a colour of light, smaller the refractive index and less is the bending of light.
\(\begin{equation} \lambda \end{equation}\)r > \(\begin{equation} \lambda \end{equation}\)v and r_n < v_n, \(\begin{equation} v=\frac{c}{\lambda} . \end{equation}\)
(i) Which of the following statements is correct regarding the propagation of light of different colours of white light in air?
(a) Red light moves fastest.
(b) Blue light moves faster than green light.
(c) All the colours of the white light move with the same speed.
(d) Yellow light moves with the mean speed as that of the red and the violet light.
(ii) Which of the following is the correct order of wavelength?

(a) Red> Green> Yellow (b) Red> Violet> Green

(c) Yellow> Green> Violet (d) Red> Yellow> Orange

(iii) Which of the following is the correct order of speed of light in glass?

(a) Red> Green> Blue (b) Blue> Green> Red

(c) Violet> Red> Green (d) Green> Red> Blue

(iv) Which colour which has maximum frequency

(a) Red (b) Violet

(c) Blue (d) Green

(v) Which of the following is the correct order of angle of deviation?

(a) Red> Green> Blue (b) Blue> Yellow> Orange

(c) Orange> Red> Green (d) Blue> Green> Violet
4)
The spreading of light by the air molecules is called scattering oflight. The light having least wavelength scatters more. The sun appears red at sunrise and sunset, appearance of blue sky it is due to the scattering of light. The colour of the scattered light depends on the size of particles. The smaller the molecules in the atmosphere scatter smaller wavelengths of light. The amount of scattering of light depends on the wavelength of light. When light from sun enters the earth's atmosphere, it gets scattered by the dust particles and air molecules present in the atmosphere. The path of sunlight entering in the dark room through a fine hole is seen because of scattering of the sun light by the dust particles present in its path inside the room.
(i) To an astronaut in a spaceship, the colour of earth appears

(a) red (b) blue

(c) white (d) black

(ii) At the time of sunrise and sunset, the light from sun has to travel.
(a) longest distance of atmosphere
(b) shortest distance of atmosphere
(c) both (a) and (b)
(d) can't say
(iii) The colour of sky appears blue, it is due to the
(a) refraction oflight through the atmosphere
(b) dispersion of light by air molecules
(c) scattering of light by air molecules
(d) all of these.
(iv) At the time of sunrise and sunset
(a) Blue colour scattered and red colour reaches our eye
(b) Red colour scattered and blue colour reaches our eye
(c) Green and blue scattered and orange reaches our eye
(d) None of these
(v) The danger signs made red in colour, because
(a) the red light can be seen from farthest distance
(b) the scattering of red light is least
(c) both (a) and (b)
(d) none of these
5)
Atmospheric refraction is the phenomenon of bending of light on passing through earth's atmosphere. As we move above the surface of earth, density of air goes on decreasing. Local conditions like temperature etc. also affect the optical density of earth's atmosphere. On account of atmospheric refraction, stars seen appear higher than they actual are; advanced sunrise; delayed sunset, oval appearance of the sun at sunrise and sunset; stars twinkle, planets do not.
(i) Due to atmospheric refraction, apparent length of the day

(a) increases (b) decreases

(c) remains the same (d) all of these

(ii) Apparent position of the star appears raised due to

(a) atmospheric refraction (b) scattering of light

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

(iii) The sun appears oval shaped or flattened due to

(a) dispersion (b) scattering

(c) atmospheric refraction (d) cannot say

(iv) Twinkling of stars and non-twinkling of planets is accounted for by

(a) scattering of light (b) dispersion of light

(c) atmospheric refraction (d) none of these

(v) In absence of atmosphere, the colour of sky appears

(a) blue (b) black

(c) red (d) yellow

CBSE 10th Standard Science Subject Light Reflection and Refraction Chapter Case Study Questions With Solution 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)
The curved surface of a spoon can be considered as a spherical mirror. A highly smooth polished surface is called mirror. The mirror whose reflecting surface is curved inwards or outwards is called a spherical mirror. Inner part works as a concave mirror and the outer bulging part acts as a convex mirror. The center of the reflecting surface of a mirror is called pole and the radius of the sphere of which the mirror is formed is called radius of curvature.
(i) When a concave mirror is held towards the sun and its sharp image is formed on a piece of carbon paper for some time, a hole is burnt in the carbon paper. What is the name given to the distance between the mirror and carbon paper?

(a) Radius of curvature (b) Focallength

(c) Principal focus (d) Principal axis

(ii) The distance between pole and focal point of a spherical mirror is equal to the distance between

(a) pole and center of curvature (b) focus point and center of curvature

(c) pole and object (d) object and image

(iii) The focal length of a mirror is 15 cm. The radius of curvature is

(a) 15 cm (b) 30 cm

(c) 45 cm (d) 60 cm

(iv) The normal at any point on the mirror passes through

(a) focus (b) pole

(c) center of curvature (d) any point

(v) In a convex spherical mirror, reflection of light takes place at

(a) a flat surface (b) a bent-in surface

(c) a bulging-out surface (d) an uneven surface
2)
The spherical mirror forms different types of images when the object is placed at different locations.
When the image is formed on screen, the image is real and when the image does not form on screen, the image is virtual. When the two reflected rays meet actually, the image is real and when they appear to meet, the image is virtual.
A concave mirror always forms a real and inverted image for different positions of the object. But if the object is placed between the focus and pole, the image formed is virtual and erect.
A convex mirror always forms a virtual, erect and diminished image. A concave mirror is used as doctor's head mirror to focus light on body parts like eyes, ears, nose etc., to be examined because it can form erect and magnified image of the object. The convex mirror is used as a rear view mirrors in automobiles because it can form an small and erect image of an object.
(i) When an object is placed at the centre of curvature of a concave mirror, the image formed is

(a) larger than the object (b) smaller than the object

(c) same size as that of the object (d) highly enlarged.

(ii) No matter how far you stand from a mirror, your image appears erect. The mirror is likely to be

(a) plane (b) concave

(c) convex (d) either plane or convex.

(iii) A child is standing in front of a magic mirror. She finds the image of her head bigger, the middle portion of her body of the same size and that of the legs smaller. The following is the order of combinations for the magic mirror from the top.

(a) Plane, convex and concave (b) Convex, concave and plane

(c) Concave, plane and convex (d) Convex, plane and concave

(iv) To get an image larger than the object, one can use
(a) convex mirror but not a concave mirror
(b) a concave mirror but not a convex mirror
(c) either a convex mirror or a concave mirror
(d) a plane mirror.
(v) A convex mirror has wider field of view because
(a) the image formed is much smaller than the object and large number of images can be seen
(b) the image formed is much closer to the mirror
(c) both (a) and (b)
(d) none of these.
3)
The relation between distance of an object from the mirror (u), distance of image from the mirror (v) and the focal length (F) is called mirror formula. This formula is valid in all situations for all spherical mirrors for all positions of the object. The size of image formed by a spherical mirror depends on the position of the object from the mirror. The image formed by a spherical mirror can be bigger than the object, equal to the object or smaller than the object. The size of the image relative to the object is given by the linear magnification (m). Thus, the magnification is given by the ratio of height of image to the height of object. If magnification is negative, image is real and if it is positive, image is virtual.
(i) What is the position of an image when an object is placed at a distance of 20 em from a concave mirror of
focal length 20 cm?

(a) 5 cm (b) 20 cm

(c) 10 cm (d) infinity

(ii) Which of the following ray diagrams is correct for the ray of light incident on a concave mirror as shown in figure?

(a) Figure A
(b) Figure B

(C) Figure C
(d) Figure D

(iii) If the magnification of an image is -2, the characteristic of image will be

(a) real and inverted (b) virtual and enlarged

(c) virtual and inverted (d) real and small

(iv) The mirror formula holds for

(a) concave mirror (b) convex mirror

(c) plane mirror (d) all of these

(v) A parallel beam of light is made to fall on a concave mirror. An image is formed at a distance of7.5 from the mirror. The focal length of the mirror is

(a) 15 cm (b) 7.5 cm

(c) 3.75 cm (d) 10 cm
4)
When the rays of light travels from one transparent medium to another, the path of light is deviated. This phenomena is called refraction of light. The bending of light depends on the optical density of medium through which the light pass.

The speed of light varies from medium to medium. A medium in which the speed of light is more is optically rarer medium whereas in which the speed of light is less is optically denser medium. Whenever light goes from one medium to another, the frequency of light does not change however, speed and wavelength change. It concluded that change in speed of light is the basic cause of refraction.
(i) When light travels from air to glass, the ray of light bends

(a) towards the normal (b) away from normal

(c) anywhere (d) none of these

(ii) A ray of light passes from a medium A to another medium B. No bending of light occurs if the ray of light hits the boundary of medium B at an angle of

(a) 0° (b) 45°

(c) 90° (d) 120°

(iii) When light passes from one medium to another, the frequency of light

(a) increases (b) decreases

(c) remains same (d) none of these

(iv) When light passes from glass to water, the speed of light

(a) increases (b) decreases

(c) remains same (d) first increases then decrease

(v) The bottom of pool filled with water appears to be ______ due to refraction of light

(a) shallower (b) deeper

(c) at same depth (d) empty

CBSE 10th Standard Science Subject Light Reflection and Refraction Chapter Case Study Questions 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)
The refraction oflight on going from one medium to another takes place according to two laws which are known as the laws of refraction of light. These laws are
1. The ratio of sine of angle of incidence to the sine of angle of refraction is always constant for the pair of media in contact.
\(\frac{\sin i}{\sin r}=\mu=\text { constant }\)
This constant is called refractive index of the second medium with respect to the first medium.
Refractive index is also defined as the ratio of speed of light in vacuum to the speed of light in medium.
2. The incident ray, refracted ray and normal all lie in the same plane.
This law is called Snell's law of refraction.
(i) When light travels from air to glass,
(a) angle of incidence > angle of refraction
(b) angle of incidence < angle of refraction
(c) angle of incidence = angle of refraction
(d) can't say
(ii) When light travels from air to medium, the angle of incidence is 45° and angle of refraction is 30°. The refractive index of second medium with respect to the first medium is

(a) 1.41 (b) 1.50

(c) 1.23 (d) 1

(iii) In which medium, the speed of light is minimum?

(a) Air (b) Glass

(c) Water (d) Diamond

(iv) If the refractive index of glass is 1.5 and speed of light in air is 3 x 10⁸ m/s. The speed of light in glass is

(a) 2 x 10⁸ mls (b) 2.9 x 10⁸ mls

(c) 4.5 x 10⁸ mls (d) 3 x 10⁸ mls

(v) Refractive index of a with respect to b is 2. Find the refractive index of b with respect to a.

(a) 0.4 (b) 0.5

(c) 0.25 (d) 2.
2)
A lens is a piece of any transparent material bounded by two curved surfaces. There are two types of lenses convex lens and concave lens.

Convex lens is made up of a transparent medium bounded by two spherical surfaces such that thicker at the middle and thinner at the edges. Concave lens is also made up of a transparent medium such that thicker at the edge and thinner at the middle. The mid point of the lens is called optical centre.
A point on the principal axis, where the incident parallel rays meet or appears to come out after refraction is called focus.
A convex lens converges a parallel beam of light to other side whereas concave lens spreads out.
(i) Which of the following lenses would you prefer to use while reading small letters found in dictionary?
(a) A convex lens of focal length 50 cm
(b) A concave lens of focal length 50 cm
(c) A convex lens of focal length 5 cm
(d) A concave lens of focal length 5 cm
(ii) Which type oflenes are shown in given figure (i) and (ii).

(a) Plano concave, concavo convex
(b) Plano convex, convexo concave
(c) Double concave, concave convex
(d) Convexo concave, double convex
(iii) A small bulb is placed at the focal point of a converging lens. When the bulb is switched on, the lens produces
(a) a convergent beam of light
(b) a divergent beam of light
(c) a parallel beam of light
(d) a patch of coloured light
(iv) The part oflens through which the refraction takes place is called

(a) aperture (b) centre of curvature

(c) principal axis (d) focus

(v) A water drop acts as a

(a) convex lens (b) concave lens

(c) double concave lens (d) none of these
3)
The lenses forms different types of images when object placed at different locations. When a ray is incident parallel to the principal axis, then after refraction, it passes through the focus or appears to come from the focus.When a ray goes through the optical centre of the lens, it passes without any deviation.
If the object is placed between focus and optical center of the convex lens, erect and magnified image is formed. As the object is brought closer to the convex lens from infinity to focus, the image moves away from the convex lens from focus to infinity. Also the size of image goes on increasing and the image is always real and inverted. A concave lens always gives a virtual, erect and diminished image irrespective to the position of the object.
(i) The location of image formed by a convex lens when the object is placed at infinity is

(a) at focus (b) at 2F

(c) at optical center (d) between F and 2F

(ii) When the object is placed at the focus of concave lens, the image formed is

(a) real and smaller (b) virtual and inverted

(c) virtual and smaller (d) real and erect

(iii) The size of image formed by a convex lens when the object is placed at the focus of convex lens is

(a) small (b) point in size

(c) highly magnified (d) same as that of object

(iv) When the object is placed at 2F in front of convex lens, the location of image is

(a) at F (b) at 2 F on the other side

(c) at infinity (d) between F and optical center
4)
The relationship between the distance of object from the lens (u), distance of image from the lens (v) and the focal length (j) of the lens is called lens formula. It can be written as\(\begin{equation} \frac{1}{f}=\frac{1}{v}-\frac{1}{u} \end{equation}\)
The size of image formed by a lens depends on the position of the object from the lens. A lens of short focal length has more power whereas a lens of long focal length has less power. When the lens is convex, the power is positive and for concave lens, the power is negative.
The magnification produced by a lens is the ratio of height of image to the height of object as the size of the image relative to the object is given by linear magnification (m).
When, m is negative, image formed is real and when m is positive, image formed is virtual. If m < 1, size of image is smaller than the object. If m > 1, size of image is larger than the object.
(i) An object 4 cm in height is placed at a distance of 10 cm from a convex lens of focal length 20 cm. The position of image is

(a) - 20 cm (b) 20 cm

(c) -10 cm (d) 10 cm

(ii) In the above question, the size of image is

(a) 16 cm (b) 8 cm

(c) 4 cm (d) 2 cm

(iii) An object is ,placed 50 cm from a concave lens and produces a virtual image at a distance of 10 cm infrontof lens. The focal length of lens is

(a) - 25 cm (b) -12.5 cm

(c) 12.5 cm (d) 10 cm

(iv) A convex lens forms an image of magnification -2 of the height of image is 6 cm, the height of object is

(a) 6 cm (b) 4 cm

(c) 3 cm (d) 2 cm

(v) A concave lens offocallength 5 ern, the power oflens is

(a) 20D (b) -20D

(c) 90D (d) -5 D

CBSE 10th Standard Science Subject Heredity and Evolution Chapter Case Study Questions With Solution 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)
Sex determination is the method by which distinction between males and females is established in a species. The sex of an individual is determined by specific chromosomes. These chromosomes are called sex chromosomes or allosomes. X and Y chromosomes are called sex chromosomes. The normal chromosomes other than the sex chromosomes of an individual are known as autosomes.
(i) In XX-XO type of sex determination
(a) females produce two different types of gametes
(b) males produce two different types of gametes
(c) females produce gametes with Y chromosome
(d) males produce gametes with Y chromosome.
(ii) A couple has six daughters. What is the possibility of their having a girl next time?

(a) 10% (b) 50%

(c) 90% (d) 100%

(iii) Number of autosomes present in liver cells of a human female is

(a) 22 autosomes (b) 22 pairs

(c) 23 autosomes (d) 23 pairs.

(iv) XX-XO type of sex determination and XX-XY type of sex determination are the examples of

(a) male heterogamety (b) female heterogamety

(c) male homogamety (d) both (b) and (c).

(v) Select the incorrect statement.
(a) In male grasshoppers, 50% of sperms have no sex chromosome
(b) Female fruitfly is heterogametic
(c) Human male produces two types of sperms 50% having X chromosome and 50% having Y chromosomes
(d) In turtle, sex determination is regulated by environmental factors.

2)

Gregor Mendel conducted hybridisation experiments on garden peas for seven years and proposed the laws of inheritance in living organisms. He investigated characters in the garden pea plant that were manifested as two opposing traits, e.g., tall or dwarf plants, yellow and green seeds, etc.
(i) Among the seven pairs of contrasting traits in pea plant as studied by Mendel, the number of traits related
to flower, pod and seed respectively were

(a) 2,2,2	(b) 2,2,1
(c) 1,2,2	(d) 1,1,2.

(ii) The colour based contrasting traits in seven contrasting pairs, studied by Mendel in pea plant were

(a) 1	(b) 2
(c) 3	(d) 4.

(iii) Refer to the given table of contrasting traits in pea plants studied by Mendel.

Character	Dominant trait	Recessive trait
(i) Seed colour
(ii) Flower colour
(iii) Pod shape
(iv) Flower position

Which of the given traits is correctly placed?
(a) (i), (ii) and (iii) only
(b) (ii), (iii) and (iv) only
(c) (ii) and (iii) only
(d) (i), (ii), (iii) and (iv)
(iv) Some of the dominant traits studied by Mendel were
(a) round seed shape, green seed colour and axial flower position
(b) terminal flower position, green pod colour and inflated pod shape
(c) violet flower colour, green pod colour and round seed shape
(d) wrinkled seed shape, yellow pod colour and axial flower position.
(v) Which of the following characters was not chosen by Mendel?

(a) Pod shape	(b) Pod colour
(c) Position of flower	(d) Position of pod

3)
Mendel crossed tall and dwarf pea plants to study the inheritance of one gene. He collected the seeds produced as a result of this cross and grew them to generate plants of the first hybrid generation which is called the first filial progeny or F₁: Mendel then self pollinated the tall F₁ plants and he obtained F₂ generation.
(i) In garden pea, round shape of seeds is dominant over wrinkled shape. A pea plant heterozygous for round shape of seed is selfed and 1600 seeds produced during the cross are subsequently germinated. How many seedlings would have non-parental phenotype?

(a) 1600 (b) 1200

(c) 400 (d) 800

(ii) If 'A' represents the dominant gene and 'a' represents its recessive allele, which of the following would be the most likely result in the first generation offspring when Aa is crossed with aa ?
(a) All will exhibit dominant phenotype.
(b) All will exhibit recessive phenotype.
(c) Dominant and recessive phenotypes will be 50% each.
(d) Dominant phenotype will be 75%.
(iii) Which of the following crosses will give tall and dwarf pea plants in same proportions?

A) B)

c) D)

(iv) What result Mendel would have got, if he self pollinated a homozygous tall F₂ plant?
(a) TT and Tt
(b) All Tt
(c) All TT
(d) All tt
(v) In plant, tall phenotype is dominant over dwarf phenotype, and the alleles are designated as T and t, respectively. Upon crossing one tall and one dwarf plant, total 250 plants were obtained, out of which 124 displayed tall phenotype and rest were dwarf. Thus, the genotype of the parent plants were
(a) TT x TT
(b) TT x tt
(c) Tt x Tt
d) Tt x tt.

4)

The cross that include the inheritance of two pairs of contrasting characters simultaneously is referred as dihybrid cross. Mendel chose pure breeding plants for yellow and green seeds and round and wrinkled shape of seeds. He cross pollinated the plant having yellow round seeds with plant having green wrinkled seeds. All the plants produced in F₁ generation were having, yellow round seeds. The plants raised from these seeds were self pollinated, that resulted in production of plants having four phenotypically different types of seeds.
(i) When a cross is made between a yellow round seeded plant (YyRr) and a yellow wrinkled seeded plant (Yyrr), what is true regarding the proportions of phenotypes of the offsprings in F₁ generation?

	Proportion of yellow wrinkled seeds	Proportion of green wrinkled seeds
(a)	3/8	1/8
(b)	2/8	1/8
(c)	1/8	3/8
(d)	2/8	2/8

(ii) How many types of gametes can be produced by YYrr?

(a) 1	(b) 2
(c) 3	(d) 4

(iii) In Mendelian dihybrid cross, when heterozygous tall plant with green seeds are self crossed the progenies are

(a) TtYy, TtYY, TTYy	(b) Ttyy, TTyy, ttyy
(c) ttYy, ttyy	(d) Ttyy, TTyy

(iv) When round yellow seeded heterozygous pea plants are self fertilised, the frequency of occurrence of RrYY genotype among the offsprings is

(a) 9/16	(b) 3/16
(c) 2/16	(d) 1/16.

(v) The percentage of yr gamete produced by YyRr parent will be

(a) 25%	(b) 50%
(c) 75%	(d) 12.5%.

5)
In human, the allele for brown eyes (B) is dominant over that for blue eyes (b). A brown eyed woman marries a blue eyed man, and they have six children. Four of the children are brown eyed and two of them are blue eyed.
(i) What is the genotype of blue eyed offspring?

(a) BB (b) Bb

(c) bb (d) Cannot be determined

(ii) What is the woman's genotype?

(a) BB (b) Bb

(c) bb (d) Cannot be determined

(iii) The ovum, produced by the mother carries the gene regarding eye colour is

(a) BB (b) Bb

(c) B or b (d) B only.

(iv) The ratio of brown eyed children to blue eyed children in this family is 2 : 1, which deviates from typical phenotypic ratios for monohybrid inheritance. What might be the reason?
(a) Gametes carrying the brown eyed allele are more viable then those with the blue eyed allele.
(b) A different pattern of inheritance other than monohybrid inheritance is involved.
(c) Not all of their babies survived childbirth, thus causing a distortion in the actual ratio.
(d) The actual ratio differs from the expected ratio because the sample size is too small.
(v) What is the gene carried by of the man's sperm regarding the eye colour?

(a) BB (b) Bb

(c) b only (d) b or B.

CBSE 10th Standard Science Subject Heredity and Evolution Chapter Case Study Questions 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)
Purebred pea plant with smooth seeds (dominated characteristic) were crossed with purebred pea plant with wrinkled seeds (recessive characteristic). The F₁ generation was self pollinated to give rise to the F₂generation.
(i) What is the expected observation of the F₁ generation of plants?
(a) 1/2 of them have smooth seeds and 1/2 of the have wrinkled seeds.
(b) 1/4 of them have wrinkled seeds and 3/4 of them have smooth seeds.
(c) 3/4 of them have wrinkled seeds and 1/4 of them have smooth seeds.
(d) All of them have smooth seeds.
(ii) What is the expected observation of the F₂generation of plants?
(a) 1/2 of them have smooth seeds and 1/2 of them have wrinkled seeds.
(b) 1/4 of them have wrinkled seeds and 3/4 of them have smooth seeds.
(c) 3/4 of them have wrinkled seeds and 1/4 of them have smooth seeds.
(d) All of them have smooth seeds.
(iii) If a genotype consists of different types of alleles, it is called

(a) homozygous (b) heterozygous

(c) monoallelic (d) uniallelic

(iv) The alternative form of gene is called

(a) dominant character (b) recessive character

(c) alternative genes (d) allele.

