CBSE Class 12 Chemistry 2024 question paper (56/2)

Maximum marks 70 · Time 3 hours · 3 sets

Try each question first, then open its model answer. Where the paper offers a choice, both questions are shown with OR between them.

Section A

1 mark each

Q.11 mark $\mathrm{MnO_2}$
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Q.21 mark $\mathrm{EDTA^{4-}}$
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Q.31 mark $Which of the following ligand forms chelate complex ?$
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Q.41 mark $\mathrm{sp^2}$
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Q.51 mark $Which of the following is most acidic ?$
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Q.61 mark $Anisole reacts with HI to give :$
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Q.71 mark $\mathrm{H_2SO_4}$
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Q.81 mark $An azeotropic solution of two liquids has boiling point lower than either of them when it :$
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Q.91 mark $0{\cdot}0225$
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Q.101 mark $During electrolysis of aqueous solution of NaCl :$
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Q.111 mark $The addition of catalyst during a chemical reaction alters which of the following quantities of the reaction ?$
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Q.121 mark $\mathrm{P} \rightarrow \mathrm{Q}$
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For Questions number 13 to 16, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below.
Q.131 mark $Assertion (A) : Aliphatic primary amines can be prepared by Gabriel phthalimide synthesis. Reason (R) : Alkyl halides undergo nucleophilic substitution with anion formed by phthalimide.$
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Q.141 mark $Assertion (A) : Uracil base is present in DNA. Reason (R) : DNA undergoes self-replication.$
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Q.151 mark $Assertion (A) : Diazonium salts of aromatic amines are more stable than those of aliphatic amines. Reason (R) : Diazonium salts of aliphatic amines show resonance.$
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Q.161 mark $p$
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Section B

2 marks each

Q.172 marks $\mathrm{mol^{-1}}$
Q.182 marks $1{\cdot}25 \times 10^{-3}\ \mathrm{s^{-1}}$
Q.19 (a)2 marks $What is lanthanoid contraction ? Actinoid contraction is greater from element to element than lanthanoid contraction. Why ?$
OR
Q.19 (b)2 marks $Why do transition metals have high enthalpy of atomization ? Which element of 3d-series has lowest enthalpy of atomization ?$
Q.202 marks $\mathrm{S_N2}$
Q.212 marks $Define the following terms : (a) Denaturation of protein (b) Invert sugar$

Section C

3 marks each

Q.223 marks $\mathrm{CH_3 - CH_2 - Br} \xrightarrow{\mathrm{KCN}} \mathrm{A} \xrightarrow[\text{Partial hydrolysis}]{\mathrm{OH^{-}}} \mathrm{B} \xrightarrow{\mathrm{NaOH} + \mathrm{Br_2}} \mathrm{C}$
Q.233 marks $Write the reaction involved in the following : (a) Wolff-Kishner reduction (b) Decarboxylation reaction (c) Cannizzaro reaction$
Q.243 marks $Give the equations of reactions for the preparation of : (any three) (a) Phenol from chlorobenzene (b) Salicylaldehyde from phenol (c) 2-Methoxyacetophenone from anisole (d) Picric acid from phenol$
Q.253 marks $Give reasons for the following : (a) Chlorine is ortho/para directing in electrophilic aromatic substitution reactions, though chlorine is an electron withdrawing group. (b) Racemic mixture is optically inactive. (c) Allyl chloride is hydrolysed more readily than n-propyl chloride.$
Q.263 marks $The vapour pressure of a solvent at 283 K is 100 mm Hg. Calculate the vapour pressure of a dilute solution containing 1 mole of a strong electrolyte AB in 50 moles of the solvent at 283 K (assuming complete dissociation of solute AB).$
Q.273 marks $\mathrm{Zn\,(s)} \mid \mathrm{Zn^{2+}}\ (0{\cdot}1\ \mathrm{M}) \parallel \mathrm{Sn^{2+}}\ (0{\cdot}001\ \mathrm{M}) \mid \mathrm{Sn\,(s)}$
Q.283 marks $17\,^{\circ}\mathrm{C}$

