Question Set C

cbse 12th Standard Chemistry Coordination Compounds Model Questions Papers Study Material - QB365

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Questions:

Generic 3

5 x 3 = 15

Define the following terms:
(a) Vitamins
(b) Invert sugar
(c) Nucleoside

An aromatic compound 'A' on heating with Br₂ and KOH forms a compound 'B' of molecular formula C₆H₇N which on reacting with CHCI₃and alcoholic KOH produces a foul smelling compound 'C'. Write the structures and IUPAC names of compounds A, B and C.

What are enzymes? Describe their functions. Name two diseases which are caused due to deficiency of enzymes.

Why aryl halides are less reactive towards nucleophilic substitution reactions than alkyl halides?

What is menat by unidentate, didentate and ambidentate ligands? Give twoo examples for each.

Multiple Choice Question

10 x 1 = 10

Which of the following statements are correct about the mechanism of this reaction?

(a)

A carbocation will be formed as an intermediate in the reaction.

(b)

OH^-will attach the substrate (ii) from one side and CI^- will leave it simultaneously from other side.

(c)

An unstable intermediate will be formed in which OH^- and Cl^- will be attached by weak bonds.

(d)

(d) Reaction proceeds through S_N1 mechanism

is a

(a)

primary amine

(b)

secondary amine

(c)

tertiary amine

(d)

None of these

The M - Cㅠ - bond is formed by the

(a)

donation of a pair of electrons

(b)

sharing of a pair of electrons

(c)

receiving a pair of electrons

(d)

None of the above

Which of the following is not the correct reaction of aryldiazonium salts?

(a)

\({ C }_{ 6 }H_{ 5 }{ N }_{ 2 }^{ + }{ CI }^{ - }+{ Cu }_{ 2 }{ Cl }_{ 2 }\longrightarrow { C }_{ 6 }H_{ 5 }CI\)

(b)

\({ C }_{ 6 }H_{ 5 }{ N }_{ 2 }^{ + }{ CI }^{ - }+HB{ F }_{ 4 }\overset { Heat }{ \longrightarrow } { C }_{ 6 }H_{ 5 }F\)

(c)

\({ C }_{ 6 }H_{ 5 }{ N }_{ 2 }^{ + }{ CI }^{ - }+{ H }_{ 3 }{ PO }_{ 2 }\longrightarrow { C }_{ 6 }H_{ 5 }{ PO }_{ 4 }\)

(d)

\({ C }_{ 6 }H_{ 5 }{ N }_{ 2 }^{ + }{ CI }^{ - }+SnCI_{ 2 }/HCI\longrightarrow { C }_{ 6 }H_{ 5 }{ NHNH }_{ 2 }\)

10.

Number of structural isomers possible from the molecular formula C₃H₉N is

(a)

(b)

(c)

(d)

11.

Starch is a mixture of two components, a water soluble component amtlose (15-20%) and a water insoluble component amylopectin (80-85%). The aqueous solution of amylose gives a blue colour with iodine solution due to the formation of

(a)

amylose iodide

(b)

amylose iodate

(c)

inclusion complex

(d)

amylose teriodide complex

12.

Which of the following statements is not true regarding (+)-lactose ?

(a)

(+)-Lactose, C₁₂H₂₂O₁₁ contains * OH groups

(b)

On hydrolysis, (+)-lactose gives equal amounts of D-(+)-glucose and D-(+)-galactose

(c)

(+)-Lactose is a \(\beta\) -glycoside formed by the union of a molecule of D (+)-glucose and a molecule of D-(+)-galactose

(d)

(+)-Lactose is a reducing sugar and does not exhibit mutarotation

13.

For the following : (a) I^- (b) CI^- (c) Br^- the increasing order of nucleophilicity would be

(a)

Br^- < CI^- < I^-

(b)

I^- < Br^- < CI^-

(c)

CI^- < Br^- < I^-

(d)

I^- < CI^- < Br^-

14.

Which of the following possesses highest melting point?

(a)

Chlorobenzene

(b)

o-Dichlorobenzene

(c)

m-Dichlorobenzene

(d)

p-Dichlorobenzene

15.