(v) Which of the following will be the genotypic ratio of given F₂ generation?

(a) 1: 3 (b) 3: 1

(c) 1: 2 : 1 (d) 1: 1 : 1
2)
In fruittlies, the gene for wing shape has two alleles, an unusual allele for curled wings (c) and the normal allele for straight wings (C). The given phenotypes are observed for each genotype.

Genotype Phenotype

CC Normal, straight wings

Cc Wings curled up at the ends, has difficulty flying

cc Unable to hatch from egg

(i) Which of the following crosses would produce live offspring from 50% of the eggs?

(a) CC x Cc (b) CC x CC

(c) CC x cc (d) Cc x cc

(i) (d)
(ii) (a)
(iii) (a): 25% of the total number of eggs will not
hatch (genotype cc). 50% of the offspring will be curlywinged
(Cc) and 25% of the offspring are straightwinged
(CC).
(iv) (c)
(v) (b)

(ii) Which of the following crosses would be able to produce offspring that would fly normally from 50% of the egg?

(a) CC x Cc (b) Cc x Cc

(c) CC x cc (d) Cc x cc

(iii) Two curly winged flies are crossed, and they produce 150 eggs. What is the proportion of straight-winged flies expected among the live offspring?

(a) 25% (b) 33%

(c) 50% (d) 75%

(iv) Normal straight winged flies are self crossed and they produce 120 eggs. What is the proportion of curly winged flies expected among the live offspring?

(a) 25% (b) 75%

(c) 0% (d) 100%

(v) Which of the following crosses would be able to produce offspring that has curled wings only?

(a) CC x Cc (b) CC x cc

(c) Cc x Cc (d) Cc x cc
3)
Refer to the schematic representation of the albinism that is an inherited condition caused by recessive allele (a). 'A' is the dominant allele for the normal condition. The inheritance of certain genetic traits for two or more generations is represented in a pedigree or family tree. Study the given pedigree chart and answer the following questions.

(i) Which of the following could be the genotypes of X and Y?

X Y

(a) AA AA

(b) AA Aa

(c) Aa Aa

(d) aa aa

(ii) Which of the following could be the genotype of generation - 1 male and female?

Male Female

(a) AA aa

(b) aa AA

(c) Aa aa

(d) AA AA

(iii) If X married an albino female, then what is the probability that their children would be albino?

(a) 0 (b) 0.125

(c) 0.25 (d) 0.5

(iv) If Y married a normal homozygous male, then what is the probability that their children would be albino?

(a) 0 (b) 0.125

(c) 0.25 (d) 0.5

(v) Which of the following could be the genotype of offsprings produced by cross of X and Y?

(a) AA, Aa, aa (b) aa, aa

(c) Aa, Aa (d) AA, AA

4)

Refer to the given table regarding results of F2 generation of Mendelian cross.

Plants with round and yellow coloured seeds (P)	315
Plants with round and green coloured seeds (Q)	108
Plants with wrinkled and yellow coloured seeds (R)	101
Plants with wrinkled and green coloured seeds (S)	32

(i) Which of the following would be the phenotype of F1 generation regarding given data of F₂ generation?
(a) Plants with round and yellow coloured seeds
(b) Plants with round and green coloured seeds
(c) Plants with wrinkled and yellow coloured seeds
(d) Plants with wrinkled and green coloured seeds.
(ii) Which of the following would be the genotype of parental generation regarding given result of F₂ generation?

(a) YYRR and yyrr	(b) YYRR and YYRR
(c) YYRR and YyRr	(d) YyRr and YyRr

(iii) If plant with wrinkled and green coloured seeds (S) is crossed with plant having wrinkled and yellow coloured seeds (R), what will be the probable phenotype of offsprings?
(a) All plants with wrinkled and yellow coloured seeds
(b) 50% plants with wrinkled and yellow coloured seeds and 50% plants with wrinkled and green coloured seeds
(c) All plants with wrinkled and green coloured seeds
(d) Both (a) and (b).
(iv) Which of the following will result when plant YyRr is self-pollinated?
(a) 9: 3 : 3 : 1 ratio of phenotypes only
(b) 9: 3 : 3 : 1 ratio of genotypes only
(c) 1-: 1 : 1 : 1 ratio of phenotypes only
(d) 1: 1 : 1 : 1 ratio of phenotypes and genotypes
(v) The percentage of yR gamete produced by YyRR parent will be

(a) 25%	(b) 50%
(c) 75%	(d) 12.5%

5)
Pea plants can have smooth seeds or wrinkled seeds. One of the phenotypes is completely dominant over the other. A farmer decides to pollinate one flower of a plant with smooth seeds using pollen from plant with wrinkled seeds. The resulting pea pod has all smooth seeds.
(i) Which of the following conclusions can be drawn?
1. The allele for smooth seeds is dominated over that of wrinkled seeds.
2. The plant with smooth seeds is heterozygous.
3. The plant with wrinkled seeds is homozygous.

(a) 1 only (b) 1 and 2 only

(c) 1 and 3 only (d) 1, 2 and 3

(ii) Which of the following crosses will give smooth and wrinkled seeds in same proportion?

(a) RR x rr (b) Rr x rr

(c) RR x Rr (d) rr x rr

(iii) Which of the following cross can be used to determine the genotype of a plant with dominant phenotype?

(a) RR x RR (b) Rr x Rr

(c) Rr x RR (d) RR x rr

(iv) On crossing of two heterozygous smooth seeded plants (Rr), a total of 1000 plants were obtained in F₁ generation. What will be the respective number of smooth and wrinkled seeds obtained in F₁ generation?

(a) 750,250 (b) 500,500

(c) 800,200 (d) 950,50

(v) The characters which appear in the first filial generation are called

(a) recessive characters (b) dominant characters

(c) lethal characters (d) non-mendelian characters

CBSE 10th Standard Science Subject How do Organisms Reproduce Chapter Case Study Questions With Solution 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

There are two organisms X and Y that produce new offspring from single parent only.Organisms X when reaches its maximum growth, divides its body into two new organisms.
The parent organism does not exist any more and two new daughter organisms grow fully and divide again. Organism Y form a small outgrowth on its body called bud which detaches and develops into new organism .
Read the above paragraph and answer the questions that follow.
(I) Select the option that correctly identifies organisms X and Y.

X	Y
(a) Amoeba	Yeast
(b) Paramecium	Hydra
(c) Leishmania	Sycon
(d) All of these

(ii) Select the correct statement.
(a) Organism X reproduces asexually whereas organism Y reproduces sexually
(b) Organism X must be multicellular whereas organism Y should be unicellular
(c) Both organisms X and Y reproduce asexually
(d) Both organisms X and Yare always multicellular organisms
(iii) Identify the mode of reproduction in organisms X and Y.

(a) X - Multiple fission Y - Binary fission	(b) X - Binary fission Y - Budding
(c) X - Regeneration Y - Fragmentation	(d) X - Fragmentation Y - Multiple fission

(iv) Which of the following is incorrect?
(a) Plasmodium reproduces by the same method as is adopted by organism X.
(b) Organism X could be any multicellular plant like Riccia, Sphagnum, etc.
(c) If organism Y is Hydra, then it may also reproduce through regeneration.
(d) Both (a) and (b)
(v) Which organism reproduces by the method shown in the given figure?

(a) Planaria	(b) Amoeba
(c) Euglena	(d) Paramecium

2)
Spore formation, method of asexual reproduction is used by unicellular as well as multicellular organisms.Spores are microscopic units which could be air borne or are present in soil, etc.
(i) A slice of bread kept in open for sometime shows growing white cottony mass which later turns black. This happens because
(a) bacterial spores present in air germinate on the surface of bread slice
(b) fungal spores present in air germinate on the surface of bread slice
(c) protozoan microbes start feeding on bread slice
(d) none ef these.
(ii) Spore formation can be seen in

(a) Mucor (b) sweat potato

(c) Spirogyra (d) all of these

(iii) Bulb like structure at top of erect hyphae where spores are produced is

(a) sporangiophore (b) apophysis

(c) columella (d) sporangia.

(iv) Select the incorrect statement.
(a) Spores can be produced endogenously or exogenously in an organism.
(b) Spores can be air borne or soil borne.
(c) Bacteria produce only exospores.
(d) Rhizopus bears spores in special structures called sporangium.
(v) Observe the given figure showing spores formation in Rhizopus and select the option which is correctly labelled.

(a) P-Stolon, S-Columella, T-Sporangiophore
(b) Q-Stolon, P-Hypha, S-Sporangium
(c) R-Sporangium, S-Apophysis, T-Sporangiophore
(d) Q-Stolon, R-Sporangium, S-Colume!la
3)
Radhika collected some pond water which was dark green in colour in a test tube. She took out green coloured mass from it and separated its filaments by using needles. She broke some filaments into small fragments and put them in a Petri dish containing clean water. She observed that after few days the small fragments gave rise to complete filaments.
(i) What do you think the mass of green filament was?
(a) It was a mass of Spirogyra filament
(b) It was a colony of Volvox algae
(c) It was kelp, i.e., large brown algae
(d) It was a mass of fungal filaments or hyphae.
(ii) The small fragment gave rise to new filament. What does it indicate?
(a) Spirogyra reproduces asexually through fragmentation
(b) Spirogyra reproduces asexually through vegetative propagation
(c) Spirogyra reproduces asexually through budding
(d) Spirogyra reproduces asexually through fission
(iii) Organism which reproduces in similar way as Spirogyra is

(a) yeast (b) sea anemone

(c) Entamoeba (d) all of these.

(iv) Select the correct statement.
(a) Only multicellular organisms can undergo fragmentation
(b) Both unicellular and multicellular organisms can undergo fragmentation
(c) Fragmentation is sexual mode of reproduction
(d) Fragmentation is found only in algae.
(v) Which among the given organisms do not reproduce by fragmentation?

(a) Riccia (b) Selaginella

(c) Aurelia (d) Marchantia
4)
Preeti is very fond of gardening. She has different flowering plants in her garden. One day few naughty children entered her garden and plucked many leaves of Bryophyllum plant and threw them here and there in the garden. After few days, Preeti observed that new Bryophyllum plants were coming out from the leaves which fell on the ground.
(i) What does the incidence cited in the paragraph indicate?
(a) Bryophyllum leaves have special buds that germinate to give rise to new plant
(b) Bryophyllum can propagate vegetatively through leaves
(c) Bryophyllum is a flowering plant that reproduces only asexually
(d) Both (a) and (b)
(ii) Which of the following plants can propagate vegetatively through leaves like Bryophyllum?

(a) Guava (b) Begonia

(c) Ginger (d) Mint

(iii) Do you think any other vegetative part of Bryophyllum can help in propagation? If yes, then which part?

(a) Roots (b) Stems

(c) Flowers (d) Fruits

(iv) Which of the following plants is artificially propagated (vegetatively) by stem cuttings in horticultural practices?

(a) Potato (b) Snake plant

(c) Rose (d) Water hyacinth

(v) In which of the following pairs both the plants can be vegetatively propagated by leaf pieces?

(a) Adiantum and Kalanchoe (b) Chrysanthemum and Agave

(c) Agave and Dioscorea (d) Bryophyllum and Asparagus

5)

Horticultural methods of vegetative propagation multiply desired varieties of plants quickly from parts of their somatic body. A horticulturist used stem cutting of plant X to propagate it in a short span of time. For plant Y, he pulled a branch of towards ground and covered it with soil leaving the tip of branch exposed. He later on cut the branch from parent plant. The former developed into new plant. He propagated plant Z through underground stems called tubers. Identify the propagation methods used by horticulturist and answer the following questions.
(i) What could be plants X, Y and Z?

	X	Y	Z
(a)	Bougainvillea	Jasmine	Potato
(b)	Sugarcane	Ginger	Rose
(c)	Begonia	Banana	Chrysanthemum
(d)	Guava	Onion	Cactus

(ii) Select the propagation methods in plants X, Y and Z.
(a) X - root tubers, Y - stem cutting, Z - stem tubers
(b) X - stem cutting, Y - layering, Z - underground stem
(c) X -Iayering, Y - underground stem, Z - underground roots
(d) X - grafting, Y - layering, Z - root tubers
(iii) Select the correct statement for plant Z if it is potato.
(a) Each tuber has many buds called ears
(b) It is necessary to plant the whole potato tuber in the soil to produce new potato plants
(c) Vegetative propagation of potato plants by tubers is much faster than production of potatoes by seeds
(d) All of these.
(iv) Select the plant which propagates by the same method adopted by gardener for plant Y, but naturally it propagates by stolons

(a) Strawberry	(b) Adiantum
(c) Tulsi	(d) Both (a) and (b)

(v) Identify the given vegetative propagule.

(a) Bulb	(b) Runner
(c) Rhizome	(d) Bulbil

CBSE 10th Standard Science Subject How do Organisms Reproduce Chapter Case Study Questions 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)
A newly married couple does not want have children for few years. They consulted a doctor who advised them barrier method and chemical method of birth control. Yet another couple who already have two children and are middle aged also consulted doctor for some permanent solution to avoid unwanted pregnancy. Doctor advised them surgical method of birth control.
(i) What are the barrier methods of birth control?

(a) Condom (b) Diaphragm

(c) Oral pills (d) Both (a) and (b)

(ii) How physical barrier prevent pregnancy?
(a) They kill the sperms
(b) They kill the ovum
(c) They prevent sperms from meeting the ovum
(d) They prevent intercourse
(iii) How chemical methods prevent pregnancy?
(a) Vaginal pills contain chemical called spermicides which kill the sperms
(b) Oral pills prevent ovulation so there will be no fertilisation
(c) Oral pills stop menstruation in females
(d) Both (a) and (b)
(iv) Select the correct statement regarding surgical method of birth control.
(a) It involves termination of pregnancies in women particularly after eight weeks of conception
(b) Small portion of sperm duct or vas deferences in males is removed by surgical operation and both cut ends are ligated properly
(c) Small portion of oviducts in females is removed by surgical operation and cut ends are ligated
(d) Both (b) and (c)
(v) Select the correct statement regarding birth control methods.
(a) Barrier method of birth control also protects the couple from sexually transmitted diseases
(b) Some women experience unpleasant side effects on taking oral pills because of change in hormonal balance in body
(c) Surgical method in males is called vasectomy and in females is called tubectomy
(d) All of these
2)
A married woman used a device X made of common metal for preventing pregnancy. This device was put into her uterus by some trained medical professional. Unfortunately she got pregnant after two months of insertion of device. She was in shock to learn that her birth control device has failed.
(i) What is the name of birth control device used by the woman?

(a) Foam tablets (b) Copper T

(c) Diaphragm (d) Both (a) and (b)

(ii) Which metal is commonly used for making device X?

(a) Iron (b) Copper

(c) Silver (d) Gold

(iii) How does device X prevent pregnancy?
(a) It prevents ovulation
(b) It prevents copulation
(c) It suppresses fertilising capacity of sperm
(d) None of these
(iv) Why do you think the woman got pregnant even after using device X?
(a) Device X might have got expelled without the knowledge of woman
(b) Device X might be defective and was not working from the beginning
(c) Device X could have been destroyed by the uterine fluid
(d) None of these
(v) Select the correct statement regarding device X.
(a) Device X is very effective in preventing sexually transmitted diseases
(b) Device X can be inserted in uterus by woman herself
(c) Device X prevents menstrual cycle in women
(d) Device X can cause heavy painful and longer duration periods or menstruation

3)

X, Y and Z are sexually reproducing organisms. Fertilisation occurs either in external medium (water) or inside the body of organism. Thus two types of gametic fusion are external fertlisation and internal fertilisation. X undergoes external fertilisation whereas Y and Z undergo internal fertilisation. X and Y both release their eggs outside their body.
(i) Select the option that correctly identifies organisms X, Y and Z.

X	Y	Z
(a) Fish	Frog	Goat
(b) Frog	Pigeon	Elephant
(c) Toad	Gorilla	Sparrow
(d) Kiwi	Fish	Duck-billed platypus

(ii) Select the correct statement regarding organisms X and Y.
(a) Y produces large number of eggs where X produces single egg at a time.
(b) Fertilisation in case of X occurs in water but fertilisation occurs inside the body of Y.
(c) X could be a reptile whereas Y could be fish or amphibian.
(d) Eggs of X are covered by hard calcareous shell whereas eggs ofY are covered in jelly.
(iii) Select the incorrect statement regarding organisms Y and Z.
(a) Y is oviparous whereas Z is viviparous.
(b) Zygote develops to complete baby in the bodies of organism Y and Z.
(c) Y could be a bird or reptile whereas Z could be a mammal.
(d) Both Y and Z copulate with their female counterparts to transfer sperms in their bodies.
(iv) Select the correct match.
(a) Eggs with calcareous shells - Parrot, King Cobra, Salmon
(b) Eggs with jelly covering - Toad, Eagle, Lizard
(c) Eggs without shell - Cat, Dog, Human
(d) Eggs produced in large numbers at a time - Rohu, Human, Python
(v) Why are eggs of animal X covered in jelly?
(a) To keep the eggs moist and offer some protection from predators
(b) To prevent the egg from breaking
(c) To prevent fertilisation of eggs
(d) All of these

4)

Menstrual cycle is the cycle of events taking place in female reproductive organs, under the control of sex hormones, in every 28 days. At an interval of 28 days, a single egg is released from either of two ovaries. Regular menstrual cycle stopped abruptly in a married women. She got herself tested and was happy to discover that she is pregnant with her first baby.
(i) Why menstruation stops in a pregnant female?
(a) The egg gets fertilised so need not to be expelled out of body
(b) Ovulation stops during pregnancy and so do menstruation
(c) Thick uterine lining is needed for proper development of embryo, so that it is retained
(d) All of these
(ii) Select the correct sequence of acts that leads to pregnancy in a female.
A. Fertilisation of egg
B. Ovulation
C. Formation of zygote
D. Implantation

(a) D \(\Rightarrow\)C \(\Rightarrow\)B \(\Rightarrow\)A	(b) B\(\Rightarrow\) A\(\Rightarrow\)C\(\Rightarrow\)D
(c) A \(\Rightarrow\) B\(\Rightarrow\) C\(\Rightarrow\) D	(d) D\(\Rightarrow\) C\(\Rightarrow\) A \(\Rightarrow\)B

(iii) How is a zygote different from embryo?
(a) Zygote is formed by repeated division of embryo
(b) Zygote is formed by fusion of sperm and egg whereas embryo is formed by fusion of zygote with other zygote
(c) Zygote is single celled but embryo is multicellular
(d) Zygote is formed by fertilisation but embryo is formed without fertilisation
(iv) What change takes place in the uterus of a pregnant female?
(a) Uterine lining becomes thick and vascular
(b) Placenta develops which links the embryo to mother through umbilical cord
(c) Uterus lining containing lots of blood capillaries breaks down
(d) Both (a) and (b)
(v) Select the correct statement.
(a) The average duration of human pregnancy is about nine months
(b) The time period from fertilisation up to the birth of baby is called gestation
(c) If doctor finds any anomaly in the developing fetus then he may terminate pregnancy at an early stage, known as abortion
(d) All of these

5)

X, Y and Z are three sexually transmitted diseases (STDs). X and Z are caused by bacteria whereas Y is caused by virus P. Virus P lowers the immunity of a person and leads to an incurable disease. X starts as painless sores on genitals rectum or mouth. Z causes painful urination and abnormal discharge from genitals.
(i) Select the option that correctly identifies disease X, Y and Z?

X	Y	Z
(a) AIDS	Syphilis	Gonorrhoea
(b) Syphilis	AIDS	Gonorrhoea
(c) Gonorrhoea	Syphilis	AIDS
(d) Syphilis	Gonorrhoea	AIDS

(ii) Identify virus P from the given paragraph.
(a) Human papilloma virus
(b) Human adenovirus
(c) Human immunodeficiency virus
(d) Human cytomegalovirus
(iii) What are the symptoms of disease Y?
(a) Weight loss
(b) Fever or night sweats
(c) Fatigue and weakness infections
(d) All of these
(iv) Select the incorrect statement regarding diseases X and Y.
(a) Both X and Y can spread from infected mother to unborn baby during pregnancy
(b) Both X and Y can spread from infected partner to healthy partner by unprotected sex
(c) Y can also spread through use of contaminated needles and blood transfusion
(d) None of these.
(v) How can disease Y be prevented?
(a) By following polygamy and having protected sex
(b) Use of sterilised needles for injecting medicines, blood tests, etc
(c) Collecting blood from unknown donors without background check by blood bank professionals
(d) All of these.

CBSE 10th Standard Science Subject Life Processes Chapter Case Study Questions With Solution 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

In fermentation, the incomplete oxidation of glucose achieved under anaerobic conditions by sets of reactions where pyruvic acid is converted to CO₂and ethanol. The enzymes, pyruvic acid decarboxylase and alcohol dehydrogenase catalyse these reactions.
(i) The given experimental set-up demonstrates

(a) photosynthesis	(b) aerobic respiration
(c) anaerobic respiration	(d) ascent of sap

(ii) Fermentation is represented by the equation
\(\text { (a) } \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+6 \mathrm{O}_{2} \rightarrow 6 \mathrm{CO}_{2}+6 \mathrm{H}_{2} \mathrm{O}+686 \mathrm{kcal}\)
\(\text { (b) } \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} \rightarrow 2 \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{OH}+2 \mathrm{CO}_{2}+59 \mathrm{kcal}\)
\(\text { (c) } 6 \mathrm{CO}_{2}+12 \mathrm{H}_{2} \mathrm{O} \frac{\text { Light }}{\text { Chlorophyll }}>\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+6 \mathrm{H}_{2} \mathrm{O}+6 \mathrm{O}_{2}\)
\(\text { (d) } 6 \mathrm{CO}_{2}+6 \mathrm{H}_{2} \mathrm{O} \rightarrow \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6}+6 \mathrm{O}_{2} \text { . }\)
(iii) A test tube containing molasses solution and yeast is kept in a warm place overnight. The gas collected from this mixture

(a) extinguishes the flame	(b) bursts into flame when ignited
(c) turns lime water milky	(d) both (a) and (c)

(iv) Ethyl alcohol fermentation occurs in

(a) Lactobacillus

(b) muscles of humans

(c) Yeast

(d) all of these

(v) Though vertebrates are aerobes, but their (i) show anaerobic respiration during (ii) During this (iii) of skeletal muscle fibres is broken down-to release lactic acid and energy. Lactic acid, if accumulates causes muscle fatigue.
Fill up the blanks in the above paragraph and select the correct option

(i)	(ii)	(iii)
(a) skeletal muscles	heavy exercise	glucose
(d) skeletal muscles	mild exercise	glycogen
(c) skeletal muscles	heavy exercise	glycogen
(d) cardiac muscles	heavy exercise	glycogen

2)
Double circulation is a type of circulating system in which the blood passes through the heart twice before completing a full circuit of the body. Blood is pumped from the heart to the lungs and returns to the heart before being distributed to other organs and tissues of the body.
(i) The figure shows blood circulation in humans with labels A to D. Select the option which gives correct identification of label and functions of the part.