Section D

Carbohydrates are essential for life in both plants and animals. Carbohydrates are used as storage molecules as starch in plants and glycogen in animals. Chemically they are polyhydroxy aldehydes or ketones. On the basis of their behaviour on hydrolysis, carbohydrates are classified as monosaccharides, oligosaccharides and polysaccharides. All monosaccharides are reducing sugars, i.e., they are oxidized by Tollens' reagent and Fehling's solution. A monosaccharide like glucose is aldohexose and its molecular formula was found to be $\mathrm{C_6H_{12}O_6}$ . After reacting with different reagents like HI, $\mathrm{H_2N - OH}$ , Bromine water, $\mathrm{(CH_3CO)_2O}$ , etc. its structure was found to contain one aldehyde group, one primary alcoholic group, $(-\mathrm{CH_2OH})$ and four secondary alcoholic groups $(>\mathrm{CHOH})$ . Despite having the aldehyde group, glucose does not give some of the reactions of aldehyde group like Schiff's test, $\mathrm{NaHSO_3}$ addition. This explains the existence of glucose in two cyclic hemiacetal forms which differ only in the configuration of the hydroxyl group at C $-$ 1.
Q.29 (a)1 mark $What are reducing sugars ?$
Q.29 (b)1 mark $Classify the following into monosaccharide and disaccharide : Fructose, Sucrose, Lactose, Galactose$
Q.29 (c)2 marks $Name the polysaccharide which is known as 'animal starch'. Why is it called 'animal starch' ?$
OR
Q.29 (c) OR2 marks $-\mathrm{OH}$

Transition metals have incomplete d-subshell either in neutral atom or in their ions. The presence of partly filled d-orbitals in their atoms makes transition elements different from that of the non-transition elements. With partly filled d-orbitals, these elements exhibit certain characteristic properties such as display of a variety of oxidation states, formation of coloured ions and entering into complex formation with a variety of ligands. The transition metals and their compounds also exhibit catalytic properties and paramagnetic behaviour. The transition metals are very hard and have low volatility. An examination of the

\mathrm{E^{o}_{M^{2+}/M}}

values shows the varying trends :

	$\mathrm{E^{o}_{M^{2+}/M}}$
V	$-1{\cdot}18$
Cr	$-0{\cdot}91$
Mn	$-1{\cdot}18$
Fe	$-0{\cdot}44$
Co	$-0{\cdot}28$
Ni	$-0{\cdot}25$
Cu	$+0{\cdot}34$
Zn	$-0{\cdot}76$

Q.30 (a)1 mark

On what basis can we say that Cu is a transition element but Zn is not ? (Atomic number : Cu = 29, Zn = 30)

Q.30 (b)1 mark $Why do transition elements show variety of oxidation states ?$
Q.30 (c)2 marks $\mathrm{E^{o}_{M^{2+}/M}}$
OR
Q.30 (c) OR2 marks $\mathrm{d^4}$

Section E

5 marks each

Q.315 marks $(\Delta_{\mathrm{o}})$
Q.32 (a)5 marks $(\alpha)$
OR
Q.32 (b)5 marks $\mathrm{CH_3COCH_3}$
Q.33 (a)5 marks $0{\cdot}05$
OR
Q.33 (b)5 marks $0{\cdot}0025\ \mathrm{mol\,L^{-1}}$

Section A

1 mark each

Q.11 mark $\mathrm{SO_3^{2-}}$
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Q.21 mark $\mathrm{[Co(en)_3]^{3+}}$
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Q.31 mark $Which one of the following complexes is non-ionisable ?$
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Q.41 mark $Which of the following is a benzylic halide ?$
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Q.51 mark $Phenol is less acidic than :$
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Q.61 mark $\mathrm{(CH_3)_3\,C - O - CH_3}$
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Q.71 mark $Aspirin is formed by the acetylation of :$
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Q.81 mark $An azeotropic solution of two liquids has boiling point higher than either of them when it :$
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Q.91 mark $\mathrm{CuCl_2}$
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Q.101 mark $Half-life period of a first order reaction is 1386 seconds. The rate constant (k) of the reaction is :$
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Q.111 mark $0{\cdot}0225$
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Q.121 mark $2\mathrm{A} + \mathrm{B_2} \longrightarrow 2\mathrm{AB}$
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For Questions number 13 to 16, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below.
Q.131 mark $Assertion (A) : Aromatic primary amines can be prepared by Gabriel phthalimide synthesis. Reason (R) : Alkyl halide undergoes nucleophilic substitution with anion formed by phthalimide.$
Tap an option to check your answer.
Q.141 mark $Assertion (A) : Uracil base is present in RNA. Reason (R) : RNA undergoes self-replication.$
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Q.151 mark $Assertion (A) : Diazonium salts of aliphatic amines are more stable than those of aromatic amines. Reason (R) : Diazonium salts of aromatic amines show resonance.$
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Q.161 mark $(\mathrm{C_6H_5 - NHCOCH_3})$
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Section B