The correct structure of Fe(CO)₅ is

(a)

octahedral

(b)

terahedral

(c)

square pyramidal

(d)

trigonal bipyramidal

Generic 5

4 x 5 = 20

16.

An alkyl halide (A) of molecular formula, C₆H₁₃Cl on treatment with alcoholic KOH gives two isomeric alkenes (B) and (C) of molecular formula, C₆H₁₂- Both alkenes on hydrogenation gives 2, 3-dimethylbutane. Write the structures of (A), (B) and (C).

17.

(a) Write the structures of main products when products when benzene diazonium chloride reacts with the following reagents:
(i) H₃PO₂+H₂O
(ii) CuCN/KCN
(iii) H₂O
(b) Arrange the following in the increasing order of their basic character in an aqueous solution:
C₂H₅NH₂ , (C₂H₅)₂NH, (C₂H₅)₃N
(c) Give a simple chemical test to distinguish between the following pair of compounds:
C₆H₅-NH₂ and C₆H₅-NH-CH₃

18.

What forces are responsible for the stability of \(\alpha\) - helix ? Why is it named as 3.6₁₃ helix?

19.

Using crystal field theory, draw energy level diagram, write electronic configuration of the central metal atom/ion and determine the magnetic moment value in the following :
(i) \([CoF_6]^{3-}, [Co(H_2O)_6]^{2+},[Co(CN)_6]^{3-}\)
(ii) \([FeF_6]^{3-}, \ [Fe(H_2O)_6]^{2+}, [Fe(CN)_6]^{4-}\).

Generic 2

4 x 2 = 8

20.

Complete the following chemical equation:
(i) CH₃CI + KNO₂ \(\longrightarrow\)
(ii) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}+\mathrm{NaI} \stackrel{\text { Acetone }}{\longrightarrow}\)

21.

Why do proteins form an indispensable part of our food?

22.

Benzene diazonium salts are more stable than alkyl diazonium salts. Give reason.

23.

Write the IUPAC name of [PtCI₆]^2-

Assertion and reason

4 x 1 = 4

24.

Assertion : NF₃ is a weaker ligand than N(CH₃)₃.
Reason : NF₃ ionizes to give F^– ions in aqueous solution.
Codes:
(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.
(b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.
(c) If the Assertion is correct but Reason is incorrect.
(d) If both the Assertion and Reason are incorrect.

25.

Assertion (A) : Nucleophilic substitution of iodoethane is easier than chloroethane.
Reason (R) : Bond enthalpy of C-1 bond is less than that of C-Cl bond
(a) Both (A) and (R) are correct, (R) is the correct explanation of (A).
(b) Both (A) and (R) are correct, (R) is not the correct explanation of (A).
(c) (A) is correct but (R) is incorrect.
(d) (A) is incorrect but (R) is correct

26.

Assertion: Carbylamine reaction involves the reaction between 1^o amine and chloroform in basic medium.
Reason: In carbylamine reaction, -NH₂ group is converted into - NC group.
Codes:
(a) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(b) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(c) Assertion is correct statement but reason is wrong statement.
(d) Assertion is wrong statement but reason is correct statement.

27.

In the following questions. an Assertion (A) is followed by a corresponding Reason (R) Use the following keys to choose the appropriate answer.
Assertion (A) Fresh tomatoes are better source of vitamin C than those which have been stored for sometime.
Reason (R) On prolonged exposure to air, vitamin C is destroyed due to aerial oxidation.
Codes:
(a) Both (A) and (R) are correct, (R) is the correct explanation of (A).
(b) Both (A) and (R) are correct, (R) is not the correct explanation of (A).
(c) (A) is correct; (R) is incorrect.
(d) (A) is incorrect; (R) is correct.

Case Study Questions

2 x 4 = 8

28.

Observe the histogram showing boiling points of pentane, iso pentane, 1°,2° and 3 ° amines. Answer the questions that follow based on table and related concepts.