(a) B - Capillary- Thin without muscle layer and wall two cell layers thick
(b) C - Vein-Thin walled and blood flows in jerks/spurts
(c) D - Pulmonary vein-Takes oxygenated blood to heart, PO₂ = 95 mm Hg
(d) A - Artery-Thick walled and blood flows evenly
(ii) Incomplete double circulation is seen in

(a) mammals (b) pisces (c) aves (d) amphibians.

(iii) Which of the following animals shows double circulatory pathway?

(a) Snake (b) Frog (c) Eel (d) Whale

(iv) The given figure is of circulatory system. Identify the labelled parts (A-D) from the list (I-VII).

(I) Pulmonary circulation (II) Systemic circulation (III) Superior vena cava (IV) Inferior vena cava
(V) Aorta (VI) Veins and venules (VII)Arterioles and capillaries

(a) A-(V), B-(lII), C-(I), D-(VII) (b) A-(VII), B-(IV), C-(I), D-(VI)

(c) A-(V), B-(III), C-(lI), D-(VII) (d) A-(VII), B-(V), C- (I), D-(VI)

(v) Select the option which properly represents pulmonary circulation in humans.
\(\text { (a) Left auricle } \frac{\text { Deoxygenated }}{\text { blood }}{\longrightarrow} \text { Lungs } \frac{\text { Oxygenated }}{\text { blood }} \text { Right ventricle }\)
\(\text { (b) Left auricle } \frac{\text { Oxygenated }}{\text { blood }}{\longrightarrow} \text { Lungs } \frac{\text { Deoxygenated }}{\text { blood }}{\longrightarrow} \text { Right ventricle }\)
\(\text { (c) Right ventricle } \frac{\text { Deoxygenated }}{\text { blood }}{\longrightarrow} \text { Lungs } \frac{\text { Oxygenated }}{\text { blood }} \rightarrow \text { Left auricle }\)
\(\text { (d) Right ventricle } \frac{\text { Oxygenated }}{\text { blood }}>\text { Lungs } \frac{\text { Deoxygenated }}{\text { blood }} \gg \text { Left auricle }\)
3)
Transpiration is the evaporative loss of water by plants. It occurs mainly through the stoma in the leaves. Besides the loss of water vapour in transpiration, exchange of oxygen and carbon dioxide in the leaf also occurs through pores called stomata. Normally stomata remain open in the day time and close during the night
(i) Which of the following will not directly affect transpiration?

(a) Temperature (b) Light

(c) Wind speed (d) Chlorophyll content of leaves

(ii) Water vapour comes out from the plant leaf through the stomatal opening. Through the same stomatal opening, carbon dioxide diffuses into the plant during photosynthesis. Reason out the above statements . using one of following options.
(a) The above processes happen only during night time.
(b) One process occurs during day time and the other at night.
(c) Both processes cannot happen Simultaneously.
(d) Both processes can happen together at day time.
(iii) Which of the following statements is not true for stomatal apparatus?
(a) Guard cells invariably possess chloroplasts and mitochondria.
(b) Guard cells are always surrounded by subsidiary cells.
(c) Stomata are involved in gaseous exchange.
(d) Inner wall of guard cells are thick.
(iv) Which of the following is not a purpose of transpiration?
(a) Helps in absorption and transport in plants
(b) Prevents loss of water
(c) Maintains shape and structure of plants by keeping the cells turgid
(d) Supplies water for photosynthesis
(v) Refer to the given graphs regarding factors affecting transpiration rate and select the correct option.

(a) P-Atmospheric temperature; Q-Atmospheric pressure
(b) P-Relative humidity; Q-Atmospheric temperature
(c) P-Air movement; Q-Light
(d) P-Atmospheric pressure; Q-Relative humidity

4)

We need energy to perform various activities. This energy is derived from the catabolism of various components of food, e.g., proteins, carbohydrates, fats, etc. Oxygen is required for catabolic processes and carbon dioxide is released in the process. So, the body requires a continuous exchange of gases, oxygen from the atmosphere is taken inside and carbon dioxide produced is given out. In human beings, respiratory pigment called haemoglobin present in RBCs has very high affinity for oxygen. In tissues, exchange of gases occurs between oxygenated blood and tissue cells.
(i) People living at sea level have around 5 million RBCs per cubic millimetre of their blood whereas those living at an altitude of 5400 metres have around 8 million. This is because at high altitude
(a) people eat more nutritive food, therefore more RBCs are formed
(b) people get pollution-free air to breathe and more oxygen is available
(c) atmospheric 02 levelisless and hence more RBCs are needed to absorb the required amount of 02 to survive
(d) there is more UV radiation which enhances RBC production.
(ii) The given graph illustrates the changes in lung volume during the process of breathing .

The change from II to III indicates the

(a) movement of diaphragm away from the lungs	(b) expansion of the thoracic cavity
(c) movement of air out of the lungs	(d) expansion of ribs.

(iii) Which one of the following is a possibility for most of us in regard to breathing, by making a conscious effort?
(a) One can breathe out air totally without oxygen.
(b) One can breathe out air through Eustachian tube by closing both nose and mouth.
(c) One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all.
(d) The lungs can be made fully empty by forcefully breathing out all air from them.
(iv) Refer to the given figure and answer the following question .

Which of these parts
(I) are the actual sites of respiratory gas exchange?
(II) is the common passage for air and food?
(III) is provided with incomplete cartilaginous rings?
(IV) relaxes and gets back to its original shape during expiration?
(v) moves upwards and outwards during inspiration?

(a) (I) - s, (II) - p, (III) - q, (IV) - r, (V) - t	(c) (I) - t, (II) - q, (III) - r, (IV) - s, (V) - P
(b) (I) - r, (II) - p, (III) - q, (IV) - s, (V) - t	(d) (I) - p, (II) - q, (III) - r, (IV) - s, (V) - t

(v) Which of the following sequences is correct to initiate inspiration?
(I) The contraction of intercostal muscles raises the ribs and sternum
(II) Volume of thorax increases
(III) Intrathoracic pressure of the lungs decreases
(IV) Diaphragm contraction
(v) Air rushes into lungs

(a) (I), (II), (IV), (V), (III)	(b) (I), (II), (III), (IV), (V)
(c) (I), (IV), (II), (III), (V)	(d) (V), (I), (II), (III), (IV)

5)

The green plants make their food, through photosynthesis and are therefore called autotrophs. All other organisms depend upon green plants for food and are referred to as heterotrophs. Green plants carry out photosynthesis by using light energy of sun. The first phase of reactions are directly light driven therefore called light reactions. The second phase of reactions are not directly light driven but are dependent on the products of light reactions and are called dark reactions.
(i) Which of the following is produced during the light phase of photosynthesis?

(a) ATP

(b) NADPH

(c) Carbohydrate

(d) Both (a) and (b)

(ii) In the overall process of photosynthesis, the number of sugar molecules produced is

(a) 12

(b) 6

(c) 4

(d) l

(iii) A plant is provided with ideal conditions for photosynthesis and supplied with isotope ¹⁴CO₂. When the products of the process are analysed carefully, what would be the nature of products?
(a) Both glucose and oxygen are normal.
(b) Both glucose and oxygen are labelled.
(c) Only glucose is labelled and oxygen is normal.
(d) Only oxygen is labelled and glucose is normal.
(iv) Refer to the given diagrammatic representation of an electron micrograph of a section of chloroplast and answer the question .

Select the option which correctly depicts the functions of parts X, Y and Z.

X	Y	Z
(a) Dark reaction	Light reaction	Carbohydrate synthesis
(b) Light reaction	Carbohydrate synthesis	Carbohydrate storage
(c) Light reaction	Carbohydrate storage	Carbohydrate synthesis
(d) Carbohydrate synthesis	Carbohydrate storage	Cytoplasmic inheritance

(v) Following table summarises the differences between light and dark reactions.

Light reactions	Dark reactions
(I) These are also called biosynthetic phase	These are also called photochemical phase.
(II) These reactions occur over thylakoids.	These reactions occur in stroma of chloroplasts
(III) These produce assimilatory power i.e NADPH and ATP	These consume NADPH and ATP
(IV) These are directly dependent upon light	They depend upon the products synthesised during light reactions

Which of the following is correct group of differences?

(a) (I), (II) and (III)	(b) (II), (III) and (IV)
(c) (II) and (III)	(d) (I) and (IV)

CBSE 10th Standard Science Subject Life Processes Chapter Case Study Questions 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

Digestion is a catabolic process in which complex and large components of food are broken down into their respective simpler and smaller forms with the help of various hydrolytic enzymes. In human, the process of intake of essential nutrients in the form of food takes place through an entire system known as digestive system. The digestive system in human includes alimentary canal and its associated digestive glands.
(i) Identify the cells whose secretion protects the lining of gastro-intestinal tract from various enzymes.

(a) Duodenal cells

(b) Chief cells

(c) Goblet cells

(d) Oxyntic cells

(ii) Digestion of proteins is incomplete in the absence of enterokinase, because
(a) trypsinogen is not converted into trypsin
(b) pepsinogen is not converted into pepsin
(c) prorennin is not converted into rennin
(d) chymotrypsinogen is not converted into chymotrypsin
(iii) Match the column I with column II and column III. Choose the correct option.

Column I	Column II	Column III
(Substrate)	(Enzyme)	(Product)
1. Lactose	A. Lipase	I. Galactose
2. Fatty acid	B. Trypsin	II. Maltose
3. Starch	C. Lactase	III. Glycerol
4. Proteins	D. Amylase	IV. Dipeptides

(a) 1- A-I; 2-C-II; 3-B-III; 4-D-IV	(b) I-D-I; 2-A-II; 3-B-III; 4-C-IV
(c) l-C-I; 2-A-III; 3-D-II; 4-B-IV	(d) l-C-I; 2-A-II; 3-D-III; 4-B-IV

(iv) A and B in the given graph are the action spectra of the two enzymes. The two enzymes are

(a) A: amylase	B: trypsin
(b) A: pepsin	B: trypsin
(c) A: chymotrypsin	B: rennin
(d) A: lactate dehydrogenase	B: amylase.

(v) If the inner surface of the ileum in the human small intestine was smooth, rather than being folded and subdivided into villi, which of the following statements would be true?
(a) The rate of absorption of digested food molecules would be higher, because the digested food would pass more easily through the digestive tract.
(b) Digestion would not be as effective, because there would be fewer cells secreting trypsin (a proteindigesting enzyme).
(c) Humans would have needed to evolve a much longer small intestine to absorb sufficient nutrients from their food.
(d) Humans would not be able to survive, because the digestive tract would be more susceptible to damage.

2)

Respiration is an energy releasing enzymatically controlled process which involves a stepwise oxidative breakdown of food substances inside living cells. The oxidative breakdown of respiratory substrates with the help of atmospheric oxygen is aerobic respiration. Glucose is completely broken down into CO₂ and H₂O by this process of oxidation and large amount of energy is produced.
(i) Site of Krebs' cycle is

(a) peroxisome

(b) cytoplasm

(c) mitochondria

(d) none of these.

(ii) The pathway of respiration common in all living organisms is X ;it occurs in the Y and the products formed are two molecules of Z.
Identify X, Y and Z in the above paragraph and select the correct answer.

X	Y	Z
(a) glycolysis	mitochondrion	pyruvic acid
(b) glycolysis	cytoplasm	pyruvic acid
(c) Krebs' cycle	cytoplasm	acetyl CoA
(d) Krebs' cycle	mitochondrion	acetyl CoA

(iii) Number of oxygen molecules utilised in glycolysis is ____________.

(a) 0

(b) 2

(c) 4

(d) 6

(iv) How many ATP molecules could maximally be generated from one molecule of glucose, if the complete oxidation of one molecule of glucose to CO₂ and H₂O yields 686 kcal and the useful chemical energy available in the high energy phosphate bond of one molecule of ATP is 12 kcal?

(a) 1

(b) 2

(c) 30

(d) 57

(v) The end product of aerobic respiration is

(a) NADH

(b) oxygen

(c) ADP

(d) CO₂+ ATP + H₂O

3)
Heterotrophic nutrition is a mode of nutrition in which organisms obtain readymade organic food from outside sources. The organisms that depend upon outside sources for obtaining organic nutrients are called heterotrophs. Heterotrophic nutrition is of three types: saprophytic, parasitic and holozoic nutrition.
(i) In which of the following groups of organisms food material is broken outside the body and absorbed?

(a) Mushroom, green plants, Amoeba (b) Yeast, mushroom, bread mould

(c) Paramecium, Amoeba, Cuscuta (d) Cuscuta, lice, tapeworm

(ii) Which of the following is a parasite?

(a) Yeast (b) Taenia (c) Amoeba (d) Earthworm

(iii) Which of the following is an example of saprotroph?

(a) Grass (b) Mushroom (c) Amoeba (d) Paramecium

(iv) Heterotrophic nutrition involves
(a) production of simple sugar from inorganic compounds
(b) utilisation of chemical energy to prepare food
(c) utilisation of energy obtained by plants
(d) all of these.

(v) In Paramecium, food enters the body through

(a) mouth (b) pseudopodia (c) cilia (d) cytostome
4)
The small intestine is a tubular structure within the abdominal cavity that carries the food in continuation with the stomach up to the colon from where the large intestine carries it to the rectum and out of the body. The main function of this organ is to aid in digestion. All nutrients are usually absorbed into blood across the mucosa of the small intestine. In addition, the small intestine absorbs water and electrolytes, thus playing critical role in maintenance of body water and acid-base balance.
(i) Which of the following is incorrect regarding intestinal villi?
(a) They possess microvilli.
(b) They increase the surface area.
(c) They are supplied with capillaries and the lacteal vessels.
(d) They only participate in digestion of fats
(ii) Which enzymes are likely to act on the baked potatoes eaten by a man, starting from the mouth as they move down the alimentary canal?
(a) Pancreatic amylase \(\rightarrow\) Salivary amylase \(\rightarrow\) Lipases
(b) Disaccharidase like maltase \(\rightarrow\) Lipases \(\rightarrow\) Nucleases
(c) Salivary amylase \(\rightarrow\) Pancreatic amylase \(\rightarrow\) Disaccharidases
(d) Salivary maltase \(\rightarrow\) Carboxypeptidase \(\rightarrow\) Trypsinogen
(iii) After surgical removal of an infected gall bladder, a person must be especially careful to restrict dietary intake of
(a) starch (b) protein (c) sugar (d) fat.
(iv) The given flow chart shows the fate of carbohydrates during digestion in the human alimentary canal. Identify the enzymes acting at stages indicated as A, B, C and D and select the correct option.

(a) A - Amylase, B - Maltase, C - Lactase, D - Invertase
(b) A - Amylase, B - Maltase, C - Invertase, D - Lactase
(c) A - Amylase, B - Invertase, C - Maltase, D - Lactase
(d) A - Amylase, B - Lactase, C - Maltase, D - Invertase
(v) The given diagram represents a section of small intestinal mucosa. Identify A, Band C.

(a) A-Villi, B-Lacteal, C-Capillaries (b) A-Lacteal, B-Villi, C-Capillaries

(c) A-Villi, B-Lacteal, C-Crypts (d) A-Crypts, B-Lacteal, C-Capillaries

5)

The food which is prepared by the process of photosynthesis in the leaves of a plant has to be transported to other parts like stem, roots, branches, etc. Therefore this food is transported to other parts of the plant through phloem.
(i) A few drops of sap were collected by cutting across a plant stem by a suitable method. The sap was tested chemically. Which one of the following test results indicates that it is phloem sap?

(a) Acidic	(b) Alkaline
(c) Low refractive index	(d) Absence of sugar

(ii) What is the direction of movement of sugars in phloem?

(a) Bi-directional	(b) Non-directional
(c) Upward	(d) Downward

(iii) The given diagram shows a potato plant forming new tubers. Which route would be taken by most of the food at this time?

\(\text { (a) } 1 \rightarrow 4 \rightarrow 2 \rightarrow 3\)	\(\text { (b) } 6 \rightarrow 5 \rightarrow 2 \rightarrow 3\)
\(\text { (c) } 1 \rightarrow 4 \rightarrow 5 \rightarrow 6\)	\(\text { (d) } 6 \rightarrow 5 \rightarrow 4 \rightarrow 1\)

(iv) A girdled plant (upto bast) may survive for some time but it will eventually die, because
(a) water will not move downwards
(b) water will not move upwards
(c) sugars and other organic materials will not move downwards
(d) sugars and other organic materials will not move upwards
(v) Phloem sap is mainly made of

(a) water and sucrose	(b) water and minerals
(c) oligosaccharides and hormones	(d) sucrose only

CBSE 10th Standard Science Subject Periodic Classification of Elements Chapter Case Study Questions With Solution 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)
After the discovery of large number of elements it became necessary to classify them and arrange them in a regular manner in order of their periodic properties. In 1817, Johann Wolfgang Dobereiner tried to arrange the elements with similar properties into groups. He identified some groups of three elements having similar physical and chemical properties, known as Dobereiners triads.
In 1865, John Newlands arranged all known elements in the order of increasing atomic masses and found that the properties of every eighth element are similar to the properties of the first element.
(i) If CI, Br, I is a Dobereiners triad and the atomic masses of CI and I are 35.5 and 127 respectively, then the atomic mass of Br is

(a) 162.5 (b) 91.5

(c) 81.25 (d) 45.625

(ii) Example of Dobereiner's triad is

(a) Li, AI, Ca (b) Li,Na, K

(c) Li, K, Na (d) K, AI, Ca

(iii) A and B are two elements having similar properties which obey Newlands' law of octaves. How many elements are there in between A and B?

(a) 7 (b) 8

(c) 5 (d) 6

(iv) According to the Newlands' law of octaves, the properties of magnesium are similar to those of

(a) beryllium (b) lithium

(c) sodium (d) potassium

(v) On what basis the elements are arranged in Dobereiner's triad?

(a) Atomic number (b) Atomic mass

(c) Number of neutrons (d) Number of electrons
2)
Mendeleev arranged the 63 elements known at that time in order of their ascending atomic masses and prepared a periodic table. Mendeleev's periodic table contains vertical columns called 'groups' and horizontal rows called 'periods': Elements with similar properties were placed in same groups.
The basis of Mendeleev's classification is his periodic law which states that:
(I) Atomic mass is the fundamental property of elements.
(II) The physical and chemical properties of elements are periodic function of their atomic masses.
(i) Which of the following metals is not placed in eighth group of Mendeleev's periodic table?

(a) Fe (b) Na

(c) Co (d) Ni

(ii) In Mendeleevs periodic table, silver belongs to IB group. The group to which silver belongs in the modern periodic table is

(a) first (b) eleventh

(c) tenth (d) sixteenth

(iii) In Mendeleev's periodic table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the periodic table later?

(a) Chlorine (b) Silicon

(c) Oxygen (d) Germanium

(iv) The properties of eka-aluminium predicted by Mendeleev were the same as properties of which element that was discovered later?

(a) Scandium b) Germanium

(c) Gallium (d) Aluminium

(v) Which of the following statements is not correct about Mendeleev's periodic table?
(a) In the mendeleev's periodic table, some places were left vacant for new elements which were not discovered at that time.
(b) Group VIII like groups I-VII has been divided into two sub-groups A and B.
(c) The group of an element in the periodic table represents its valency.
(d) Li and C belong to same period in Mendeleevs periodic table.
3)
In 1913, Henry Moseley showed that the atomic number of an element is the more fundamental property than its atomic mass. Accordingly, Mendeleev's periodic law was modified and atomic number was adopted as the basis of modern periodic table.
In this periodic table, the elements are arranged in increasing order of their atomic numbers.
There are 18 vertical columns in the periodic table which constitute 18 groups or families. The groups are numbered as 1, 2, 3, ... up to 18. All the members of a particular group have similar outer shell electronic configuration. There are seven horizontal rows of the periodic table which are known as periods.
(i) According to modern periodic law, the properties of elements are the periodic function of their

(a) atomic masses (b) atomic volumes

(c) atomic numbers (d) densities

(ii) All the elements in a period in the periodic table have the same

(a) atomic number (b) electronic configuration

(c) atomic weight (d) valence shell

(iii) Which of the following combinations of elements belong to the same group?

(a) N, P, As (b) Li, Be, Al

(c) Na, Mg, Al (d) O, S, Cl

(iv) The atoms of elements belonging to the same group of periodic table have same number of

(a) protons (b) electrons

(c) neutrons (d) electrons in outermost shell

(v) In the periodic table, the element with atomic number 16 will be placed in the group

(a) fourteen (b) sixteen

(c) thirteen (d) fifteen
4)
Maximum number of electrons that can be accommodated in a shell is given by the formula: 2n², where n is the number of the outermost from the nucleus.
For example,
K shell - 2 x (1)² => 2, hence, K-shell can accommodate maximum 2 electrons.
L shell - 2 x (2)² => 8, hence, L-shell can accommodate maximum 8 electrons.
In the modern periodic table, elements are placed according to their electronic configuration. The elements present in any group have the same number of valence electrons. The elements present in any period contain the same number of shells. The first period of the modern periodic table corresponds to the filling of electrons in the first energy shell, i.e., K-shell, first period has two elements. The second period of the periodic table corresponds to the filling of electrons in the second energy shell, i.e., L-shell, second period contains eight elements. The third, fourth, fifth, sixth and seventh periods have 8, 18, 18,32 and 32 elements respectively.
(i) Electronic configuration of an element 'X' is 2, 1. The number of elements present in the period to which 'X'belongs is

(a) 8 (b) 32

(c) 18 (d) 2

(ii) Among the given elements A, B, C, D and E with atomic numbers 2, 3, 7, 10 and 30 respectively, which of these belong to the same period?

(a) A,B,C (b) B,C,D

(c) A,D,E d) B,D,E

(iii) The elements A, B, C and D have atomic numbers 4, 12, 17 and 19 respectively. Which pair of elements belong to the same period?

(a) B and C (b) A and B

(c) A and D (d) C and D

(iv) Which of the following have the same number of electrons in outermost shell?
(a) Elements with atomic numbers 3, 11, 19
(b) Elements with atomic numbers 14, 15, 16
(c) Elements with atomic numbers 12, 20, 28
(d) Elements with atomic numbers 10, 18, 26
(v) Which of the following elements has two shells and both are completely filled?