2 marks each

Q.172 marks $Define the following terms : (a) Essential amino acids (b) Nucleotide$
Q.182 marks $\mathrm{S_N1}$
Q.192 marks $1{\cdot}25 \times 10^{-3}\ \mathrm{s^{-1}}$
Q.20 (a)2 marks $What is lanthanoid contraction ? Actinoid contraction is greater from element to element than lanthanoid contraction. Why ?$
OR
Q.20 (b)2 marks $Why do transition metals have high enthalpy of atomization ? Which element of 3d-series has lowest enthalpy of atomization ?$
Q.212 marks $\mathrm{mol^{-1}}$

Section C

3 marks each

Q.223 marks $17\,^{\circ}\mathrm{C}$
Q.233 marks $\mathrm{Zn\,(s)} \mid \mathrm{Zn^{2+}}\ (0{\cdot}1\ \mathrm{M}) \parallel \mathrm{Sn^{2+}}\ (0{\cdot}001\ \mathrm{M}) \mid \mathrm{Sn\,(s)}$
Q.243 marks $The vapour pressure of a solvent at 283 K is 100 mm Hg. Calculate the vapour pressure of a dilute solution containing 1 mole of a strong electrolyte AB in 50 moles of the solvent at 283 K (assuming complete dissociation of solute AB).$
Q.253 marks $\mathrm{CH_3 - CH_2 - Br} \xrightarrow{\mathrm{KCN}} \mathrm{A} \xrightarrow[\text{Partial hydrolysis}]{\mathrm{OH^{-}}} \mathrm{B} \xrightarrow{\mathrm{NaOH} + \mathrm{Br_2}} \mathrm{C}$
Q.263 marks $Write the reaction involved in the following : (a) Wolff-Kishner reduction (b) Decarboxylation reaction (c) Cannizzaro reaction$
Q.273 marks $Give the equations of reactions for the preparation of : (any three) (a) Phenol from chlorobenzene (b) Salicylaldehyde from phenol (c) 2-Methoxyacetophenone from anisole (d) Picric acid from phenol$
Q.283 marks $Give reasons for the following : (a) Chlorine is ortho/para directing in electrophilic aromatic substitution reactions, though chlorine is an electron withdrawing group. (b) Racemic mixture is optically inactive. (c) Allyl chloride is hydrolysed more readily than n-propyl chloride.$

Section D

\mathrm{E^{o}_{M^{2+}/M}}

values shows the varying trends :

	$\mathrm{E^{o}_{M^{2+}/M}}$
V	$-1{\cdot}18$
Cr	$-0{\cdot}91$
Mn	$-1{\cdot}18$
Fe	$-0{\cdot}44$
Co	$-0{\cdot}28$
Ni	$-0{\cdot}25$
Cu	$+0{\cdot}34$
Zn	$-0{\cdot}76$

Q.29 (a)1 mark

On what basis can we say that Cu is a transition element but Zn is not ? (Atomic number : Cu = 29, Zn = 30)