(a) Why does CH₃CH₂CH₂CH₂NH₂(1° amine) has higher boiling point than (C₂H₅)₂NH and C₂H₅N(CH₃ )₂?
(b) Why does ethanol have higher boiling point than ethanamine?
(c) Why amines are more basic than alcohol?
(d) Why are Primary amines more soluble in water than 2° and 3° amines?
(e) Arrange the compounds shown in graph, increasing order of boiling points. Give reason.

29.

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

(a) ketotriose

(b) ketotetrose

(c) ketopentose

(d) ketohexose

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

(a) 16

(b) 8

(c) 32

(d) 4

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

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

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

(a) Glucose forms cyanohydrin with HCN

(b) Glucose reacts with hydroxylamine to form an oxime

(c) Pentaacetate of glucose does not react with hydroxylamine

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

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Answers Key:

Generic 3

5 x 3 = 15

(a) Vitamins: Vitamins are the group of organic compounds which are required in very small amounts for the healthy growth and functioning of animal organism. They cannot be made by organism and so have to be part of our diet. The deficiency of a vitamin can cause a specific disease. Vitamins A, D, E and K are fat-soluble substances, whereas vitamin B complex and vitamin C are water-soluble.
(b) Invert sugar: It is a mixture containing equal amount of glucose and fructose.
(c) Nucleosides: A base joined to a sugar molecule is called nucleoside, e.g. adenosine contains adenine and ribose, guanosine contains ribose and guanine, cytidine contains ribose and cytosine.

'A' is Benzamide, 'B' is Benzenamine, 'C' is isocyanobenzene.

Enzymes are biological catalyst, they are composed of proteins. Enzymes are highly specific in nature. The two
main functions are as follows :
(i) They lower the requirement of activation energy.
(ii) They speed up the rate of reaction.
e.g. Enzyme maltase catalyses maltose to glucose.
\(\begin{equation} \mathrm{C}_{12} \mathrm{H}_{22} \mathrm{O}_{11}+\mathrm{H}_{2} \mathrm{O} \stackrel{\text { Maltase }}{\longrightarrow} 2 \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{6} \end{equation}\)
(iii) Two diseases which are caused due to deficiency of enzymes are
(a) Phenyl ketone urea (PKU) (b) Albinism

Haloarenes are much less reactive than haloalkanes towards nucleophilic substitution reactions because of the following reasons:
1. Resonance effect: In haloarenes, there is delocalisation of electrons due to resonance. For example, chlorobenzene is considered to be a resonance hybrid of the following structures:

It is evident that, the contribution of structures III, IV and V imparts a partial double bond character to the carbon-chlorine bond. This is confirmed by X-ray analysis which shows that the C - CI bond length in chlorobenzene is 1.69A while the C-CI bond length in ethyl chloride molecule is 1.82A. The shortening of bond length imparts stability to aryl halides and the bond cleavage becomes rather difficult. The aryl halides are, therefore, less reactive than alkyl halides.
2. Different hybridisation states of carbon atom: In haloalkanes the carbon atom of the C - X bond is sp³ hybridised while in haloarene halides, the carbon atom is sp² hybridised. The Sp² hybridised carbon atom with a greater s-character is more electronegative. It can hold the electron pair of the bond more tightly than the Sp³ hybridised carbon atom in alkyl halides. Therefore, it has less tendency to release electrons to the halogen. As a result, the bond cleavage in aryl halides is some what more difficult than in alkyl halides.

Thus haloarenes are less reactive towards the substitution reactions than haloalkanes.

Unidentate Ligands: Those ligands which can form only one coordinate bond are called unidentate ligands, e.g. NH₃ , CN^-Didentate Ligands: Those ligands which can form two coordinate bonds are called bidentate ligands,\(\overset { { COO }^{ - } }{ \underset { { COO }^{ - } }{ | } } \) (ox), H₂NCH₂CH₂NH₂(en). Ambidentate Ligands: Those ligands which can form bond through either of the two donor atoms are called ambidentate ligands, e.g. CN^- , NO₂^- etc.

Multiple Choice Question

10 x 1 = 10

(a)
A carbocation will be formed as an intermediate in the reaction.

(a)
primary amine

(a)
donation of a pair of electrons

H₃PO₄ brings about substitution of diazo group by H. Therefore, reaction (c) is not correct.