(a) Helium (b) Neon

(c) Calcium (d) Fluorine
5)
All the elements on the left side and in the middle of the periodic table (except hydrogen) are metallic elements or metals. Also, majority of elements in periodic table are metals. In the modern periodic table, the metals are separated from non-metals by a zig-zag line. Some non-metals are gases, some are liquids and rest are solids at room temperature. They generally differ from metals in appearance and in other physical properties. Some elements that lie along the zig-zag line that separates metals from non-metals, have properties that fall between those of metals and non-metals. These elements are regarded as semi-metals or metalloids.
(i) From the given set of metals and non-metals, identify the non-metals.
\(\mathrm{S}, \mathrm{Mg}, \mathrm{Al}, \mathrm{P}, \mathrm{N}, \mathrm{Na}, \mathrm{K}\)

(a) S, P, K (b) Mg, AI, Na

(c) S, P, N (d) S, AI, K

(ii) Which of the following groups contains metals, non-metals and metalloids?

(a) Group 1 (b) Group 17

(c) Group 14 (d) Group 2

(iii) Which of the following elements is a metalloid?

a) Pb (b) Sb

(c) Bi (d) Zn

(iv) Silicon is a metalloid because
(a) its valency is 4
(b) it has three electron shells
(c) it shows properties of both metals and non-metals
(d) it is a liquid metal
(v) The lightest metal is

(a) Li (b) Fe

(c) Cu (d) Ag

CBSE 10th Standard Science Subject Periodic Classification of Elements Chapter Case Study Questions 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)
Generally metals possessing 1, 2 or 3 electrons in their respective valence shells have a strong tendency to lose electrons to form positive ions. Non-metals, on the other hand, having 4 to 8 electrons in their respective outermost shells generally have a tendency to gain electrons to form negative ions. Metallic character is called electropositive character and non-metallic character is called electronegative character. The metallic character increases down a group and non-metallic character increases along a period.
(i) Which of the following electronic configurations represent most electropositive element?

(a) 2,1 b) 2,8,1

(c) 2,2 (d) 2,8,2

(ii) Considering the elements B, C, N, F and Si, the correct order of their non-metallic character is

(a) B>C>Si>N>F b) Si>C>B>N>F

c) F>N>C>B>Si (d) F>N>C>Si>B

(iii) Which of the following is least metallic?

(a) N (b) P

(c) As (d) Sb

(iv) To which of the following categories does the element with atomic number 14 belong?

(a) Metal (b) Metalloid

(c) Non-metal (d) Left-hand side element

(v) Non-metals are present in the periodic table at

(a) right side (b) left side

(c) middle (d) both right and left
2)
The distance between the centre of the nucleus and the outermost shell of electrons is known as atomic radius.On moving from left to right along a period, atomic radii decrease because effective nuclear charge increases.
For example, the atomic size decreases regularly from Li to F in the second period and from Na to CI in the third period. It may, however, be noted that in any period, the noble gas has the largest size. On moving down in a group, atomic radii increase.

(i) Which of the following has the maximum atomic radius?

(a) Al (b) Si

(c) P (d) Mg

(ii) The element with the smallest size in group l3 is

(a) gallium (b) thallium

(c) aluminium (d) boron

(iii) The atomic radius decreases as we move across a period because
(a) atomic mass increases
(b) atomic number decreases
(c) effective nuclear charge increases
(d) electrons are removed
(iv) In the third period of the periodic table, the element having smallest size is

(a) Na (b) Ar

(c) CI (d) Si

(v) Among O, C, F, CI, Br, the correct order of increasing atomic radii is

(a) F, O, C, CI, Br (b) F, C, O, CI, Br

(c) F, Cl, Br, O, C (d) C, O, F, Cl, Br
3)
Study the following table in which positions of six elements A, B, C, D, E and F are shown as they are in the modern periodic table:

(i) Which element in the given table has same number of electrons as in K⁺and CI^-.

(a) C (b) F

(c) E (d) D

(ii) The formula of the oxide of element D will be

(a) DO (b) D₂O

(c) D₂O₃ (d) D₂O₅

(iii) Which of the following elements has most metallic character?

(a) F (b) D

(c) E (d) B

(iv) Element E forms a chloride with formula

(a) ECl₂ (b) ECl₃

(c) ECl₄ (d) ECI

(v) Which of the following elements is a metalloid?

(a) A (b) B

(c) C (d) E
4)
The recurrence of properties of the elements after a certain regular intervals, when they are arranged in the increasing order of their atomic numbers, is called periodicity. There are a number of physical properties such as atomic size, metallic and non -metallic character, etc. which show periodic variation. In periodic table, various properties vary differently from moving left to right in a period and going down in a group. In a period, properties vary because from moving left to right in a period, number of shells remain same but valence electron increases by one number hence nuclear charge increases. In a group, on going down, number of valence shells increases while number of valence electrons remains same.
(i) From top to bottom in a group of the periodic table, the electropositive character of the element

(a) increases (b) decreases

(c) remains unchanged (d) changes irregularly

(ii) Which element has the largest size in the second period?

(a) N (b) F

(c) Li (d) Be

(iii) Which of the following elements has three valence electrons?

(a) Cs (b) Ca

(c) Al (d) S

(iv) In the periodic table, the metallic character of elements
(a) decreases from left to right and decreases down the group
(b) decreases from left to right and increases down the group
(c) increases from left to right and increases down the group
(d) increases from left to right and decreases down the group
(v) Which of the following increases along the period?

(a) Number of valence electrons (b) Atomic size

(c) Electropositive character (d) All of these
5)
"Properties of elements are the periodic function of their atomic numbers".This is known as modern periodic law. It means that the properties of elements depend on their atomic numbers and the elements are given positions in the periodic table on the basis of their increasing atomic number. Atomic number determines the distribution of electrons in the orbit, and electrons of the outermost orbit determine the properties of an element. There are 18 groups (vertical columns) and 7 periods (horizontal lines) in modern form of the periodic table. The number of the period is equal to the number of shells in the atoms of the elements belonging to that period.
(i) What is the atomic number of element of period 3 and group 17?

(a) 10 (b) 14

(c) 17 (d) 12

(ii) Atomic number of an element is 2, 8, 6. Its period number and valency are respectively

(a) 3,2 (b) 6,6

(c) 6,2 (d) 2,2

(iii) An element has mass number 40 and contains 20 neutrons in its atom. To which period and group of the periodic table does it belong?

(a) Period-3, Group-3 (b) Period-4, Group-3

(c) Period-3, Group-2 (d) Period-4, Group-4

(iv) An elements 'X' has an atomic number of 16. With which of the following elements will it show similar chemical properties?

(a) Ne (10) (b) N (7)

(c) O (8) (d) Be (4)

(v) Identify the statement(s) which is(are) true for the modern periodic table.
(a) It reflects trends in physical and chemical properties of the elements.
(b) It helps to reflect the relative atomicity of bonds between any two elements.
(c) It helps to predict the stable valency state of the elements.
(d) All of these

CBSE 10th Standard Science Subject Carbon and Its Compounds Chapter Case Study Questions With Solution 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

A series of organic compounds having same functional group, with similar or almost identical chemical characteristics in which all the members can be represented by the same general formula and the two consecutive members of the series differ by -CH₂ group or 14 mass unit in their molecular formulae is called a homologous series. For example, all the members of alcohol family can be represented by the general formula, C_nH_2n+1 OH where, n may have the values 1, 2, 3, ... etc. The various members of a particular homologous series are called homologues. The physical properties such as density, melting point, boiling point, solubility, etc. of the members of a homologous series show almost regular variation in ascending or descending the series.
(i) Which of the following is not a characteristic of members of a homologous series?

(a) They possess varying chemical properties.

(b) Their physical properties vary in regular and predictable manner.

(c) Their formulae fit the general molecular formula.

(d) Adjacent members differ by one carbon and two hydrogen atoms.

(ii) All the members of homologous series of alkynes have the general formula

(a) C_nH_2n	(b) C_nH_2n+2
(c) C_nH_2n-2	(d) C_nH_2n-4

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

(a) A common functional group is present in different members of a homologous series..

(b) Two consecutive members of a homologous series differ by a -CH₃ group

(c) The molecular mass of a compound in the series differs by 14 a.m.u. from that of its neighbour.

(d) All the members of a homologous series have common general methods of preparation.

(iv) Identify the correct statements.
(I) As the molecular mass increases in any homologous series, a gradation in physical properties is seen.
(II) The melting and boiling points decrease with increasing molecular mass.
(III) Other physical properties such as solubility in a particular solvent decreases with increasing molecular mass.
(IV)The chemical properties, which are determined solely by the functional group, remain similar in a homologous series

(a) (II) and (III)	(b) (II) and (IV)
(c) (I), (III) and (IV)	(d) (I), (II), (III) and (IV)

(v) The table shows the formulae of three organic compounds that belong to the same homologous series.

First member of the homologous series	CH₃ -O-CH₃
Second member of the homologous series	CH₃CH₂ -O-CH₃
Third member of the homologous series	CH₃CH₂CH₂-O-CH₃

What is the general formula of this series?

(a) C_nH_2nO	(b) C_nH_2n+2O
(c) C_nH_2nOH	(d) C_nH_2n+2OH

2)

When an element exists in two or more different forms in the same physical state, these different forms are called allotropes and the phenomenon is known as allotropy. Allotropes have similar chemical properties but theydiffer in their physical properties. Carbon exists in crystalline and amorphous forms. In crystalline form, it occurs as diamond, graphite and fullerenes. Diamond is a colourless, transparent substance having extraordinary brilliance. It is the hardest natural substance known. It is used for cutting marble, granite and glass. Graphite is a greyish-black, opaque substance. It is lighter than diamond i.e., it has lower density. It has sheet like structure having hexagonal layers. One layer slides over the other layer which makes it soft to touch. It is the reason that graphite is used as a lubricant.
(i) Substance X is a moderate conductor of electricity. Substance X has the structure shown below:

Which statements about substance X are correct?
(I) It is a covalent compound.
(II) It has a giant molecular structure.
(III) It has the same structure as graphite
(IV) It has the same structure as diamond

(a) (I) and (III)	(b) (II) and (III)
(c) (II) and (IV)	(d) (I), (II) and (IV)

(ii) Which of the following is correct about the structure of diamond?

(a) Carbon atoms are held together by single covalent bonds.

(b) Electrons move freely through the structure.

(c) Layers of atoms slide easily over each other.

(d) Carbon atoms conduct electricity in the molten state.

(iii) Which three allotropes of carbon, do the given figure reopresents.

(I)	(II)	(III)
(a) Diamond	Graphite	Buckminster fullerene
(b) Graphite	Buckminster fullerene	Diamond
(c) Diamond	Buckminster fullerene	Graphite
(d) Graphite	Diamond	Buckminster fullerene

(iv) Identify the incorrect statement(s).
(I) Diamond is the hardest substance known while graphite is smooth and slippery.
(II) Diamond is made up of billions of carbon atoms. Each carbon atom is bonded to four other carbon atoms in a tetrahedral manner to form a giant lattice. All carbon atoms are bonded by strong covalent bonds.
(III) Graphite is a poor conductor of electricity unlike other non-metals.
(IV) Graphite has a giant covalent structure that is made up of layers of carbon atoms. In each layer, each carbon atom is bonded to three other carbon atoms to form hexagonal rings of carbon atoms.

(a) (1) and (III)

(b) Only (III)

(c) (II) and (IV)

(d) (1), (II) and (IV)

(v) Structures Qf two different forms of carbon are given below:

Identify the two forms (I and II respectively) and how are they related to each other?

(a) Diamond, Graphite, Isotopes of carbon	(b) Graphite, Diamond, Allotropes of carbon
(c) C₁₂ , C₁₄, Allotropes of carbon	(d) C ₁₄, C₁₂ , Isotopes of carbon

3)
As neutral atom carbon has electronic configuration K L. To gain inert gas configuration carbon can either 2, 4 donate 4 valence electrons (helium gas configuration) or gain 4 electrons (neon gas configuration), but it cannot do so. To acquire inert gas configuration carbon can only share its 4 valence electrons with other atoms forming covalent bonds. A covalent bond can be defined as a chemical bond formed between two atoms by mutual sharing of valence electrons so that each atom acquires the stable electronic configuration of the nearest noble gas. The concept of covalent bonds was given by Langmuir and Lewis to explain bonding in non-ionic compounds. The covalent bonds are of three types. If each atom contributes one electron, the covalent bond formed is called a single covalent bond and is represented by a single line (-) and if each atom contributes two electrons, the covalent bond formed is called a double bond and is represented by a double line (=) and if each atom contributes three electrons, the covalent bond formed is called a triple bond and is represented by a triple line (=).
(i) Which of the following do not contain a double bond?
I. S02
II. NH3
III. HCl
IV. 02

(a) I and II only (b) II and III only (c) III and IV only (d) I and IV only

(ii) Which of the following contains a triple bond?

(a) N₂ (b) O₂ (c) CO₂ (d) H₂

(iii) The shared pair of electrons is said to constitute a _______________ bond between two hydrogen atoms.

(a) single (b) double (c) triple (d) ionic

(iv) Which of the following molecules has all its atoms joined together by double covalent bonds?

(a) Methane (b) Water (c) Carbon dioxide (d) Nitrogen trichloride

(v) Chlorine forms a diatomic molecule, Cl₂ . The electron dot structure for this molecule is
4)
Two allotropic forms of carbon which are crystalline in nature, are diamond and graphite. They differ physically but chemically they are similar. Diamond is the hardest crystalline form of carbon. In diamond, each carbon atom is linked to four other carbon atoms by covalent bonds. In graphite, each carbon atom is linked to three other carbon atoms by covalent bond. Graphite is relatively soft and greasy. It is also a good conductor of electricity. The C-C bond length in graphite is 141.5 pm while in diamond it is 154 pm.
(i) Which of the following is a good conductor of heat and electricity?

(a) Coal (b) Diamond (c) Charcoal (d) Graphite

(ii) Graphite is a good conductor of electricity because

(a) it has free electrons (b) it has free atoms (c) it is crystalline (d) it is soft and greasy.

(iii) Which of the following types of binding forces is present in the structure of diamond?

(a) Ionic (b) van der Waals' (c) Covalent (d) None of these

(iv) Diamond is not a good conductor of electricity because

(a) it is very hard (b) its structure is very compact

(c) it is not water soluble (d) it has no free electron.

(v) Which of the following is the structure of diamond?
5)
The compounds which have the same molecular formula but differ from each other in physical or chemical properties are called isomers and the phenomenon is called isomerism. When the isomerism is due to difference in the arrangement of atoms within the molecule, without any reference to space, the phenomenon is called structural isomerism. In other words, structural isomers are compounds that have the same molecular formula but different structural formulas, i.e., they are different in the order in which different atoms are linked. In these compounds, carbon atoms can be linked together in the form of straight chains, branched chains or even rings.
(i) Which of the following sets of compounds have same molecular formula?

(a) Butane and iso-butane (b) Cyclohexane and hexene

(c) Prop anal and propanone (d) All of these

(ii) In order to form branching, an organic compound must have a minimum of

(a) four carbon atoms (b) three carbon atoms

(c) five carbon atoms (d) any number of carbon atoms.

(iii) Which of the following is an isomeric pair?

(a) Ethane and propane (b) Ethane and ethene

(c) Propane and butane (d) Butane and 2-methylpropane

(iv) Among the following the one having longest chain is

(a) neo-pentane (b) iso-pentane

(c) 2-methylpentane (d) 2, 2-dimethylbutane.

(v) The number of isomers of pentane is

(a) 2 (b) 3 (c) 4 (d) 5

CBSE 10th Standard Science Subject Carbon and Its Compounds Chapter Case Study Questions 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)
Study the table related to three hydrocarbons A, B, C and answer the questions that follow.

Organic compound Molecular formula

A C₃H₅

B C₅H₁₀

C C₄H₆

(i) A, Band C are classified as hydrocarbons because

(a) they contain hydrogen (b) they contain carbon

(c) they contain both carbon and hydrogen (d) none of these.

(ii) Which of these organic compounds is an alkyne?

(a) A (b) B (c) C (d) All of these

(iii) C₅H₁₀belongs to

(a) C_nH_2n+2 series (b) C_nH_2n series

(c) C_nH_2n-2series (d) none of these.

(iv) Identify the incorrect statement about these three hydrocarbons.

(a) All have different general formula. (b) A and B differ by -CH2 unit.

(c) C is an alkyne. (d) B is an alkene.

(v) General formula for alkane is

(a) C_nH_2n (b) C_nH_2n+2 C_nH_2n-2 (d) C_nH_n
2)

(i) Which of the following compounds belong to same homologous series?

(a) Sand T (b) Tand U (c) Pand U (d) P and T

(ii) The functional group of compound (R) is

(a) alcohol (b) aldehyde (c) ketone (d) carboxylic acid.

(iii) Compound (T) belongs to homologous series of

(a) alkynes (b) alkenes (c) alkanes (d) none of these.

(iv) Which of the 'following compounds is unsaturated hydrocarbon?

(a) S (b) Q (c) U (d) R

(v) Which of the following compounds belongs to alkane series?

(a) P (b) S (c) T (d) U

3)

The table given below shows six organic compounds A, B, C, D, E and F having different molecular formula:

Organic compound	Molecular formula
A	C7H₁₆
B	C₈H₁₆
C	C₄H₆
D	C₆H₁₀
E	C₅H₁₀
F	C₉H₂₀

(i) Which of the following compounds belong to same homologous series?

(a) E and F

(b) B and C

(c) A and B

(ii) Which of the following is the member of the same homologous series as E?

(a) D

(b) A

(c) F

(d) B

(iii) Identify the correct statements.

(a) A and F are saturated hydrocarbons while all others are unsaturated hydrocarbons.

(b) C and D belong to a homologous series having general formula C_nH_2n

(c) B and E are alkynes.

(d) All the compounds have same physical and chemical properties.

(iv) Compound B is

(a) an alkane

(b) an alkene

(c) an alkyne

(d) none of these.

(v) Compound (F) has a general formula

(a) C_nH_{2n -2}

(b) C_nH_2n

(c) C_nH_2n+4

(d) C_nH_2n+2

4)
A hydrocarbon (P) has the molecular formula C₁₀H₂₂.A hydrocarbon (Q) has two carbon atoms less than (P) and belong to the same homologous series. A hydrocarbon (R) has two carbon atoms more than (P) and belong to the same homologous series.
(i) What is the molecular formula of (Q)?

(a) C₁₂H₂₆ (b) C₈H₁₆ (c) C₈H₁₈ (d) C₈H₁₄

(ii) To which homologous series do the compound (P), (Q) and (R) belong?

(a) C_nH_2n (b) C₂H_{2n- 2} (c) C_nH_2n+2 (d) C_nH_{2n + 1}

(iii) What is the molecular formula of (R)?

(a) C₁₂H₂₆ (b) C₁₂H₂₄ (c) C₁₂H₂₂ (d) C_l2H₂₈

(iv) Identify the correct statement about compounds (P), (Q) and (R).

(a) They have same melting and boiling points. (b) They have same chemical properties.

(c) They have different general formula. (d) They differ by -CH₂ unit.

(v) Compounds (P), (Q) and (R) are

(a) alkanes (b) alkenes (c) alkynes (d) none of these.
5)
An organic molecule has the following structure:

(i) To which homologous series does this molecule belong?

(a) Aldehydes (b) Ketones (c) Alcohols (d) Alkanes

(ii) What is the general formula of this homologous series?

(a) C_nH_2n+1OH (b) C_nH_{2n + 2} (c) CnH_2nO (d) C_nH_2n+1CHO

(iii) Which is the next member of this series?

(a) C₄H₉OH (b) C₃H₇OH (c) C₅H₁₁OH (d) C₆H₁₃OH

(iv) Which is the third member of this series?

(a) C₃H₇O H (b) C₄H₉OH (c) C₂H₅OH (d) CH₃OH

(v) Which is the second member of this series?

(a) Ethanol (b) Methanol (c) Propanol (d) Butanol

CBSE 10th Standard Science Subject Metals and Non-Metals Chapter Case Study Questions With Solution 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)
The chemical reactivity of an element depends upon its electronic configuration. All elements having less than eight electrons in the outermost shell show chemical reactivity. During chemical reactions, atoms of all elements tend to achieve a completely filled valence shell. Metals are electropositive in nature. They have tendency to lose one or more electrons present in the valence shell of their atoms to form cations and achieve nearest noble gas configuration. The compounds formed by the transfer of electrons from one element to other are known as ionic or electrovalent compounds.
(i) The electronic configurations of three elements X, Y and Z are:
X : 2 Y: 2, 8, 7 Z : 2, 8, 2
Which of the following is correct regarding these elements?

(a) X is a metal. (b) Y is a metal.

(c) Z is a non-metal (d)Yis a non-metal and Z is a metal

(ii) Element X reacts with element Y to form a compound Z. During the formation of compound Z, atoms of X lose one electron each whereas atoms of Y gain one electron each. Which of the following properties is not shown by compound Z?

(a) High melting point

(b) Low melting point

(c) Occurrence as solid

(d) Conduction of electricity in molten state

(iii) Which of the following is correct representation of formation of magnesium chloride?

(d) None of these

(iv) The electronic configuration of sodium ion is

(a) 2,8,8 (b) 2,8,2. (c) 2,6 (d) 2,8.

(v)Which of the following represents an electropositive element?

(a) 2,8,6 (b) 2,8,8 (c) 2,8,8,1 (d) 2, 7
2)
The arrangement of metals in a vertical column in the decreasing order of their reactivities is called the reactivity series or activity series of metals. The most reactive metal is at the top position of the reactivity series. The least reactive metal is at the bottom of the reactivity series.
Hydrogen, though a non-metal, has been included in the activity series of metals only for comparison. Apart from it, the hydrogen atom also has tendency to lose its valence electron and form cation which behaves like metal.
\(\mathrm{H} \rightarrow \mathrm{H}^{+}+e^{-}\)
(i) Which metal can be displaced by copper from its salt solution?

(a) Zinc (b) Silver (c) Iron (d) Lead

(ii) An element 'X after reacting with acids liberates hydrogen gas and can displace lead and mercury from their salt solutions. The metal 'X is

(a) copper (b) gold (c) calcium (d) hydrogen.