Q.29 (b)1 mark $Why do transition elements show variety of oxidation states ?$
Q.29 (c)2 marks $\mathrm{E^{o}_{M^{2+}/M}}$
OR
Q.29 (c) OR2 marks $\mathrm{d^4}$
Carbohydrates are essential for life in both plants and animals. Carbohydrates are used as storage molecules as starch in plants and glycogen in animals. Chemically they are polyhydroxy aldehydes or ketones. On the basis of their behaviour on hydrolysis, carbohydrates are classified as monosaccharides, oligosaccharides and polysaccharides. All monosaccharides are reducing sugars, i.e., they are oxidized by Tollens' reagent and Fehling's solution. A monosaccharide like glucose is aldohexose and its molecular formula was found to be $\mathrm{C_6H_{12}O_6}$ . After reacting with different reagents like HI, $\mathrm{H_2N - OH}$ , Bromine water, $\mathrm{(CH_3CO)_2O}$ , etc. its structure was found to contain one aldehyde group, one primary alcoholic group, $(-\mathrm{CH_2OH})$ and four secondary alcoholic groups $(>\mathrm{CHOH})$ . Despite having the aldehyde group, glucose does not give some of the reactions of aldehyde group like Schiff's test, $\mathrm{NaHSO_3}$ addition. This explains the existence of glucose in two cyclic hemiacetal forms which differ only in the configuration of the hydroxyl group at C $-$ 1.
Q.30 (a)1 mark $What are reducing sugars ?$
Q.30 (b)1 mark $Classify the following into monosaccharide and disaccharide : Fructose, Sucrose, Lactose, Galactose$
Q.30 (c)2 marks $Name the polysaccharide which is known as 'animal starch'. Why is it called 'animal starch' ?$
OR
Q.30 (c) OR2 marks $-\mathrm{OH}$

Section E

5 marks each

Q.31 (a)5 marks $0{\cdot}05$
OR
Q.31 (b)5 marks $0{\cdot}0025\ \mathrm{mol\,L^{-1}}$
Q.325 marks $(\Delta_{\mathrm{o}})$
Q.33 (a)5 marks $(\alpha)$
OR
Q.33 (b)5 marks $\mathrm{CH_3COCH_3}$

Section A

1 mark each

Q.11 mark $The correct order for the increasing oxidizing power in 3d series of transition elements is :$
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Q.21 mark $\mathrm{[CoCl_2(en)_2]^{+}}$
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Q.31 mark $Which one of the following hybrid states is associated with low spin complex ?$
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Q.41 mark $Butanenitrile may be prepared by heating :$
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Q.51 mark $Which of the following is most acidic ?$
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Q.61 mark $\mathrm{(CH_3)_2\,CH - O - CH_3}$
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Q.71 mark $\mathrm{C_3H_8O}$
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Q.81 mark $On mixing 10 mL of acetone with 50 mL of chloroform, the total volume of the solution will be :$
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Q.91 mark $The unit of cell constant is :$
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Q.101 mark $\mathrm{R} \longrightarrow$
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Q.111 mark $\mathrm{A} \longrightarrow$
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Q.121 mark $0{\cdot}0225$
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For Questions number 13 to 16, two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below.
Q.131 mark $Assertion (A) : Aniline is a weaker base than cyclohexylamine. Reason (R) : Aniline is resonance stabilized.$
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Q.141 mark $Assertion (A) : Vitamin C cannot be stored in our body. Reason (R) : Vitamin C is water soluble and readily excreted in urine.$
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Q.151 mark $Assertion (A) : Ammonolysis of alkyl halides involves reaction between alkyl halide and ethanolic solution of ammonia. Reason (R) : Ammonolysis of alkyl halides mainly produces secondary amines.$
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Q.161 mark $Assertion (A) : Aniline does not undergo Friedel-Crafts reaction. Reason (R) : Friedel-Crafts reaction is a nucleophilic substitution reaction.$
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Section B

2 marks each

Q.172 marks $\mathrm{S_N1}$
Q.18 (a)2 marks $What is lanthanoid contraction ? Actinoid contraction is greater from element to element than lanthanoid contraction. Why ?$
OR
Q.18 (b)2 marks $Why do transition metals have high enthalpy of atomization ? Which element of 3d-series has lowest enthalpy of atomization ?$
Q.192 marks $Define the following terms : (a) Peptide linkage (b) Essential amino acids$
Q.202 marks $1{\cdot}25 \times 10^{-3}\ \mathrm{s^{-1}}$
Q.212 marks $\mathrm{mol^{-1}}$