10.

(d)
4

11.

12.

(d)
(+)-Lactose is a reducing sugar and does not exhibit mutarotation

13.

14.

(d)
p-Dichlorobenzene

15.

Generic 5

4 x 5 = 20

16.

The reaction takes place as follows

17.

(b) C₂H₅NH₂ < (C₂H₅)₃N < (C₂H₅)₂NH
(c) Add CHCl₃ and alc. KOH, C₆H₅-NH₂ gives foul smell of isocyanide whereas C₆H₅-NH-CH₃ does not (or any other correct test).

18.

The stability of \(\alpha \) -helix structure is due to intramolecular H-bonding between -NH- and -CO- groups of the same polypeptide chain. The \(\alpha \) -helix is termed as \({ 3.6 }_{ 13 }\) helix since each turn of the helix has approximately 3·6 amino acids and the hydrogen bonding leads to the formation of a 13-membered ring.

19.

(i) \([CoF_6]^{3-}\)
\( [Co(H_2O)_6]^{2+}\)
\([Co(CN)_6]^{3-}\)
(ii) \([FeF_6]^{3-}\)
\(\ [Fe(H_2O)_6]^{2+}\)
\([Fe(CN)_6]^{4-}\)
It is diamagnetic due to the absence of unpaired electrons.

Generic 2

4 x 2 = 8

20.

(i) \(\mathrm{CH}_{3} \mathrm{Cl}+\mathrm{KNO}_{2} \longrightarrow \mathrm{CH}_{3}-\mathrm{O}-\mathrm{N}=\mathrm{O}+\mathrm{KCl}\)
(ii) \(\mathrm{C}_{2} \mathrm{H}_{5} \mathrm{Cl}+\mathrm{NaI} \stackrel{\text { Acetone }}{\longrightarrow} \mathrm{C}_{2} \mathrm{H}_{5} \mathrm{I}+\mathrm{NaCl}\)

21.

Providing strength to the cells and tissues.

22.

Due to the dispersal of positive charge over benzene ring.

23.

Hexochloroplatinate (IV)

Assertion and reason

4 x 1 = 4

24.

25.

(a) Both (A) and (R) are correct, (R) is the correct explanation of (A).
Nucleophilic substitution of iodoethane is easier than chloroethane because bond energy or enthalpy of C-I bond is less than that of C-Cl bond. Thus, both (A) and (R) are correct and (R) is the correct explanation of (A).

26.

(a) \( R \mathrm{NH}_{2}+\mathrm{CHCl}_{3}+3 \mathrm{KOH}(\mathrm{alc}) \longrightarrow\) \(R-\mathrm{N} =^\rightarrow \mathrm{C}+3 \mathrm{KCl}+3 \mathrm{H}_{2} \mathrm{O}\)

27.

(a) Both (A) and (R) are correct and (R) is correct explanation of (A).

Case Study Questions

2 x 4 = 8

28.

(a) It is because extent of H-bonding is more in CH₃CH₂CH₂CH₂NH₂ than 2° and 3° amines.
(b) It is because H-bonds are stronger in alcohols than amines because 'O' is more electronegative than 'N'.
(c) It is because \(\stackrel{\oplus}{\mathrm{RNH}_{3}}\) is more stable than \(\underset{\mathrm{ROH2}}{\oplus}\) . +ve charge on oxygen is not stable.
(d) It is because primary amines can form H-bonds with water to more extent.
(e) C₂H₅CH(CH₃)₂ < CH₃(CH₂)₃CH₃ < C₂H₅N(CH₃)₂ < (C₂H₅)₂NH < C₄H₉NH₂.
Isopentane has lower boiling point that n-Pentane due to branching less surface area, less van der Waals' forces of attraction. 3° < 2° < 1° is order of boiling point in amines because extent of H-bonding increases.

29.

(i) (a)
(ii) (a)
(iii) (c) : Glucose contains four chiral centres.
(iv) (c) : Pentacetate of glucose does not react with hydroxylamine showing absence of free -CHO group. This cannot be explained by open structure of glucose.