(iii) the most reactive metal is

(a) potassium (b) barium (c) zinc (d) calcium

(iv) The metal which does not liberate hydrogen gas after reacting with acid is

(a) zinc (b) lead (c) iron (d) gold

(v) Which of the following metals does not react with water at all?
(I) Sodium
(II) Copper
(III) Aluminium
(IV) Lead

(a) I and III only (b) IV only (c) II and IV only (d) I, II, III and IV
3)
Metals as we know, are very useful in all fields, industries in particular. Non-metals are no less in any way. Oxygen present in air is essential for breathing as well as for combustion. Non-metals form a large number of compounds which are extremely useful, e.g., ammonia, nitric acid, sulphuric acid, etc.
Non-metals are found to exist in three states of matter. Only solid non-metals are expected to be hard however, they have low density and are brittle. They usually have low melting and boiling points and are poor conductors of electricity.
(i)____________ is a non-metal but is lustrous

(a) Phosphorus (b) Sulphur (c) Bromine (d) Iodine

(ii) Which of the following is known as 'King of chemicals'?

(a) Urea (b) Ammonia X (c) Sulphuric acid (d) Nitric acid

(iii) Which of the following non-metals is a liquid?

(a) Carbon (b) Bromine (c) Iodine (d) Sulphur

(iv) Hydrogen is used

(a) for the synthesis of ammonia (b) for the synthesis of methyl alcohol

(c) in welding torches (d) all of these

(v) Generally, non-metals are bad conductors of electricity but 'X'which is a form of carbon is a good conductor of electricity and is an exceptional non-metal. 'X'is

(a) diamond (b) graphite (c) coal (d) coke.

4)

Ionic compound is a chemical compound in which ions are held together by ionic bonds. An ionic bond is the type of chemical bond in which two oppositely charged ions are held through electrostatic forces. We know that, metal atoms have loosely bound valence electrons in their valence shell and non-metal atoms need electrons in their valence shell to attain noble gas configuration. The metal atom loses the valence electrons while non-metal atom accepts these electrons. By losing electrons, metal atoms change to cations and by accepting electrons, non-metals form anions. Ionic compounds are generally solid and exist in the form of crystal. They have high melting and boiling points.
(i) Which of the following can change to a cation?

(a) Fluorine

(b) Oxygen

(c) Potassium

(d) Neon

(ii) Which of the following can change to an anion?

(a) Iodine

(b) Magnesium

(c) Calcium

(d) Xenon

(iii) Ionic compounds are soluble in _____________.

(a) Kerosene

(b) Petrol

(c) Water

(d) None of these

(iv) Which of the following statements is correct about ionic compounds?
I. They conduct electricity in solid state.
II. They conduct electricity in solutions.
III. They conduct electricity in molten state.

(a) I only

(b) II only

(c) III only

(d) II and III only

(v) Select the incorrect statement.

(a) Ionic compounds are generally brittle

(b) Ions are the fundamental units of ionic compounds

(c) Formation of ionic bonds involve sharing of electrons

(d) NaCl is an ionic compound.

5)
An element is a pure substance made up of same kind of atoms. At present, nearly 118 elements are known but all of them do not occur free in nature, some of them have been synthesized by artificial methods. Based on their properties, they are mainly classified as metals and non-metals. Metals are those elements which lose electrons and form positive ions i.e., they are electropositive in nature. They are generally hard, good conductors of heat and electricity, malleable, ductile and have striking lustre. They have a significant role to play in our daily life.
(i) Metals which are of vital importance to the national defence, energy and industry sector are called strategic metals. Which of the following is a strategic metal?

(a) Titanium (b) Zirconium (c) Manganese (d) All of these

(ii) Which metal is the best conductor of electricity?

(a) Silver (b) Platinum (c) Nickel (d) Iron

(iii) Which of the following metals is not a coinage metal?

(a) Copper (b) Silver (c) Iron (d) Gold

(iv) Which of the following are the most malleable metals?
(I) Sodium
(II) Gold
(III) Potassium
(IV) Silver

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

Identify the correct statement(s).
(I) The wires that carry current in our homes have a coating of PVC or a rubber like material.
(II) School bells are made of metals.
(III) Metals do not conduct electricity.
(IV) Metals which produce a sound on striking a hard surface are said to be non-sonorous.

(a) (I) and (III) (b) (I) and (II) (c) (III) and (IV) (d) Only (II)

CBSE 10th Standard Science Subject Metals and Non-Metals Chapter Case Study Questions 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

The chemical properties of metals are mostly linked with the electron releasing tendency of their atoms. Greater the tendency, more will be the reactivity of the metal. They react with oxygen, water, hydrogen, acids, etc. Since they can lose electrons, they act as reducing agents. Some reactions of metals are given as :
Metal + Oxygen \(\longrightarrow\) Metal oxide
Metal + Water \(\longrightarrow\)7 Metal hydroxide + Hydrogen ..
Metal + Acid_(dilute)\(\longrightarrow\)7 Metal salt + Hydrogen
Metal X + Salt solution of metal Y \(\longrightarrow\)7 Salt solution of X + Y (Displacement reaction).
(i) Metals such as _________ and __________ react so vigorously that they catch fire if kept in the open. Hence, to protect them and to prevent accidental fires, they are kept immersed in _____________.

(a) phosphorus, magnesium, water	(b) sodium, potassium, kerosene oil
(c) sodium, potassium, water	(d) tin, lead, alcohol

(ii) Which of the following pairs will give displacement reaction?

(a) NaCl solution and copper metal	(b) MgCl₂ solution and aluminium metal
(c) FeSO₄solution and silver metal	(d) AgNO₃solution and copper metal

(iii) There are four metals K, L, M and N. Identify them by using the hints given below.
K forms basic oxide.
L forms amphoteric oxide.
Oxide of M dissolves in water to form alkali.
N does not react with water at all.

\({ (a) } K \rightarrow \mathrm{Zn}, L \rightarrow \mathrm{Al}, M \rightarrow \mathrm{Na}, N \rightarrow \mathrm{Fe}\)	\({ (b) } K \rightarrow \mathrm{Fe}, L \rightarrow \mathrm{Na}, M \rightarrow \mathrm{K}, N \rightarrow \mathrm{Zn}\)
\({ (c) } K \rightarrow \mathrm{K}, L \rightarrow \mathrm{Cu}, M \rightarrow \mathrm{Pb}, N \rightarrow \mathrm{Na}\)	\({ (d) } K \rightarrow \mathrm{Cu}, L \rightarrow \mathrm{Zn}, M \rightarrow \mathrm{K}, N \rightarrow \mathrm{Pb}\)

(iv) Which metal does not react with dilute hydrochloric acid?

(a) Iron

(b) Sodium

(c) Zinc

(d) Copper

(v) Food cans are coated with tin and not with zinc because

(a) zinc is costlier than tin	(b) zinc has a higher melting point than tin
(c) zinc is more reactive than tin	(d) zinc is less reactive than tin.

2)

On the basis of reactivity of different metals with oxygen, water and acids as well as displacement reactions, the metals have been arranged in the decreasing order of their reactivities. This arrangement is known as activity series or reactivity series of metals.
The basis of reactivity is the tendency of metals to lose electrons. If a metal can lose electrons easily to form positive ions, it will react readily with other substances. Therefore, it will be a reactive metal. On the other hand, if a meal loses electrons less rapidly to form a positive ion, it will react slowly with other substances. Therefore, such a metal will be less reactive.
(i) Which of the following metals is less reactive than hydrogen?

(a) Copper

(b) Zinc

(c) Magnesium

(d) Lead

(ii) Which of the following metals is more reactive than hydrogen?

(a) Mercury

(b) Platinum

(c) Iron

(d) Gold

(iii) Which of the following metals reacts vigorously with oxygen?

(a) Zinc

(b) Magnesium

(c) Sodium

(d) Copper

(iv) Which of the following represents the correct order of reactivity for the given metals?

\({ (a) } \mathrm{Na}>\mathrm{Mg}>\mathrm{Al}>\mathrm{Cu}\)

\({ (b) } \mathrm{Mg}>\mathrm{Na}>\mathrm{Al}>\mathrm{Cu}\)

\({ (c) } \mathrm{Na}>\mathrm{Mg}>\mathrm{Cu}>\mathrm{Al}\)

\({(d) } \mathrm{Mg}>\mathrm{Al}>\mathrm{Na}>\mathrm{Cu}\)

(v) Hydrogen gas is not evolved when a metal reacts with nitric acid. It is because HNO₃is a strong oxidising agent. It oxidises the H₂ produced to water and itself gets reduced to any of the nitrogen oxides (N₂O, NO, NO₂ ). But ___________ and ___________ react with very dilute HNO₃to evolve H₂gas.

(a) Pb, Cu

(b) Na, K

(c) Mg, Mn

(d) AI, Zn

3)
Non-m;tals are highly electronegative in nature. They have a tendency to gain electrons in their valence shell to achieve nearest noble gas configuration. Thus, they form anions and act as good oxidising agents.
\(X \quad+n e^{-} \longrightarrow X^{n-}\)
(non-metal atom) (anion)
They react with air or oxygen on heating to form oxides which react with water to form acids. Thus, nonmetal oxides are acidic in nature. Non-metals do not react with dilute acids at all. This is because they are electronegative and therefore, cannot displace hydrogen from acids but they form covalent hydrides when heated with hydrogen.
(i) The acid formed when sulphur trioxide reacts with water is

(a) sulphurous acid (b) sulphuric acid (c) both (a) and (b) (d) none of these

(ii) An element 'X' forms an oxide XO₂ , which is a very useful gas used in the process of photosynthesis. The element 'X' is

(a) sulphur (b) nitrogen (c) carbon (d) phosphorus

(iii) Non-metals generally act as

(a) oxidising agents (b) reducing agents (c) both (a) and (b) (d) none of these

(iv) Which of the following elements produces basic oxide on reacting with oxygen?

(a) Chlorine (b) Sulphur (c) Phosphorus (d) Magnesium

(v) Which of the following is a covalent hydride?

(a) CH₄ (b) NH₃ (c) H₂S (d) All of these

4)

Although there is no sharp line of distinction between metals and non-metals yet there are some distinctive differences. The main points of differences are:

Property	Metals	Non-metals
Electronic structure	They have 1 to 3 electrons in the outermost shell of their atoms	They have 4 to 8 electrons in the outermost shell of their atoms.
State of existence	They are mostly solid at room temperature except mercury and gallium which are liquid.	They are either solids or gases at room temperature (except bromine which is a liquid).
Density	They have high density.	They have low density.
Nature of ions	They are electropositive elements and hence, lose one or more electrons to form positive ions.	They are electronegative elements and hence, gain one or more electrons to form negative ions.
Nature of chlorides	They generally combine with chlorineto form solid ionic chlorides which conduct electricity in the aqueous solution or in the molten state.	They combine with chlorine to form covalen chlorides. These are either gases or liquids. Non-metal chlorides do not contain ions, therefore, they do not conduct electricity.
Nature of oxides	They form basic oxides, though some oxides are amphoteric also.	They form acidic or neutral oxides.
Displacement of hydrogen from acids	Metals which lie above hydrogen in the reactivity series displace hydrogen from acids.	They do not displace hydrogen from acids.

(i) Match column-I with column-Il and select the correct option using the given code

Column-I	Column-II
P. A metal that forms amphoteric oxides	(I) Ga
Q. A metal which melts when keep on our palm	(II) Au
R. A metal that has highest density	(III) Al
S. A metal which cannot displace hydrogen from acids	(IV) Os

(a) P-(II), Q-(I), R-(lII), S-(lV)	(b) P-(III), Q-(I), R-(IV), S-(lI)
(c) P-(lV), Q-(II), R-(lII), S-(I)	(d) P-(lII), Q-(II), R-(I), S-(lV)

(ii) State True (T) or False (F) for the following statements.
(I) Non-metals react with acids to give a salt and hydrogen gas.
(II) Zinc oxide is amphoteric in nature.
(III) Copper oxide is basic in nature.
(IV) Hydrogen gas is evolved when a metal reacts with dilute acid.
(V) Copper reacts vigorously with dilute HCl.

	(I)	(II)	(III)	(IV)	(V)
(a)	F	F	F	T	T
(b)	T	F	T	F	F
(c)	F	T	F	F	T
(d)	F	T	T	T	F

(iii) Tick (✓) the correct statements and cross (x) the incorrect statements.
(I) Non-metals are either solids or gases except mercury which is a liquid.
(II) Sodium is a metal and can lose its electrons easily.
(III) Most non-metals produce acidic oxides when dissolved in water. Most metals produce basic oxides on reaction with water.
(IV) Graphite is a conductor of electricity.

	(I)	(II)	(III)	(IV)
(a)	✓	メ	✓	メ
(b)	メ	✓	メ	✓
(c)	メ	✓	✓	✓
(d)	メ	✓	✓	メ

(iv) An element X (atomic number 12) reacts with another element Y (atomic number 17) to form a compound Z. Which of the following statements are true regarding this compound?
I. Molecular formula of Z is XY₂
II. It is soluble in water.
III. X and Yare joined by sharing of electrons.
IV. It would conduct electricity in the molten state.

(a) II and III only

(b) I and II only

(c) I, III and IV only

(d) I, II and IV only

(v) Which of the following metals form an amphoteric oxide?

(a) Zn

(b) Ca

(c) Na

(d) Cu

5)

Sample pieces of five metals P, Q, R, Sand T are added to the tabulated solutions separately. The results observed are shown in the table given below:

Metal	Solutions
Metal	CuSO₄	ZnSO₄	FeSO₄	AgNO₃
P	No change	No change	No change	A coating on metal
Q	Brown coating	___	Grey deposit	A coating on metal
R	No change	No change	No change	No change
S	___	No change	No change	Brown deposit
T	Brown deposit	New coating	New coating	New coating

Based on the observations recorded in the table answer the following questions:
(i) Which is the most reactive metal?

(a) Q

(b) R

(c) S

(d) T

(ii) Which is the least reactive metal?

(a) P

(b) R

(c) T

(d) Q

(iii) Activity series of elements is

(a) the arrangement of elements in increasing order of reactivity.

(b) the arrangement of elements in decreasing order of reactivity.

(c) the arrangement of oxides of elements in increasing order of reactivity

(d) none of these.

(iv) Which of the following metal is least reactive?

(a) Zn

(b) Cu

(c) Ag

(d) Fe

(v) Decreasing order of reactivity is

(a) P> Q> R > S> T	(b) Q > T > R > S > P
(c) T>Q>S>P>R	(d) S > R > Q> T> P

CBSE 10th Standard Science Subject Acids, Bases and Salts Chapter Case Study Questions With Solution 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

The acidic behaviour of acids is due to the presence of hydrogenil(H⁺)ions in them. They produce hydrogen ions in the presence of water. Water is a polar solvent and this property of water helps in weakening the bond between the ions and makes them soluble. Hence, acids and bases produce ions in aqueous solutions.
It may be noted that a dry Hel gas or a solution of hydrogen chloride in organic, nonpolar solvents like toluene or benzene do not show acidic properties. This is because hydrogen chloride does not undergo ionization in toluene.
The reason why Hel splits into H⁺and CI^-ions in presence of water lies in the fact that water molecules, being polar, pull the H⁺and Cl^-ions apart and thus, the bond in Hel is broken

(i) Identify the wrong statement.

(a) Higher the hydronium ion concentration, lower is the pH value

(b) Universal indicator is used to judge how strong a given acid or base is

(c) As the pH value increases from 7 to 14, it represents increase in H⁺ ion concentration in the solution

(d) Value less than 7 on the pH scale represents an acidic solution

(ii) If the pH of a solution is 8, then its [H⁺] ion is

(a) log 10^{- 8}

(b) 10⁸

(c) 10^{- 8}

(d) 8

(iii) In terms of acidic strength, which one of the following is in the correct increasing order?

(a) Water < Acetic acid < Hydrochloric acid	(b) Water < Hydrochloric acid < Acetic acid
(c) Acetic acid < Water < Hydrochloric acid	(d) Hydrochloric acid < Water < Acetic acid

(iv) Which of the following compounds does not give H⁺ ions in aqueous solution?

(a) H₃PO₄

(b) C₂H₅OH

(c) H₂CO₃

(d) CH₃COOH

(v) Four solutions labelled as P, Q, Rand Shave pH values 1, 9, 3 and 13 respectively.
Which of the following statements about the given solutions is incorrect?

(a) Solution P has higher concentration of hydrogen ions than solution R.

(b) Solution Q has lower concentration of hydroxide ions than solution S.

(c) Solutions P and Q will turn red litmus solution blue.

(d) Solution P is highly acidic while solution Q is weakly basic.

2)
A compound, X of sodium forms a white powder. It is a constituent of baking powder and is used in some antacids. When heated it gives a compound, Y which is anhydrous and absorbs water to become a hydrated salt. When this salt is kept in open air, it loses water molecules in a process called efflorescence. When dissolved in water it forms a strong base and a weak acid, Z.
(i) What is the compound, X?

(a) NaHCO₃ (b) Na₂CO₃ (c) NaOH (d) NaCl

(ii) The compound, Y is

(a) NaHCO³ (b) Na₂CO₃ (c) Na₂CO₃ 10H₂O (d) NaCI

(iii) What is the nature of the solution formed by dissolving Y in water?

(a) Alkaline (b) Acidic (c) Neutral (d) It remains insoluble

(iv) Identify the compound, Z.

(a) CO₂ (b) H₂CO₃ (c) NaOH (d) H₂O

(v) Sodium carbonate is a basic compound because it is a salt of a

(a) strong acid and strong base (b) weak acid and weak base

(c) strong acid and weak base (d) weak acid and strong base

3)

Sodium chloride obtained from sea water or from lakes contains many impurities such as sulphates of sodium and magnesium along with chlorides of calcium and magnesium. The chlorides of calcium and magnesium are particularly undesirable on account of their deliquescent nature.
For its purification, common salt is dissolved in minimum quantity of water to get a saturated solution from which insoluble impurities are filtered off. Then hydrogen chloride gas is passed through the saturated solution and the crystals of pure NaCl separate out. The soluble impurities remain in the mother liquor. The crystals are filtered, washed and dried.
(i) Select the correct statement regarding salt NaCl.

(a) Pure NaCI is hygroscopic in nature

(b) It is soluble in alcohol

(c) Pure NaCI is not hygroscopic, it shows hygroscopic nature due to impurities

(d) It is a brown crystalline solid

(ii) Nature of aqueous solution of common salt is

(a) acidic

(b) alkaline

(c) basic

(d) neutral

(iii) In the given series of reactions, Y and Z respectively are
²

(a) NaHCO₃ , NaOCl₂

(b) NH₄CI, Na2CO₃

(c) Na₂CO₃, NH₄CI

(d) Na₂CO₃, NaHCO₃

(iv) Which of the following compounds is alkaline in aqueous medium?

(a) Na₂CO₃

(b) NaCI

(c) H₂CO₃

(d) CuSO₄

(v) Some statements regarding salt NaCI are given below
(I) It is prepared by chlor-alkali process
(II) It is a white crystalline substance
(III) It also exists in the form of rocks and is called rock salt
(IV) It is a neutral salt, pH value of NaCI is 7

(a) II and III only

(b) III and IV only

(c) I and IV only

(d) II, III and IV only

4)

Chemically, Plaster of Paris (POP) is calcium sulphate hemihydrate, i.e., containing half molecule of water of crystallisation. It is represented by the formula, CaSO_{4 ·}1/2H₂O. Half molecule of water of crystallisation means that one water molecule is shared by two formula units of CaSO_4. Hence, we also represent its formula as (CaSO₄)_2·H₂O. The name, plaster of Paris, was given to this compound because for the first time, it was made from gypsum which was mainly found in Paris.
(i) The difference of water molecules in gypsum and plaster of Paris is

(a) 5/2

(b) 2

(c) 1/2

(d) 3/2

(ii) Plaster of Paris hardens by

(a) giving off CO₂	(b) changing into CaCO₃
(c) combining with water	(d) giving out water

(iii) Which of the following statements is incorrect?

(a) Plaster of Paris is used to ornate designs on walls and ceilings

(b) On heating gypsum above 373 K, CaSO₄ is obtained

(c) Dead burnt plaster is CaSO₄·2H₂O

(d) Setting of plaster is due to its hydration into gypsum

(iv) Select the incorrect statement with respect to gypsum

(a) It is slightly soluble in water

(b) It is also known as alabaster

(c) On heating gypsum at 373 K, it loses water molecules and becomes calcium sulphate hemihydrate

(d) Chemical formula of gypsum is CaSO₄ ·1/2H₂O

(v) Plaster of Paris is obtained by

(a) adding water to calcium sulphate.

(b) adding sulphuric acid to calcium hydroxide

(c) heating gypsum to a very high temperature

(d) heating gypsum to 100° C

5)

pH is quite useful to us in a number of ways in daily life. Some of its applications are:
Control of pH of the soil: Plants need a specific pH range for proper growth. The soil may be acidic, basic or neutral depending upon the relative concentration of H⁺ and OH^-. The pH of any soil can be determined by using pH paper. If the soil is too acidic, it can be corrected by adding lime to it. If the soil is too basic, it can be corrected by adding organic manure which contains acidic materials
Regaining shine of a tarnished copper vessel by use of acids: A copper vessel gets tarnished due to formation of an oxide layer on its surface. On rubbing lemon on the vessel, the surface is cleaned and the vessel begins to shine again. This is due to the fact that copper oxide is basic in nature, which reacts with the acid (citric acid) present in lemon to form a salt (copper citrate) which is washed away with water. As a result, the layer of copper oxide is removed from the surface of the vessel and the shining surface is exposed
(i) When black copper oxide placed in a beaker is treated with dilute HCl, its colour changes to

(a) white (b) dark red

(c) bluish green

(d) no change

(ii) P is an aqueous solution of acid and Q is an aqueous solution of base. When these two are diluted separately, then

(a) pH of P increases while that of Q decreases till neutralisation

(b) pH of P decreases while that of Q increases till neutralisation

(c) pH of both P and Q decrease

(d) pH of both P and Q increase

(iii) Which of the following acids is present in bee sting?

(a) Formic acid (c) Citric acid	(b) Acetic acid
(b) Acetic acid	(d) Hydrochloric acid

(iv) Sting of ant can be cured by rubbing the affected area with soap because

(a) it contains oxalic acid which neutralises the effect of formic acid

(b) it contains aluminium hydroxide which neutralises the effect of formic acid

(c) it contains sodium hydroxide which neutralises the effect of formic acid

(d) none of these

(v) The pH of soil X is 7.5 while that of soil Y is 4.5. Which of the two soils, should be treated with powdered chalk to adjust its pH?