Section C

3 marks each

Q.223 marks $Give the equations of reactions for the preparation of : (any three) (a) Phenol from chlorobenzene (b) Salicylaldehyde from phenol (c) 2-Methoxyacetophenone from anisole (d) Picric acid from phenol$
Q.233 marks $Give reasons for the following : (a) Chlorine is ortho/para directing in electrophilic aromatic substitution reactions, though chlorine is an electron withdrawing group. (b) Racemic mixture is optically inactive. (c) Allyl chloride is hydrolysed more readily than n-propyl chloride.$
Q.243 marks $The vapour pressure of a solvent at 283 K is 100 mm Hg. Calculate the vapour pressure of a dilute solution containing 1 mole of a strong electrolyte AB in 50 moles of the solvent at 283 K (assuming complete dissociation of solute AB).$
Q.253 marks $17\,^{\circ}\mathrm{C}$
Q.263 marks $\mathrm{Zn\,(s)} \mid \mathrm{Zn^{2+}}\ (0{\cdot}1\ \mathrm{M}) \parallel \mathrm{Sn^{2+}}\ (0{\cdot}001\ \mathrm{M}) \mid \mathrm{Sn\,(s)}$
Q.273 marks $\mathrm{CH_3 - CH_2 - Br} \xrightarrow{\mathrm{KCN}} \mathrm{A} \xrightarrow[\text{Partial hydrolysis}]{\mathrm{OH^{-}}} \mathrm{B} \xrightarrow{\mathrm{NaOH} + \mathrm{Br_2}} \mathrm{C}$
Q.283 marks $Write the reaction involved in the following : (a) Wolff-Kishner reduction (b) Decarboxylation reaction (c) Cannizzaro reaction$

Section D

Carbohydrates are essential for life in both plants and animals. Carbohydrates are used as storage molecules as starch in plants and glycogen in animals. Chemically they are polyhydroxy aldehydes or ketones. On the basis of their behaviour on hydrolysis, carbohydrates are classified as monosaccharides, oligosaccharides and polysaccharides. All monosaccharides are reducing sugars, i.e., they are oxidized by Tollens' reagent and Fehling's solution. A monosaccharide like glucose is aldohexose and its molecular formula was found to be $\mathrm{C_6H_{12}O_6}$ . After reacting with different reagents like HI, $\mathrm{H_2N - OH}$ , Bromine water, $\mathrm{(CH_3CO)_2O}$ , etc. its structure was found to contain one aldehyde group, one primary alcoholic group, $(-\mathrm{CH_2OH})$ and four secondary alcoholic groups $(>\mathrm{CHOH})$ . Despite having the aldehyde group, glucose does not give some of the reactions of aldehyde group like Schiff's test, $\mathrm{NaHSO_3}$ addition. This explains the existence of glucose in two cyclic hemiacetal forms which differ only in the configuration of the hydroxyl group at C $-$ 1.
Q.29 (a)1 mark $What are reducing sugars ?$
Q.29 (b)1 mark $Classify the following into monosaccharide and disaccharide : Fructose, Sucrose, Lactose, Galactose$
Q.29 (c)2 marks $Name the polysaccharide which is known as 'animal starch'. Why is it called 'animal starch' ?$
OR
Q.29 (c) OR2 marks $-\mathrm{OH}$

\mathrm{E^{o}_{M^{2+}/M}}

values shows the varying trends :

	$\mathrm{E^{o}_{M^{2+}/M}}$
V	$-1{\cdot}18$
Cr	$-0{\cdot}91$
Mn	$-1{\cdot}18$
Fe	$-0{\cdot}44$
Co	$-0{\cdot}28$
Ni	$-0{\cdot}25$
Cu	$+0{\cdot}34$
Zn	$-0{\cdot}76$

Q.30 (a)1 mark

On what basis can we say that Cu is a transition element but Zn is not ? (Atomic number : Cu = 29, Zn = 30)

Q.30 (b)1 mark $Why do transition elements show variety of oxidation states ?$
Q.30 (c)2 marks $\mathrm{E^{o}_{M^{2+}/M}}$
OR
Q.30 (c) OR2 marks $\mathrm{d^4}$

Section E

5 marks each

Q.31 (a)5 marks $(\alpha)$
OR
Q.31 (b)5 marks $\mathrm{CH_3COCH_3}$
Q.32 (a)5 marks $0{\cdot}05$
OR
Q.32 (b)5 marks $0{\cdot}0025\ \mathrm{mol\,L^{-1}}$
Q.335 marks $(\Delta_{\mathrm{o}})$