(a) X only

(b) Y only

(c) Both X and Y

(d) None of these

CBSE 10th Standard Science Subject Acids, Bases and Salts Chapter Case Study Questions 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

Baking powder produces carbon dioxide on heating, so it is used in cooking to make the batter spongy. Although, baking soda also produces CO₂on heating, but it is not used in cooking because on heating, baking soda produces sodium carbonate along with carbon dioxide. Sodium carbonate, thus, produced, makes the taste bitter. Baking powder is the mixture of baking soda and a mild edible acid. Generally, tartaric acid is mixed with baking soda to make baking powder. When baking powder is heated, NaHCO₃ decomposes to give CO₂ which makes bread and cake fluffy. Tartaric acid helps to remove bitter taste due to formation of sodium tartrate.
\(2 \mathrm{NaHCO}_{3}+ \ \ \mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{6} \quad \longrightarrow \quad 2 \mathrm{CO}_{2}+2 \mathrm{H}_{2} \mathrm{O}+\mathrm{Na}_{2} \mathrm{C}_{4} \mathrm{H}_{4} \mathrm{O}_{6}\)
Baking soda Tartaric acid Carbon dioxide Sodium tartrate
(i) On passing excess CO₂ gas in aqueous solution of sodium carbonate, the substance obtained is

(a) NaOH	(b) NaHCO₃
(c) Na₂CO₃·10H₂O	(d) Na2CO₃ ·H₂O

(ii) When sodium hydrogen carbonate is added to acetic acid, it evolves a gas. Which of the following statements are true about the gas evolved?
(I) It turns lime water milky
(II) It extinguishes a burning splinter
(III) It dissolves in a solution of sodium hydroxide
(IV) It has a pungent odour

(a) (I) and (II)	(b) (I), (II) and (III)
(c) (II), (III) and (IV)	(d) (I) and (IV)

(iii) Select the correct statement regarding sodium hydrogen carbonate.

(a) CO and CO₂ are produced during the heating ofNaHCO₃

(b) It is insoluble in water.

(c) It is used in soda-acid fire extinguishers.

(d) All of these

(iv) Acetic acid was added to a solid X kept in a test tube. A colourless and odourless gas was evolved. The gas was passed through lime water which turned milky. It was concluded that

(a) solid X is sodium hydroxide and the gas evolved is CO₂

(b) solid X is sodium bicarbonate and the gas evolved is CO₂

(c) solid X is sodium acetate and the gas evolved is CO₂

(d) solid X is sodium chloride and the gas evolved is CO₂

(v) Which of the following statements are correct regarding baking soda?
(I) Baking soda is sodium hydrogen carbonate
(II) On heating, baking soda gives sodium carbonate
(III) It is used for manufacture of soap
(IV) It is an ingredient of baking powder

(a) I and IV only	(b) I, II and III only
(c) I, II and IV only	(d) I, II, III and I

2)

Bleaching powder is also known as chloride of lime. It is a solid and yellowish white in colour. Bleaching powder can be easily identified by the strong smell of chlorine. When calcium hydroxide (slaked lime) reacts with chlorine, it gives calcium oxychloride (bleaching powder) and water is formed. Aqueous solution of bleaching powder is basic in nature. The material to be bleached is first passed through solution of NaOH to remove greasy matter. Then it is passed through aqueous solution of bleaching powder and very dil. HCI solution. HCI reacts with bleaching powder to liberate nascent oxygen which bleaches material.
(i) Bleaching powder is used as

(a) bleaching agent in textile, paper and jute industry

(b) disinfectant for water to make water free of germs

(c) oxidising agent in many industries

(d) all of these

(ii) Bleaching powder is also known as

(a) calcium oxychloride	(b) calcium hypochlorite
(c) chloride of lime	(d) all of these.

(iii) Bleaching powder gives smell of chlorine because it

(a) is unstable	(b) gives chlorine on exposure to atmosphere
(c) is a mixture of chlorine and slaked lime	(d) contains excess of chlorine

(iv) Select the correct statement(s) regarding bleaching powder.

(a) It is pale yellow powder having smell of chlorine

(b) It is sparingly soluble in water and gives milky suspension when dissolved in water

(c) As bleaching powder gives nascent oxygen, it shows bleaching property

(d) All of these

(v) Identify the product 'X' in the given reaction \(\mathrm{Ca}(\mathrm{OH})_{2}+\mathrm{Cl}_{2} \longrightarrow X+\mathrm{H}_{2} \mathrm{O}\)

(a) CaOCl₂

(b) CaCl₂

(c) Ca(CIO₃ )₂

(d) CaCO₃

3)

The preparation of washing soda is carried out through following steps:
Step-I: Manufacture of sodium hydrogen carbonate:\(\mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}+\mathrm{NH}_{3}+\mathrm{CO}_{2} \longrightarrow \ \mathrm{NaHCO}_{3}+ \ \mathrm{NH}_{4} \mathrm{Cl}\)
Sodium hydrogen carbonate
Step-II: Thermal decomposition of sodium hydrogen carbonate: When dry crystals of sodium hydrogen carbonate are heated strongly, they decompose to form anhydrous sodium carbonate (soda ash). \(2 \mathrm{NaHCO}_{3(s)} \longrightarrow \mathrm{Na}_{2} \mathrm{CO}_{3(s)}+\mathrm{CO}_{2(g)}+\mathrm{H}_{2} \mathrm{O}_{(g)}\)
Step-III: Recrystallisation of sodium carbonate: Sodium carbonate thus obtained is recrystallised to form crystals of washing soda.\(\mathrm{Na}_{2} \mathrm{CO}_{3(s)}+ 10 \mathrm{H}_{2} \mathrm{O}_{(l)} \longrightarrow \mathrm{Na}_{2} \mathrm{CO}_{3} \cdot 10 \mathrm{H}_{2} \mathrm{O}_{(s)}\)
Anhydrous Washing soda
sodium carbonate
(i) Some of the uses of washing soda are given below:
(I) It is used for removing permanent hardness of water
(II) It is used in glass industry
(III) It is used in paper industry
(IV) It is used in the manufacture of sodium compounds such as borax
Select the correct option regarding uses of washing soda

(a) (I) and (II) only	(b) (II) and (III) only
(c) (II) and (IV) only	(d) (I), (II), (III) and (IV)

(ii) What products will be formed along with water when sodium carbonate reacts with dilute hydrochloric acid?

(a) CO and NaCI	(b) Na and CO₂
(c) NaCI and CO₂	(d) Na and CO

(iii) Chief raw materials for the manufacture of washing soda are

(a) sodium chloride, ammonia and limestone

(b) ammonia, sodium hydrogen carbonate and copper sulphate

(c) sodium hydroxide, calcium chloride and ammonia

(d) calcium chloride, sodium chloride and copper sulphate.

(iv) What is the action of sodium carbonate on litmus paper?

(a) Turns red litmus blue

(b) Turns blue litmus red

(c) No change on litmus

(d) Both (a) and (b)

(v) What products will be obtained when solution of sodium carbonate and slaked lime is heated?

(a) NaOH and CaCl₂	(b) CaCO₃and NaOH
(c) NaHCO₃ and NaOH	(d) NaCI and CaCO₃

4)

"Indicator is a chemical compound which is added to the solution in very small amount to detect its acidic or basic nature:" As they show colour change in acidic and basic medium, they are also called acid-base indicators. In other words, "an acid-base indicator is that substance which possesses one colour in acidic medium and a different colour in alkaline medium:''
Indicators, basically, are coloured organic substances either extracted from plants (natural indicators) or synthesised in the laboratory (synthetic indicators). A few common acid base indicators are: Litmus, phenolphthalein, methyl orange etc. In addition to these there are some naturally occurring substances which have different smell in acidic and basic medium. These substances are called olfactory indicators.
(i) Which one of the following will turn red litmus blue?

(a) Vinegar

(b) Baking soda solution

(c) Lemon juice

(d) Soft drinks

(ii) A solution turns blue litmus red. The pH of the solution is probably

(a) 8

(b) 10

(c) 12

(d) 6

(iii) A solution in test tube 'A' turns red litmus blue, evolves hydrogen gas on reaction with zinc and does not react with sodium carbonate. Whereas, solution in test tube 'B' turns blue litmus red, liberates hydrogen gas on reaction with zinc and evolves carbon dioxide gas with sodium carbonate. Identify 'A' and 'B'

(a) 'A' is an acid, 'B' is a base	(b) 'A' is a base, 'B' is an acid
(c) Both 'A' and 'B' are bases	(d) Both 'A' and 'B' are acids

(iv) Select the incorrect option

Indicator	Colour in acidic medium	Colour in basic medium
(a) Litmus (Purple)	Red	Blue
(b) Flower of hydrangea plant (Blue)	Red	Green
(c) Red cabbage juice (Purple)	Red or Pink	Green
(d) Turmeric Juice (Yellow)	Yellow	Reddish brown

(v) Which one of the following can be used as an acid-base indicator by visually impaired student?

(a) Litmus

(b) Turmeric

(c) Vanilla essence

(d) Methyl orange

5)

Acids turn blue litmus red but have no effect on red litmus. Bases turn red litmus blue but have no effect on blue litmus. The sample in which phenolphthalein remains colourless while methyl orange changes to pink/ red are acids while the samples in which phenolphthalein colour changes to pink and methyl orange changes to yellow are bases. Some observations of different sample solutions in litmus, phenolphthalein and methyl orange indicator are given in the table.

Sample solution	Red litmus solution	Blue litmus solution	Phenolphthalein indicator	Methyl orange indicator
HCI	No colour change	Red	Colourless	Red/ Pink
H2 SO₄	No colour change	Red	Colourless	Red/ Pink
HNO₃	No colour change	Red	Colourless	Red/ Pink
CH₃COOH	No colour change	Red	Colourless	Red/ Pink
NaOH	Blue	No colour change	Pink	Yellow
Ca(OH)₂	Blue	No colour change	Pink	Yellow
KOH	Blue	No colour change	Pink	Yellow
Mg(OH)₂	Blue	No colour change	Pink	Yellow
NH₄OH	Blue	No colour change	Pink (Becomes colourless after sometime)	Yellow (Becomes colourless after sometime)

(i) Which of the following substances does not turn red litmus solution to blue?

(a) AI(OH)₃

(b) Mg(OH)₂

(c) H₃ PO₄

(d) NH₄OH

(ii) Phenolphthalein's colour in basic medium is ___________but in acid it is ___________ .

(a) pink, colourless

(b) yellow, pink

(c) pink, orange

(d) blue, red

(iii) Which of the following acids are edible?
(I) Citric acid
(II) Tartaric acid
(III) Hydrochloric acid
(IV) Carbonic acid.

(a) (I) and (II) only

(b) (1), (II) and (IV) only

(c) (I), (II) and (III) only

(d) (I), (II), (III) and (IV)

(iv) The colour of methyl orange in neutral solution is

(a) red

(b) orange

(c) yellow

(d) purple

(v) Which of the following cannot act as an indicator?

(a) Methyl orange

(b) Methyl chloride

(c) Turmeric juice

(d) Phenolphthalein

CBSE 10th Standard Science Subject Chemical Reactions and Equations Chapter Case Study Questions With Solution 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

Chemical equation is a method of representing a chemical reaction with the help of symbols and formulae of the substances involved in it. In a chemical equation, the substances which combine or react are called reactants and new substances produced are called products. A chemical equation is a short hand method of representing a chemical reaction. A balanced chemical equation has equal number of atoms of different elements in the reactants and products side. An unbalanced chemical equation has unequal number of atoms of one or more elements in reactants and products. Formulae of elements and compounds are not changed to balance an equation.
(i) Consider the following reaction:
pMg₃N₂ + qH₂O ⇾ rMg(OH)₂ + sNH₃
When the equation is balanced, the coefficients p, q, r, s respectively are

(a) 1,3,3,2	(b) 1,6,3,2
(c) 1,2,3,2	(d) 2,3,6, 2

(ii) Which of the following information is not conveyed by a balanced chemical equation?

(a) Physical states of reactants and products

(b) Symbols and formulae of all the substances involved in a particular reaction

(c) Number of atoms/molecules of the reactants and products formed

(d) Whether a particular reaction is actually feasible or not

(iii) The balancing of chemical equations is in accordance with

(a) law of combining volumes

(b) law of constant proportions

(c) law of conservation of mass

(d) both (b) and (c)

(iv) Which of the following chemical equations is an unbalanced one?

\( { (a) } 2 \mathrm{NaHCO}_{3} \longrightarrow \mathrm{Na}_{2} \mathrm{CO}_{3}+\mathrm{H}_{2} \mathrm{O}+\mathrm{CO}_{2}\)

\({ (b) } 2 \mathrm{C}_{4} \mathrm{H}_{10}+12 \mathrm{O}_{2} \longrightarrow 8 \mathrm{CO}_{2}+10 \mathrm{H}_{2} \mathrm{O}\)

\(\text {(c) } 2 \mathrm{Al}+6 \mathrm{H}_{2} \mathrm{O} \longrightarrow 2 \mathrm{Al}(\mathrm{OH})_{3}+3 \mathrm{H}_{2}\)

\(\text { (d) } 4 \mathrm{NH}_{3}+5 \mathrm{O}_{2} \longrightarrow 4 \mathrm{NO}+6 \mathrm{H}_{2} \mathrm{O}\)

(v) Which of the following statements is/are correct?

(a) A chemical equation tells us about the substances involved in a reaction.

(b) A chemical equation informs us about the symbols and formulae of the substances involved in a reaction.

(c) A chemical equation tells us about the atoms or molecules of the reactants and products involved in a reaction.

(d) All the above

2)

In decomposition reactions, a single reactant breaks down to form two or more products. A decomposition reaction is opposite to combination reaction. Thermal decomposition reactions use the energy in form of heat for the decomposition of reactants. Electrolytic decomposition reactions involve the use of electrical energy for the decomposition of reactant molecules. Photolysis or photochemical decomposition involves the use of light energy for the purpose of decomposition.
(i) Which of the following reactions is a decomposition reaction?

\({ (a) \ } \mathrm{NaOH}+\mathrm{HCl} \longrightarrow \mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}\)	\({ (b) \ } \mathrm{NH}_{4} \mathrm{CNO} \longrightarrow \mathrm{H}_{2} \mathrm{NCONH}_{2}\)
\({ (C) \ } 2 \mathrm{KCIO}_{3} \longrightarrow 2 \mathrm{KCl}+3 \mathrm{O}_{2}\)	\( { (d) \ } \mathrm{H}_{2}+\mathrm{I}_{2} \longrightarrow 2 \mathrm{HI}\)

\({ (ii) \ } 2 \mathrm{~Pb}\left(\mathrm{NO}_{3}\right)_{2} \longrightarrow 2 \mathrm{PbO}+n A+\mathrm{O}_{2}\)
What is nA in the given reaction?

(a) 4NO

(b) 4NO₂

(c) 2PbNO₂

(d) NO₂

(iii) Amino acid is formed by the decomposition of which component of our diet?

(a) Carbohydrate

(b) Starch

(c) Protein

(d) Fat

(iv) Silver chloride on exposure to sunlight for a long duration turns grey due to
(I) the formation of silver by decomposition of silver chloride
(II) sublimation of silver chloride
(III) decomposition of chlorine gas from silver chloride
(IV) oxidation of silver chloride
The correct statement(s) is/are

(a) Only (I)

(b) Only (II) and (III)

(c) Only (I) and (II)

d) Only (IV)

(v) What type of chemical reaction takes place when electricity is passed through water?

(a) Thermal decomposition	(b) Electrolytic decomposition
(c) Photochemical decomposition	(d) Displacement reaction

3)

Redox reactions are those reactions in which oxidation and reduction occur Simultaneously. A redox reaction is made up of two half reactions. In the first half reaction, oxidation takes place and in second half reaction, reduction occurs. Oxidation is a process in which a substance loses electrons and in reduction, a substance gains electrons. The substance which gains electrons is reduced and acts as an oxidising agent. On the other hand, a substance which loses electrons is oxidised and acts as a reducing agent.
(i) Which of the following is a redox reaction?

\({ (a) \ } \mathrm{CaCO}_{3} \rightarrow \mathrm{CaO}+\mathrm{CO}_{2}\)	\(\text { (b) } \mathrm{H}_{2}+\mathrm{Cl}_{2} \rightarrow 2 \mathrm{HCl}\)
\({ (c) \ } \mathrm{CaO}+2 \mathrm{HCl} \rightarrow \mathrm{CaCl}_{2}+\mathrm{H}_{2} \mathrm{O}\)	\(\text { (d) } \mathrm{NaOH}+\mathrm{HCl} \rightarrow \mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}\)

(ii) Identify the reaction in which H2 02 is acting as a reducing agent.

\(\text { (a) } \mathrm{H}_{2} \mathrm{SO}_{3}+\mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow \mathrm{H}_{2} \mathrm{SO}_{4}+\mathrm{H}_{2} \mathrm{O}\)	\(\text { (b) } 2 \mathrm{Hl}+\mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}+\mathrm{I}_{2}\)
\(\text { (c) } \mathrm{Cl}_{2}+\mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow 2 \mathrm{HCl}+\mathrm{O}_{2}\)	\(\text { (d) } 2 \mathrm{FeCl}_{2}+2 \mathrm{HCl}+\mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow 2 \mathrm{FeCl}_{3}+2 \mathrm{H}_{2} \mathrm{O}\)

(iii) For the following reactions, identify the one in which H₂S acts as a reducing agent.

\(\text { (a) } \mathrm{CuSO}_{4}+\mathrm{H}_{2} \mathrm{~S} \longrightarrow \mathrm{CuS}+\mathrm{H}_{2} \mathrm{SO}_{4}\)	\(\text { (b) } \mathrm{Cd}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{H}_{2} \mathrm{~S} \longrightarrow \mathrm{CdS}+2 \mathrm{HNO}_{3}\)
\(\text { (c) } 2 \mathrm{FeCl}_{3}+\mathrm{H}_{2} \mathrm{~S} \longrightarrow 2 \mathrm{FeCl}_{2}+2 \mathrm{HCl}+\mathrm{S}\)	(d) None of these

(iv) For the following reaction, identify the correct statement.
\(\mathrm{ZnO}+\mathrm{CO} \longrightarrow \mathrm{Zn}+\mathrm{CO}_{2}\)

(a) ZnO is being reduced.	(b) CO₂ is being oxidised
(c) CO is being reduced.	(d) ZnO is being oxidised.

(v) In the following reaction, which substance is reduced?
\(\mathrm{PbS}+4 \mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow \mathrm{PbSO}_{4}+4 \mathrm{H}_{2} \mathrm{O}\)

(a) H₂O

(b) H₂ O₂

(c) PbS

d) PbSO₄

4)
In a balanced chemical reaction, equal number of atoms are present on both sides of reaction. A balanced chemical reaction is based on law of conservation of mass which means that total mass of reactants and products participating in a reaction must be equal. For example, a balanced chemical equation of burning of magnesium in oxygen to form magnesium oxide is written as :
\(2 \mathrm{Mg}+\mathrm{O}_{2} \longrightarrow 2 \mathrm{MgO}\)
The mass of reactants (2 x 24 + 32 = 80) is equal to the mass of products [2 x (24 + 16) = 80]
(i) In a reaction, 35 g of reactant, PQ breaks down into 20 g of product, P and an unknown amount of product, Q. Using the law of conservation of mass, weight of products, Q will be

(a) 25g (b) 35g (c) 30g (d) 15g

(ii) When solid mercury (II) oxide is heated, liquid mercury and oxygen gas are produced. Which of the following statements is true regarding the balanced chemical equation for this process?
(a) 1 mole of mercury (II) oxide produces two moles of mercury and one mole of oxygen gas
(b) 2 moles of mercury (II) oxide produce one mole of mercury and one mole of oxygen gas
(c) 1 mole of mercury (II) oxide produces half mole of mercury and half mole of oxygen gas
(d) 2 moles of mercury (II) oxide produce 2 moles of mercury and one mole of oxygen gas
(iii) Which of the following laws is satisfied by a balanced chemical equation?

(a) Law of multiple proportions (b) Law of conservation of mass

(c) Law of conservation of motion (d) Law of conservation of magnetism

(iv) In the given chemical reaction
\(\mathrm{C}_{6} \mathrm{H}_{6(l)}+15 \mathrm{O}_{2(g)} \longrightarrow m \mathrm{CO}_{2(g)}+n \mathrm{H}_{2} \mathrm{O}_{(l)}\)
The values of m and n are respectively

(a) 14 and 8 (b) 12 and 6 (c) 8 and 10 (d) 12 and 10

(v) Sulphur dioxide reacts with oxygen to form sulphur trioxide. What would be the molar ratio of sulphur dioxide to sulphur trioxide?

(a) 2: 3 (b) 1: 1 (c) 1: 2 (d) 3: 2

5)

In a chemical reaction, reactants are converted into products. The conversion of reactants into products in a chemical reaction is often accompanied by some features which can be observed easily. These easily observed features which take place as a result of chemical reaction are known as characteristics of chemicals reactions. Some important characteristics of chemical reactions are:
(I) Evolution of heat
(II) Formation of precipitate
(III) Change in colour
(IV) Change in temperature
(V) Change in state
Anyone of these general characteristics can tell us whether a chemical reaction has taken place or not.
(i) Reaction of magnesium with air is a/an

(a) exothermic reaction	(b) endothermic reaction
(c) reversible reaction	(d) substitution reaction

(ii) In the following reaction
\(\mathrm{Ca}_{(a q)}^{2+}+2 \mathrm{OH}_{(a q)}^{-} \longrightarrow \mathrm{Ca}(\mathrm{OH})_{2(s)}\)
precipitate of calcium hydroxide will be of

(a) green colour

(b) blue colour

(c) brown colour

(d) white colour

(iii) In the given reaction,
\(\mathrm{S}_{(s)}+\mathrm{O}_{2(g)} \longrightarrow \mathrm{SO}_{2}\)
the physical state of SO₂ is

(a) liquid

(b) solid

(c) gaseous

(d) all three

(iv) Which one of the following processes involve chemical reactions?

(a) Storing of oxygen gas under pressure in a gas cylinder.

(b) Keeping petrol in a china dish in the open.

(c) Liquefaction of air.

(d) Heating copper wire in the presence of air at high temperature.

(v) In which of the following reactions, high amount of heat energy will be evolved?

(a) Electrolysis of water	(b) Dissolution of NH4Cl in water
(c) Burning of L.P.G.	(d) Decomposition of AgBr in the presence of light

CBSE 10th Standard Science Subject Chemical Reactions and Equations Chapter Case Study Questions 2021 - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

A reaction in which two or more reactants combine to form a single product is called a combination reaction. For example, calcium oxide reacts vigorously with water to form calcium hydroxide. The reaction is highly exothermic in nature, as lots of heat is produced during the reaction.
\(\mathrm{CaO}_{(s)}+\mathrm{H}_{2} \mathrm{O}_{(l)} \longrightarrow \mathrm{Ca}(\mathrm{OH})_{2(a q)}+\text { Heat }\)
Calcium oxide Water Calcium hydroxide
Solution of Ca(OH)₂ is used for white wash the walls. Calcium hydroxide reacts slowly with carbon dioxide in air to form a thin layer of calcium carbonate on the wall which gives a shiny appearance to wall. Calcium carbonate will form after two or three days of white wash.
(i) What is the chemical name of quick lime?

(a) Calcium oxide

(b) Calcium carbonate

(c) Calcium hydroxide

(d) Carbon dioxide

(ii) When carbon dioxide is passed through lime water,

(a) calcium hydroxide is formed	(b) white precipitate of CaO is formed
(c) lime water turns milky	(d) colour of lime water becomes green.

(iii) Following observations are observed when calcium oxide reacts vigorously with water.

Identify the incorrect observations
(I) It is an endothermic reaction (II) Slaked lime is produced.
(III) Quick lime is produced. (IV) It is an exothermic reaction.
(V) It is a combination reaction

(a) (I) and (II)

(b) (III) and (IV)

(c) (I) and (III)

(d) (II), (IV) and (V)

(iv) Quick lime combines Vigorously with water to form (A) which reacts slowly with the carbon dioxide in air to form (B)
Identify the compounds(A) and (B)

(A)	(B)
(a) Calcium carbonate	Calcium hydroxide
(b) Calcium hydroxide	Calcium carbonate
(c) Calcium	Calcium bicarbonate
(d) Calcium bicarbonate	Calcium

(v) Among the following, the endothermic reaction is

(a) combination of carbon and oxygen to form carbon monoxide

(b) combination of nitrogen and oxygen to form nitrogen monoxide

(c) combination of glucose and oxygen to form carbon dioxide and water

(d) combination of zinc and hydrochloric acid to form zinc chloride and hydrogen

2)

Reactions in which one element takes place of another element in a compound, are known as displacement reactions. In general, more reactive elements displaces a less reactive element from its compound. In all single displacement reactions, only one element displaces another element from its compound. The single displacement reactions are, however, written as just displacement reactions. The displacement reaction between iron (III) oxide and powdered aluminium produces so much heat that iron metal obtained is in molten form.
(i) Copper displaces which of the following metals from its salt solution?

(a) ZnSO₄

(b) FeSO₄

(c) AgNO₃

(d) NiSO₄

(ii) When zinc reacts with dilute sulphuric acid, the gas evolved is

(a) red in colour and have a sweet smelling

(b) green in colour and have a foul smell

(c) colourless, odourless and burns with a pop sound

(d) colourless, pungent smelling and burns with a pop sound

(iii) When dry hydrogen is passed over a heated oxide of metal X using the apparatus shown below, a reddishbrown residue is obtained

The reddish -brown residue could be

(a) copper

(b) lead

(c) silver

(d) zinc

(iv) Which of the following reactions is a displacement reaction?

\(\text { (a) } \mathrm{CaO}+\mathrm{H}_{2} \mathrm{O} \longrightarrow \mathrm{Ca}(\mathrm{OH})_{2}\)	\(\text { (b) } \mathrm{MgCO}_{3} \longrightarrow \mathrm{Mg}+\mathrm{CO}_{2}\)
\(\text { (c) } \mathrm{Mg}+\mathrm{CuSO}_{4} \longrightarrow \mathrm{MgSO}_{4}+\mathrm{Cu}\)	\(\text { (d) } \mathrm{H}_{2}+\mathrm{Cl}_{2} \longrightarrow 2 \mathrm{HCl}\)

(v) When dilute hydrochloric acid is added to granulated zinc placed in a test tube, the observation made is

(a) the surface of the metal turns shining

(b) the reaction mixture turns milky

(c) greenish yellow gas is evolved

(d) the colourless and odourless gas evolves with a pop sound.

3)

Those reactions in which two compounds react by an exchange of ions to form two new compounds are called double displacement reactions. A double displacement reaction usually occurs in solution and one of the products, being insoluble, precipitate out (separates as a solid). Any reaction in which an insoluble solid (called precipitate) is formed that separates from the solution is called a precipitation reaction. The reaction in which acid or acidic oxide reacts with base or basic oxide to form salt and water is called neutralisation reaction.
For example, \(2 \mathrm{NaOH}+\mathrm{H}_{2} \mathrm{SO}_{4} \longrightarrow \mathrm{Na}_{2} \mathrm{SO}_{4}+\mathrm{H}_{2} \mathrm{O}\)
(i) When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphide is obtained and the sulphuric acid so formed remains in the solution. The reaction is an example of a

(a) combination reaction	(b) displacement reaction
(c) decomposition reaction	(d) double displacement reaction

(ii) Which of the following is not a double displacement reaction?

\(\text { (a) } \mathrm{AgNO}_{3(a q)}+\mathrm{NaCl}_{(a q)} \longrightarrow \mathrm{AgCl}_{(s)}+\mathrm{NaNO}_{3(a q)}\)	\(\text { (b) } \mathrm{Zn}_{(s)}+\mathrm{H}_{2} \mathrm{SO}_{4(a q)} \longrightarrow \mathrm{ZnSO}_{4(a q)}+\mathrm{H}_{2(g)}\)
\(\text { (c) } \mathrm{CuSO}_{4(a q)}+\mathrm{H}_{2} \mathrm{~S}_{(a q)} \longrightarrow \mathrm{CuS}_{(s)}+\mathrm{H}_{2} \mathrm{SO}_{4(a q)}\)	\(\text { (d) } \mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2(a q)}+2 \mathrm{KI}_{(a q)} \longrightarrow \mathrm{PbI}_{2(s)}+2 \mathrm{KNO}_{3(a q)}\)

(iii) Barium chloride on reaction with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved?
(I) Displacement reaction
(II) Precipitation reaction
(III) Combination reaction
(IV) Double displacement reaction

(a) (I) only

(b) (II) only

(c) (III) and (IV) only

(d) (II) and ( V) only

(iv) Identify A in the following reaction.
\(\mathrm{AlCl}_{3(a q)}+3 \mathrm{NH}_{4} \mathrm{OH}_{(a q)} \longrightarrow A+3 \mathrm{NH}_{4} \mathrm{Cl}_{(a q)}\)

(a) AI(OH)₃

(b) Al₂O₃

(c) AIH₃

(d) AIN

(v) Consider the following reaction,
\(\mathrm{BaCl}_{2}+\mathrm{Na}_{2} \mathrm{SO}_{4} \longrightarrow \mathrm{BaSO}_{4}+2 \mathrm{NaCl}\)
identify the precipitate in the reaction,

(a) BaCl₂

(b) BaSO₄

(c) Na2sO₄

(d) NaCI

4)

The earlier concept of oxidation and reduction is based on the addition or removal of oxygen or hydrogen elements so, in terms of oxygen and hydrogen, oxidation is addition of oxygen to a substance and removal of hydrogen from a substance. On the other hand, reduction is addition of hydrogen to a substance and removal of oxygen from a substance. The substance which gives oxygen to another substance or removes hydrogen from another substance in an oxidation reaction is known as oxidising agent, while the substance which gives hydrogen to another substance or removes oxygen from another substance in a reduction reaction is known as reducing agent. For example,

(i) A redox reaction is one in which

(a) both the substances are reduced

(b) both the substances are oxidised

(c) an acid is neutralised by the base

(d) one substance is oxidised while the other is reduced.

(ii) In the reaction, \(\mathrm{H}_{2} \mathrm{~S}+\mathrm{Cl}_{2} \longrightarrow \mathrm{S}+2 \mathrm{HCl}\)

(a) H₂S is the reducing agent.	(b) HCI is the oxidising agent.
(c) H₂S is the oxidising agent.	(d) Cl₂is the reducing agent.

(iii) Which ofthe following processes does not involve either oxidation or reduction?

(a) Formation of slaked lime from quick lime.

(b) Heating mercuric oxide.

(c) Formation of manganese chloride from manganese oxide (MnO₂).

(d) Formation of zinc from zinc blende.

\(\text { (iv) } \mathrm{Mg}+\mathrm{CuO} \longrightarrow \mathrm{MgO}+\mathrm{Cu}\)

Which of the following is wrong relating to the above reaction?

(a) CuO gets reduced

(b) Mg gets oxidised.

(c) CuO gets oxidised.

(d) It is a redox reaction.

(v) Identify the correct oxidising agent and reducing agent in the following reaction.
\(\mathrm{Fe}_{2} \mathrm{O}_{3}+2 \mathrm{Al} \longrightarrow 2 \mathrm{Fe}+\mathrm{Al}_{2} \mathrm{O}_{3}\)

(a) AI- Oxidising agent, Fe₂O_{3 -} Reducing agent	(b) Fe_{2 O3} - Oxidising agent, AI- Reducing agent
(c) Fe - Oxidising agent, Al₂O₃- Reducing agent	(d) Fe_2O3- Oxidising agent, Al₂O₃ - Reducing agent

5)
Oxidation has damaging effect on metals as well as on food. The damaging effect of oxidation on metal is studied as corrosion and that on food is studied as rancidity. The phenomenon due to which metals are slowly eaten away by the reaction of air, water and chemicals present in atmosphere, is called corrosion. For example, iron articles are shiny when new, but get coated with a reddish brown powder when left for sometime. This process is known as rusting of iron. Rancidity is the process of slow oxidation of oil and fat (which are volatile in nature) present in the food materials resulting in the change of smell and taste in them.
(i) Rancidity can be prevented by

(a) adding antioxidants (b) packaging oily food in nitrogen gas

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

(ii) Combination of phosphorus and oxygen is an example of

(a) oxidation (b) reduction (c) rancidity (d) none of these

(iii) A science teacher wrote the following statements about rancidity :
(I) When fats and oils are reduced, they become rancid.
(II) In chips packet, rancidity is prevented by oxygen.
(III) Rancidity is prevented by adding antioxidants.
Select the correct option.

(a) (I) only (b) (II) and (III) only (c) (III) only (d) (I), (II), and (III)

(iv) Two statements are given below regarding rusting of iron.
(I) The rusting of iron is a redox reaction and reaction occurs as, \(4 \mathrm{Fe}+3 \mathrm{O}_{2} \longrightarrow 4 \mathrm{Fe}^{3+}+6 \mathrm{O}^{2-}\)
(II) The metallic iron is oxidised to \(\mathrm{Fe}^{2+} \text { and } \mathrm{O}_{2} \text { is reduced to } \mathrm{O}^{2-}\)
Select the correct statement(s).

(a) I only (b) II only (c) Both I and II (d) None of these

(v) Which of the following measures can be adopted to prevent or slow down rancidity?
(I) Food materials should be packed in air tight container.
(II) Food should be refrigerated.
(III) Food materials and cooked food should be kept away from direct sunlight

(a) Only II and III (b) Only I and III (c) Only II and III (d) I, II and III

CBSE 10th Standard Science Subject Case Study Questions - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

Redox reactions are those reactions in which oxidation and reduction occur Simultaneously. A redox reaction is made up of two half reactions. In the first half reaction, oxidation takes place and in second half reaction, reduction occurs. Oxidation is a process in which a substance loses electrons and in reduction, a substance gains electrons. The substance which gains electrons is reduced and acts as an oxidising agent. On the other hand, a substance which loses electrons is oxidised and acts as a reducing agent.
(i) Which of the following is a redox reaction?

\({ (a) \ } \mathrm{CaCO}_{3} \rightarrow \mathrm{CaO}+\mathrm{CO}_{2}\)	\(\text { (b) } \mathrm{H}_{2}+\mathrm{Cl}_{2} \rightarrow 2 \mathrm{HCl}\)
\({ (c) \ } \mathrm{CaO}+2 \mathrm{HCl} \rightarrow \mathrm{CaCl}_{2}+\mathrm{H}_{2} \mathrm{O}\)	\(\text { (d) } \mathrm{NaOH}+\mathrm{HCl} \rightarrow \mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}\)

(ii) Identify the reaction in which H2 02 is acting as a reducing agent.

\(\text { (a) } \mathrm{H}_{2} \mathrm{SO}_{3}+\mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow \mathrm{H}_{2} \mathrm{SO}_{4}+\mathrm{H}_{2} \mathrm{O}\)	\(\text { (b) } 2 \mathrm{Hl}+\mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow 2 \mathrm{H}_{2} \mathrm{O}+\mathrm{I}_{2}\)
\(\text { (c) } \mathrm{Cl}_{2}+\mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow 2 \mathrm{HCl}+\mathrm{O}_{2}\)	\(\text { (d) } 2 \mathrm{FeCl}_{2}+2 \mathrm{HCl}+\mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow 2 \mathrm{FeCl}_{3}+2 \mathrm{H}_{2} \mathrm{O}\)

(iii) For the following reactions, identify the one in which H₂S acts as a reducing agent.

\(\text { (a) } \mathrm{CuSO}_{4}+\mathrm{H}_{2} \mathrm{~S} \longrightarrow \mathrm{CuS}+\mathrm{H}_{2} \mathrm{SO}_{4}\)	\(\text { (b) } \mathrm{Cd}\left(\mathrm{NO}_{3}\right)_{2}+\mathrm{H}_{2} \mathrm{~S} \longrightarrow \mathrm{CdS}+2 \mathrm{HNO}_{3}\)
\(\text { (c) } 2 \mathrm{FeCl}_{3}+\mathrm{H}_{2} \mathrm{~S} \longrightarrow 2 \mathrm{FeCl}_{2}+2 \mathrm{HCl}+\mathrm{S}\)	(d) None of these

(iv) For the following reaction, identify the correct statement.
\(\mathrm{ZnO}+\mathrm{CO} \longrightarrow \mathrm{Zn}+\mathrm{CO}_{2}\)

(a) ZnO is being reduced.	(b) CO₂ is being oxidised
(c) CO is being reduced.	(d) ZnO is being oxidised.

(v) In the following reaction, which substance is reduced?
\(\mathrm{PbS}+4 \mathrm{H}_{2} \mathrm{O}_{2} \longrightarrow \mathrm{PbSO}_{4}+4 \mathrm{H}_{2} \mathrm{O}\)

(a) H₂O

(b) H₂ O₂

(c) PbS

d) PbSO₄

2)

The acidic behaviour of acids is due to the presence of hydrogenil(H⁺)ions in them. They produce hydrogen ions in the presence of water. Water is a polar solvent and this property of water helps in weakening the bond between the ions and makes them soluble. Hence, acids and bases produce ions in aqueous solutions.
It may be noted that a dry Hel gas or a solution of hydrogen chloride in organic, nonpolar solvents like toluene or benzene do not show acidic properties. This is because hydrogen chloride does not undergo ionization in toluene.
The reason why Hel splits into H⁺and CI^-ions in presence of water lies in the fact that water molecules, being polar, pull the H⁺and Cl^-ions apart and thus, the bond in Hel is broken

(i) Identify the wrong statement.

(a) Higher the hydronium ion concentration, lower is the pH value

(b) Universal indicator is used to judge how strong a given acid or base is

(c) As the pH value increases from 7 to 14, it represents increase in H⁺ ion concentration in the solution

(d) Value less than 7 on the pH scale represents an acidic solution

(ii) If the pH of a solution is 8, then its [H⁺] ion is

(a) log 10^{- 8}

(b) 10⁸

(c) 10^{- 8}

(d) 8

(iii) In terms of acidic strength, which one of the following is in the correct increasing order?

(a) Water < Acetic acid < Hydrochloric acid	(b) Water < Hydrochloric acid < Acetic acid
(c) Acetic acid < Water < Hydrochloric acid	(d) Hydrochloric acid < Water < Acetic acid

(iv) Which of the following compounds does not give H⁺ ions in aqueous solution?

(a) H₃PO₄

(b) C₂H₅OH

(c) H₂CO₃

(d) CH₃COOH

(v) Four solutions labelled as P, Q, Rand Shave pH values 1, 9, 3 and 13 respectively.
Which of the following statements about the given solutions is incorrect?

(a) Solution P has higher concentration of hydrogen ions than solution R.

(b) Solution Q has lower concentration of hydroxide ions than solution S.

(c) Solutions P and Q will turn red litmus solution blue.

(d) Solution P is highly acidic while solution Q is weakly basic.

3)

Baking powder produces carbon dioxide on heating, so it is used in cooking to make the batter spongy. Although, baking soda also produces CO₂on heating, but it is not used in cooking because on heating, baking soda produces sodium carbonate along with carbon dioxide. Sodium carbonate, thus, produced, makes the taste bitter. Baking powder is the mixture of baking soda and a mild edible acid. Generally, tartaric acid is mixed with baking soda to make baking powder. When baking powder is heated, NaHCO₃ decomposes to give CO₂ which makes bread and cake fluffy. Tartaric acid helps to remove bitter taste due to formation of sodium tartrate.
\(2 \mathrm{NaHCO}_{3}+ \ \ \mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{6} \quad \longrightarrow \quad 2 \mathrm{CO}_{2}+2 \mathrm{H}_{2} \mathrm{O}+\mathrm{Na}_{2} \mathrm{C}_{4} \mathrm{H}_{4} \mathrm{O}_{6}\)
Baking soda Tartaric acid Carbon dioxide Sodium tartrate
(i) On passing excess CO₂ gas in aqueous solution of sodium carbonate, the substance obtained is

(a) NaOH	(b) NaHCO₃
(c) Na₂CO₃·10H₂O	(d) Na2CO₃ ·H₂O

(ii) When sodium hydrogen carbonate is added to acetic acid, it evolves a gas. Which of the following statements are true about the gas evolved?
(I) It turns lime water milky
(II) It extinguishes a burning splinter
(III) It dissolves in a solution of sodium hydroxide
(IV) It has a pungent odour

(a) (I) and (II)	(b) (I), (II) and (III)
(c) (II), (III) and (IV)	(d) (I) and (IV)

(iii) Select the correct statement regarding sodium hydrogen carbonate.

(a) CO and CO₂ are produced during the heating ofNaHCO₃

(b) It is insoluble in water.

(c) It is used in soda-acid fire extinguishers.

(d) All of these

(iv) Acetic acid was added to a solid X kept in a test tube. A colourless and odourless gas was evolved. The gas was passed through lime water which turned milky. It was concluded that

(a) solid X is sodium hydroxide and the gas evolved is CO₂

(b) solid X is sodium bicarbonate and the gas evolved is CO₂

(c) solid X is sodium acetate and the gas evolved is CO₂

(d) solid X is sodium chloride and the gas evolved is CO₂

(v) Which of the following statements are correct regarding baking soda?
(I) Baking soda is sodium hydrogen carbonate
(II) On heating, baking soda gives sodium carbonate
(III) It is used for manufacture of soap
(IV) It is an ingredient of baking powder

(a) I and IV only	(b) I, II and III only
(c) I, II and IV only	(d) I, II, III and I

4)
The chemical reactivity of an element depends upon its electronic configuration. All elements having less than eight electrons in the outermost shell show chemical reactivity. During chemical reactions, atoms of all elements tend to achieve a completely filled valence shell. Metals are electropositive in nature. They have tendency to lose one or more electrons present in the valence shell of their atoms to form cations and achieve nearest noble gas configuration. The compounds formed by the transfer of electrons from one element to other are known as ionic or electrovalent compounds.
(i) The electronic configurations of three elements X, Y and Z are:
X : 2 Y: 2, 8, 7 Z : 2, 8, 2
Which of the following is correct regarding these elements?

(a) X is a metal. (b) Y is a metal.

(c) Z is a non-metal (d)Yis a non-metal and Z is a metal

(ii) Element X reacts with element Y to form a compound Z. During the formation of compound Z, atoms of X lose one electron each whereas atoms of Y gain one electron each. Which of the following properties is not shown by compound Z?

(a) High melting point

(b) Low melting point

(c) Occurrence as solid

(d) Conduction of electricity in molten state

(iii) Which of the following is correct representation of formation of magnesium chloride?

(d) None of these

(iv) The electronic configuration of sodium ion is

(a) 2,8,8 (b) 2,8,2. (c) 2,6 (d) 2,8.

(v)Which of the following represents an electropositive element?

(a) 2,8,6 (b) 2,8,8 (c) 2,8,8,1 (d) 2, 7
5)
A hydrocarbon (P) has the molecular formula C₁₀H₂₂.A hydrocarbon (Q) has two carbon atoms less than (P) and belong to the same homologous series. A hydrocarbon (R) has two carbon atoms more than (P) and belong to the same homologous series.
(i) What is the molecular formula of (Q)?

(a) C₁₂H₂₆ (b) C₈H₁₆ (c) C₈H₁₈ (d) C₈H₁₄

(ii) To which homologous series do the compound (P), (Q) and (R) belong?

(a) C_nH_2n (b) C₂H_{2n- 2} (c) C_nH_2n+2 (d) C_nH_{2n + 1}

(iii) What is the molecular formula of (R)?

(a) C₁₂H₂₆ (b) C₁₂H₂₄ (c) C₁₂H₂₂ (d) C_l2H₂₈

(iv) Identify the correct statement about compounds (P), (Q) and (R).

(a) They have same melting and boiling points. (b) They have same chemical properties.

(c) They have different general formula. (d) They differ by -CH₂ unit.

(v) Compounds (P), (Q) and (R) are

(a) alkanes (b) alkenes (c) alkynes (d) none of these.

CBSE 10th Standard Science Subject Case Study Questions with Solutions 2021 Part - II - by Prerna - Bangalore - May 21, 2021 - View & Read

1)
In a balanced chemical reaction, equal number of atoms are present on both sides of reaction. A balanced chemical reaction is based on law of conservation of mass which means that total mass of reactants and products participating in a reaction must be equal. For example, a balanced chemical equation of burning of magnesium in oxygen to form magnesium oxide is written as :
\(2 \mathrm{Mg}+\mathrm{O}_{2} \longrightarrow 2 \mathrm{MgO}\)
The mass of reactants (2 x 24 + 32 = 80) is equal to the mass of products [2 x (24 + 16) = 80]
(i) In a reaction, 35 g of reactant, PQ breaks down into 20 g of product, P and an unknown amount of product, Q. Using the law of conservation of mass, weight of products, Q will be

(a) 25g (b) 35g (c) 30g (d) 15g

(ii) When solid mercury (II) oxide is heated, liquid mercury and oxygen gas are produced. Which of the following statements is true regarding the balanced chemical equation for this process?
(a) 1 mole of mercury (II) oxide produces two moles of mercury and one mole of oxygen gas
(b) 2 moles of mercury (II) oxide produce one mole of mercury and one mole of oxygen gas
(c) 1 mole of mercury (II) oxide produces half mole of mercury and half mole of oxygen gas
(d) 2 moles of mercury (II) oxide produce 2 moles of mercury and one mole of oxygen gas
(iii) Which of the following laws is satisfied by a balanced chemical equation?

(a) Law of multiple proportions (b) Law of conservation of mass

(c) Law of conservation of motion (d) Law of conservation of magnetism

(iv) In the given chemical reaction
\(\mathrm{C}_{6} \mathrm{H}_{6(l)}+15 \mathrm{O}_{2(g)} \longrightarrow m \mathrm{CO}_{2(g)}+n \mathrm{H}_{2} \mathrm{O}_{(l)}\)
The values of m and n are respectively

(a) 14 and 8 (b) 12 and 6 (c) 8 and 10 (d) 12 and 10

(v) Sulphur dioxide reacts with oxygen to form sulphur trioxide. What would be the molar ratio of sulphur dioxide to sulphur trioxide?

(a) 2: 3 (b) 1: 1 (c) 1: 2 (d) 3: 2

2)

Sodium chloride obtained from sea water or from lakes contains many impurities such as sulphates of sodium and magnesium along with chlorides of calcium and magnesium. The chlorides of calcium and magnesium are particularly undesirable on account of their deliquescent nature.
For its purification, common salt is dissolved in minimum quantity of water to get a saturated solution from which insoluble impurities are filtered off. Then hydrogen chloride gas is passed through the saturated solution and the crystals of pure NaCl separate out. The soluble impurities remain in the mother liquor. The crystals are filtered, washed and dried.
(i) Select the correct statement regarding salt NaCl.

(a) Pure NaCI is hygroscopic in nature

(b) It is soluble in alcohol

(c) Pure NaCI is not hygroscopic, it shows hygroscopic nature due to impurities

(d) It is a brown crystalline solid

(ii) Nature of aqueous solution of common salt is

(a) acidic

(b) alkaline

(c) basic

(d) neutral

(iii) In the given series of reactions, Y and Z respectively are
²

(a) NaHCO₃ , NaOCl₂

(b) NH₄CI, Na2CO₃

(c) Na₂CO₃, NH₄CI

(d) Na₂CO₃, NaHCO₃

(iv) Which of the following compounds is alkaline in aqueous medium?

(a) Na₂CO₃

(b) NaCI

(c) H₂CO₃

(d) CuSO₄

(v) Some statements regarding salt NaCI are given below
(I) It is prepared by chlor-alkali process
(II) It is a white crystalline substance
(III) It also exists in the form of rocks and is called rock salt
(IV) It is a neutral salt, pH value of NaCI is 7

(a) II and III only

(b) III and IV only

(c) I and IV only

(d) II, III and IV only

3)

Acids turn blue litmus red but have no effect on red litmus. Bases turn red litmus blue but have no effect on blue litmus. The sample in which phenolphthalein remains colourless while methyl orange changes to pink/ red are acids while the samples in which phenolphthalein colour changes to pink and methyl orange changes to yellow are bases. Some observations of different sample solutions in litmus, phenolphthalein and methyl orange indicator are given in the table.

Sample solution	Red litmus solution	Blue litmus solution	Phenolphthalein indicator	Methyl orange indicator
HCI	No colour change	Red	Colourless	Red/ Pink
H2 SO₄	No colour change	Red	Colourless	Red/ Pink
HNO₃	No colour change	Red	Colourless	Red/ Pink
CH₃COOH	No colour change	Red	Colourless	Red/ Pink
NaOH	Blue	No colour change	Pink	Yellow
Ca(OH)₂	Blue	No colour change	Pink	Yellow
KOH	Blue	No colour change	Pink	Yellow
Mg(OH)₂	Blue	No colour change	Pink	Yellow
NH₄OH	Blue	No colour change	Pink (Becomes colourless after sometime)	Yellow (Becomes colourless after sometime)

(i) Which of the following substances does not turn red litmus solution to blue?

(a) AI(OH)₃

(b) Mg(OH)₂

(c) H₃ PO₄

(d) NH₄OH

(ii) Phenolphthalein's colour in basic medium is ___________but in acid it is ___________ .

(a) pink, colourless

(b) yellow, pink

(c) pink, orange

(d) blue, red

(iii) Which of the following acids are edible?
(I) Citric acid
(II) Tartaric acid
(III) Hydrochloric acid
(IV) Carbonic acid.

(a) (I) and (II) only

(b) (1), (II) and (IV) only

(c) (I), (II) and (III) only

(d) (I), (II), (III) and (IV)

(iv) The colour of methyl orange in neutral solution is

(a) red

(b) orange

(c) yellow

(d) purple

(v) Which of the following cannot act as an indicator?

(a) Methyl orange

(b) Methyl chloride

(c) Turmeric juice

(d) Phenolphthalein

4)

Although there is no sharp line of distinction between metals and non-metals yet there are some distinctive differences. The main points of differences are:

Property	Metals	Non-metals
Electronic structure	They have 1 to 3 electrons in the outermost shell of their atoms	They have 4 to 8 electrons in the outermost shell of their atoms.
State of existence	They are mostly solid at room temperature except mercury and gallium which are liquid.	They are either solids or gases at room temperature (except bromine which is a liquid).
Density	They have high density.	They have low density.
Nature of ions	They are electropositive elements and hence, lose one or more electrons to form positive ions.	They are electronegative elements and hence, gain one or more electrons to form negative ions.
Nature of chlorides	They generally combine with chlorineto form solid ionic chlorides which conduct electricity in the aqueous solution or in the molten state.	They combine with chlorine to form covalen chlorides. These are either gases or liquids. Non-metal chlorides do not contain ions, therefore, they do not conduct electricity.
Nature of oxides	They form basic oxides, though some oxides are amphoteric also.	They form acidic or neutral oxides.
Displacement of hydrogen from acids	Metals which lie above hydrogen in the reactivity series displace hydrogen from acids.	They do not displace hydrogen from acids.

(i) Match column-I with column-Il and select the correct option using the given code

Column-I	Column-II
P. A metal that forms amphoteric oxides	(I) Ga
Q. A metal which melts when keep on our palm	(II) Au
R. A metal that has highest density	(III) Al
S. A metal which cannot displace hydrogen from acids	(IV) Os

(a) P-(II), Q-(I), R-(lII), S-(lV)	(b) P-(III), Q-(I), R-(IV), S-(lI)
(c) P-(lV), Q-(II), R-(lII), S-(I)	(d) P-(lII), Q-(II), R-(I), S-(lV)

(ii) State True (T) or False (F) for the following statements.
(I) Non-metals react with acids to give a salt and hydrogen gas.
(II) Zinc oxide is amphoteric in nature.
(III) Copper oxide is basic in nature.
(IV) Hydrogen gas is evolved when a metal reacts with dilute acid.
(V) Copper reacts vigorously with dilute HCl.

	(I)	(II)	(III)	(IV)	(V)
(a)	F	F	F	T	T
(b)	T	F	T	F	F
(c)	F	T	F	F	T
(d)	F	T	T	T	F

(iii) Tick (✓) the correct statements and cross (x) the incorrect statements.
(I) Non-metals are either solids or gases except mercury which is a liquid.
(II) Sodium is a metal and can lose its electrons easily.
(III) Most non-metals produce acidic oxides when dissolved in water. Most metals produce basic oxides on reaction with water.
(IV) Graphite is a conductor of electricity.

	(I)	(II)	(III)	(IV)
(a)	✓	メ	✓	メ
(b)	メ	✓	メ	✓
(c)	メ	✓	✓	✓
(d)	メ	✓	✓	メ

(iv) An element X (atomic number 12) reacts with another element Y (atomic number 17) to form a compound Z. Which of the following statements are true regarding this compound?
I. Molecular formula of Z is XY₂
II. It is soluble in water.
III. X and Yare joined by sharing of electrons.
IV. It would conduct electricity in the molten state.

(a) II and III only

(b) I and II only

(c) I, III and IV only

(d) I, II and IV only

(v) Which of the following metals form an amphoteric oxide?

(a) Zn

(b) Ca

(c) Na

(d) Cu

5)
As neutral atom carbon has electronic configuration K L. To gain inert gas configuration carbon can either 2, 4 donate 4 valence electrons (helium gas configuration) or gain 4 electrons (neon gas configuration), but it cannot do so. To acquire inert gas configuration carbon can only share its 4 valence electrons with other atoms forming covalent bonds. A covalent bond can be defined as a chemical bond formed between two atoms by mutual sharing of valence electrons so that each atom acquires the stable electronic configuration of the nearest noble gas. The concept of covalent bonds was given by Langmuir and Lewis to explain bonding in non-ionic compounds. The covalent bonds are of three types. If each atom contributes one electron, the covalent bond formed is called a single covalent bond and is represented by a single line (-) and if each atom contributes two electrons, the covalent bond formed is called a double bond and is represented by a double line (=) and if each atom contributes three electrons, the covalent bond formed is called a triple bond and is represented by a triple line (=).
(i) Which of the following do not contain a double bond?
I. S02
II. NH3
III. HCl
IV. 02

(a) I and II only (b) II and III only (c) III and IV only (d) I and IV only

(ii) Which of the following contains a triple bond?

(a) N₂ (b) O₂ (c) CO₂ (d) H₂

(iii) The shared pair of electrons is said to constitute a _______________ bond between two hydrogen atoms.

(a) single (b) double (c) triple (d) ionic

(iv) Which of the following molecules has all its atoms joined together by double covalent bonds?

(a) Methane (b) Water (c) Carbon dioxide (d) Nitrogen trichloride

(v) Chlorine forms a diatomic molecule, Cl₂ . The electron dot structure for this molecule is

CBSE 10th Standard Science Subject Case Study Questions with Solutions 2021 Part - I - by Prerna - Bangalore - May 21, 2021 - View & Read

1)

In decomposition reactions, a single reactant breaks down to form two or more products. A decomposition reaction is opposite to combination reaction. Thermal decomposition reactions use the energy in form of heat for the decomposition of reactants. Electrolytic decomposition reactions involve the use of electrical energy for the decomposition of reactant molecules. Photolysis or photochemical decomposition involves the use of light energy for the purpose of decomposition.
(i) Which of the following reactions is a decomposition reaction?

\({ (a) \ } \mathrm{NaOH}+\mathrm{HCl} \longrightarrow \mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}\)	\({ (b) \ } \mathrm{NH}_{4} \mathrm{CNO} \longrightarrow \mathrm{H}_{2} \mathrm{NCONH}_{2}\)
\({ (C) \ } 2 \mathrm{KCIO}_{3} \longrightarrow 2 \mathrm{KCl}+3 \mathrm{O}_{2}\)	\( { (d) \ } \mathrm{H}_{2}+\mathrm{I}_{2} \longrightarrow 2 \mathrm{HI}\)

\({ (ii) \ } 2 \mathrm{~Pb}\left(\mathrm{NO}_{3}\right)_{2} \longrightarrow 2 \mathrm{PbO}+n A+\mathrm{O}_{2}\)
What is nA in the given reaction?

(a) 4NO

(b) 4NO₂

(c) 2PbNO₂

(d) NO₂

(iii) Amino acid is formed by the decomposition of which component of our diet?

(a) Carbohydrate

(b) Starch

(c) Protein

(d) Fat

(iv) Silver chloride on exposure to sunlight for a long duration turns grey due to
(I) the formation of silver by decomposition of silver chloride
(II) sublimation of silver chloride
(III) decomposition of chlorine gas from silver chloride
(IV) oxidation of silver chloride
The correct statement(s) is/are

(a) Only (I)

(b) Only (II) and (III)

(c) Only (I) and (II)

d) Only (IV)

(v) What type of chemical reaction takes place when electricity is passed through water?

(a) Thermal decomposition	(b) Electrolytic decomposition
(c) Photochemical decomposition	(d) Displacement reaction

2)
Oxidation has damaging effect on metals as well as on food. The damaging effect of oxidation on metal is studied as corrosion and that on food is studied as rancidity. The phenomenon due to which metals are slowly eaten away by the reaction of air, water and chemicals present in atmosphere, is called corrosion. For example, iron articles are shiny when new, but get coated with a reddish brown powder when left for sometime. This process is known as rusting of iron. Rancidity is the process of slow oxidation of oil and fat (which are volatile in nature) present in the food materials resulting in the change of smell and taste in them.
(i) Rancidity can be prevented by

(a) adding antioxidants (b) packaging oily food in nitrogen gas

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

(ii) Combination of phosphorus and oxygen is an example of

(a) oxidation (b) reduction (c) rancidity (d) none of these

(iii) A science teacher wrote the following statements about rancidity :
(I) When fats and oils are reduced, they become rancid.
(II) In chips packet, rancidity is prevented by oxygen.
(III) Rancidity is prevented by adding antioxidants.
Select the correct option.

(a) (I) only (b) (II) and (III) only (c) (III) only (d) (I), (II), and (III)

(iv) Two statements are given below regarding rusting of iron.
(I) The rusting of iron is a redox reaction and reaction occurs as, \(4 \mathrm{Fe}+3 \mathrm{O}_{2} \longrightarrow 4 \mathrm{Fe}^{3+}+6 \mathrm{O}^{2-}\)
(II) The metallic iron is oxidised to \(\mathrm{Fe}^{2+} \text { and } \mathrm{O}_{2} \text { is reduced to } \mathrm{O}^{2-}\)
Select the correct statement(s).

(a) I only (b) II only (c) Both I and II (d) None of these

(v) Which of the following measures can be adopted to prevent or slow down rancidity?
(I) Food materials should be packed in air tight container.
(II) Food should be refrigerated.
(III) Food materials and cooked food should be kept away from direct sunlight

(a) Only II and III (b) Only I and III (c) Only II and III (d) I, II and III

3)

Chemically, Plaster of Paris (POP) is calcium sulphate hemihydrate, i.e., containing half molecule of water of crystallisation. It is represented by the formula, CaSO_{4 ·}1/2H₂O. Half molecule of water of crystallisation means that one water molecule is shared by two formula units of CaSO_4. Hence, we also represent its formula as (CaSO₄)_2·H₂O. The name, plaster of Paris, was given to this compound because for the first time, it was made from gypsum which was mainly found in Paris.
(i) The difference of water molecules in gypsum and plaster of Paris is

(a) 5/2

(b) 2

(c) 1/2

(d) 3/2

(ii) Plaster of Paris hardens by

(a) giving off CO₂	(b) changing into CaCO₃
(c) combining with water	(d) giving out water

(iii) Which of the following statements is incorrect?

(a) Plaster of Paris is used to ornate designs on walls and ceilings

(b) On heating gypsum above 373 K, CaSO₄ is obtained

(c) Dead burnt plaster is CaSO₄·2H₂O

(d) Setting of plaster is due to its hydration into gypsum

(iv) Select the incorrect statement with respect to gypsum

(a) It is slightly soluble in water

(b) It is also known as alabaster

(c) On heating gypsum at 373 K, it loses water molecules and becomes calcium sulphate hemihydrate

(d) Chemical formula of gypsum is CaSO₄ ·1/2H₂O

(v) Plaster of Paris is obtained by

(a) adding water to calcium sulphate.

(b) adding sulphuric acid to calcium hydroxide

(c) heating gypsum to a very high temperature

(d) heating gypsum to 100° C

4)

The preparation of washing soda is carried out through following steps:
Step-I: Manufacture of sodium hydrogen carbonate:\(\mathrm{NaCl}+\mathrm{H}_{2} \mathrm{O}+\mathrm{NH}_{3}+\mathrm{CO}_{2} \longrightarrow \ \mathrm{NaHCO}_{3}+ \ \mathrm{NH}_{4} \mathrm{Cl}\)
Sodium hydrogen carbonate
Step-II: Thermal decomposition of sodium hydrogen carbonate: When dry crystals of sodium hydrogen carbonate are heated strongly, they decompose to form anhydrous sodium carbonate (soda ash). \(2 \mathrm{NaHCO}_{3(s)} \longrightarrow \mathrm{Na}_{2} \mathrm{CO}_{3(s)}+\mathrm{CO}_{2(g)}+\mathrm{H}_{2} \mathrm{O}_{(g)}\)
Step-III: Recrystallisation of sodium carbonate: Sodium carbonate thus obtained is recrystallised to form crystals of washing soda.\(\mathrm{Na}_{2} \mathrm{CO}_{3(s)}+ 10 \mathrm{H}_{2} \mathrm{O}_{(l)} \longrightarrow \mathrm{Na}_{2} \mathrm{CO}_{3} \cdot 10 \mathrm{H}_{2} \mathrm{O}_{(s)}\)
Anhydrous Washing soda
sodium carbonate
(i) Some of the uses of washing soda are given below:
(I) It is used for removing permanent hardness of water
(II) It is used in glass industry
(III) It is used in paper industry
(IV) It is used in the manufacture of sodium compounds such as borax
Select the correct option regarding uses of washing soda

(a) (I) and (II) only	(b) (II) and (III) only
(c) (II) and (IV) only	(d) (I), (II), (III) and (IV)

(ii) What products will be formed along with water when sodium carbonate reacts with dilute hydrochloric acid?

(a) CO and NaCI	(b) Na and CO₂
(c) NaCI and CO₂	(d) Na and CO

(iii) Chief raw materials for the manufacture of washing soda are

(a) sodium chloride, ammonia and limestone

(b) ammonia, sodium hydrogen carbonate and copper sulphate

(c) sodium hydroxide, calcium chloride and ammonia

(d) calcium chloride, sodium chloride and copper sulphate.

(iv) What is the action of sodium carbonate on litmus paper?

(a) Turns red litmus blue

(b) Turns blue litmus red

(c) No change on litmus

(d) Both (a) and (b)

(v) What products will be obtained when solution of sodium carbonate and slaked lime is heated?

(a) NaOH and CaCl₂	(b) CaCO₃and NaOH
(c) NaHCO₃ and NaOH	(d) NaCI and CaCO₃

5)
Metals as we know, are very useful in all fields, industries in particular. Non-metals are no less in any way. Oxygen present in air is essential for breathing as well as for combustion. Non-metals form a large number of compounds which are extremely useful, e.g., ammonia, nitric acid, sulphuric acid, etc.
Non-metals are found to exist in three states of matter. Only solid non-metals are expected to be hard however, they have low density and are brittle. They usually have low melting and boiling points and are poor conductors of electricity.
(i)____________ is a non-metal but is lustrous

(a) Phosphorus (b) Sulphur (c) Bromine (d) Iodine

(ii) Which of the following is known as 'King of chemicals'?

(a) Urea (b) Ammonia X (c) Sulphuric acid (d) Nitric acid

(iii) Which of the following non-metals is a liquid?

(a) Carbon (b) Bromine (c) Iodine (d) Sulphur

(iv) Hydrogen is used

(a) for the synthesis of ammonia (b) for the synthesis of methyl alcohol

(c) in welding torches (d) all of these

(v) Generally, non-metals are bad conductors of electricity but 'X'which is a form of carbon is a good conductor of electricity and is an exceptional non-metal. 'X'is

(a) diamond (b) graphite (c) coal (d) coke.

(a) Flooded paddy field	(b) Cattle
(c) Jet fuel	(d) Marshes

(a) accumulation of O₃ and depletion of CO₂	(b) accumulation of both O₃ and CO₂
(c) accumulation of CO₂ and depletion of O₃	(d) presence of green plants on the earth

(a) Populations of W, Y and Z also declines	(b) Population of Y declines only.
(c) Population of Z remains unchanged.	(d) Population of Z increases.

(a) another herbivore like toad	(b) a predator of insects only
(b) a predator of insects only	(d) a predator of skunks and prey of the toad

(a) Mice and insects	(b) Birds and bees
(c) Deer and mice	(d) Insects and wolves

(a) Fleming's right-hand rule	(b) Fleming's left-hand rule
(c) Clock face rule	(d) Left-hand thumb rule

(a) N-pole	(b) S-pole
(c) N-pole if current is large	(d) S-pole if current is small

(a) along its velocity	(b) opposite to its velocity
(c) perpendicular to its velocity	(d) zero

(a) Electromagnetism	(b) Induced magnetism
(c) Electromagnetic induction	(d) Static induction

(a) the number of turns in the coil	(b) the speed with which the magnet is moved
(c) the strength of the magnet	(d) the resistivity of the material of the coil

Group 16	Group 17
-	-
-	A
-	-
B	C

(a) The amount of the current in the coil	(b) The direction of the current in the coil.
(c) The number of turns in the coil.	(d) The strength of the magnetic field

(a) mechanical energy to chemical energy	(b) electrical energy to mechanical energy
(c) chemical energy to mechanical energy	(d) mechanical energy to electrical energy.

(a) doubled	(b) halved
(c) four times	(d) one fourth times

(a) 4 times	(b) 2 times
(c) \(\begin{equation} \frac{1}{2} \text { times } \end{equation}\)	(d) \(\begin{equation} \frac{1}{4} \text { times } \end{equation}\)

(a) lens	(b) prism
(c) mirror	(d) none of these

(a) Reflection	(b) Refraction
(c) Dispersion	(d) Scattering

(a) pure spectrum	(b) impure spectrum
(c) monochromatic spectrum	(d) none of these.

(a) Red> Green> Yellow	(b) Red> Violet> Green
(c) Yellow> Green> Violet	(d) Red> Yellow> Orange

(a) Red> Green> Blue	(b) Blue> Green> Red
(c) Violet> Red> Green	(d) Green> Red> Blue

(a) Red> Green> Blue	(b) Blue> Yellow> Orange
(c) Orange> Red> Green	(d) Blue> Green> Violet

12th Standard stateboard question papers & Study material

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11th Standard stateboard question papers & Study material

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கணிதம்

உயிரியல்

பொருளியல்

இயற்பியல்

வேதியியல்

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Commerce

Economics

Biology

Business Maths and Statistics

Accountancy

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Physics

Chemistry

Computer Applications

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Computer Technology

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English

9th Standard stateboard question papers & Study material

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கணிதம்

அறிவியல்

சமூக அறிவியல்

6th Standard stateboard question papers & Study material

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அறிவியல்

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Science

Social Science

10th Standard stateboard question papers & Study material

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கணிதம்

(a) increases	(b) decreases
(c) remains the same	(d) all of these

(a) atmospheric refraction	(b) scattering of light
(c) both (a) and (b)	(d) none of these

(a) dispersion	(b) scattering
(c) atmospheric refraction	(d) cannot say

(a) scattering of light	(b) dispersion of light
(c) atmospheric refraction	(d) none of these

(a) Radius of curvature	(b) Focallength
(c) Principal focus	(d) Principal axis

(a) pole and center of curvature	(b) focus point and center of curvature
(c) pole and object	(d) object and image

(a) focus	(b) pole
(c) center of curvature	(d) any point

(a) a flat surface	(b) a bent-in surface
(c) a bulging-out surface	(d) an uneven surface

(a) larger than the object	(b) smaller than the object
(c) same size as that of the object	(d) highly enlarged.

(a) plane	(b) concave
(c) convex	(d) either plane or convex.