CBSE Class 12 Chemistry 2023 question paper (56/4)

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 $A compound undergoes complete tetramerization in a given organic solvent. The Van't Hoff factor 'i' is :$
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Q.21 mark $The half-life for a zero order reaction equals : where R is the initial concentration.$
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Q.31 mark $\alpha$
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Q.41 mark $The ions of metals of Group 12 (Zn, Cd and Hg) have completely filled d orbitals and so they :$
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Q.51 mark $\mathrm{[Co(NH_3)_5NO_3]SO_4}$
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Q.61 mark $Reaction of 1-phenyl-2-chloropropane with alcoholic KOH gives mainly :$
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Q.71 mark $When diethyl ether is heated with excess of HI, it produces :$
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Q.81 mark $The reduction of ethanenitrile with sodium and alcohol gives :$
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Q.91 mark $\mathrm{MnO_4^{-}}$
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Q.101 mark $In a reaction, the initial concentration of the reactants increases four fold and the rate becomes sixteen times its initial value. The order of the reaction is :$
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Q.111 mark $On hydrolysis, which of the following carbohydrates gives only glucose ?$
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Q.121 mark $Deficiency of which of the following vitamins causes Pernicious anaemia ?$
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Q.131 mark $\mathrm{C_6H_5CHO} + \mathrm{CH_3COCH_3} \xrightarrow[\Delta]{\mathrm{OH^{-}}} \mathrm{C_6H_5CH = CH - COCH_3}$
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Q.141 mark $In which of the following does the central atom exhibit an oxidation state of +3 ?$
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For Questions number 15 to 18, 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.151 mark $Assertion (A) : When NaCl is added to water, a depression in freezing point is observed. Reason (R) : The lowering of vapour pressure of a solution causes depression in the freezing point.$
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Q.161 mark $\Lambda_{\mathrm{m}}$
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Q.171 mark $Assertion (A) : Zr and Hf have almost identical radii. Reason (R) : Both Zr and Hf exhibit similar properties.$
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Q.181 mark $Assertion (A) : Monobromination of aniline can be conveniently done by protecting the amino group by acetylation. Reason (R) : Acetylation decreases the activating effect of the amino group.$
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Section B

2 marks each

Q.192 marks $\mathrm{C_6H_{13}Cl}$
Q.20 (a)2 marks $What type of deviation from Raoult's law is shown by a mixture of ethanol and acetone ? Give reason.$
OR
Q.20 (b)2 marks $Define Azeotrope. What type of azeotrope is formed by negative deviation from Raoult's law ? Give an example.$
Q.212 marks $Name the cell which : (a) was used in Apollo Space programme. (b) is used in automobiles and inverters. (c) is suitable for hearing aids and watches. (d) does not give a steady potential and is used in transistors.$
Q.222 marks $\mathrm{N_2O_5}$
Q.232 marks $\mathrm{CH_2 = CH_2} + \mathrm{H_2O} \xrightarrow{\mathrm{H^{+}}} \mathrm{CH_3CH_2OH}$
Q.24 (a)2 marks $\xrightarrow[\Delta]{\text{Conc. NaOH}}$
OR
Q.24 (b)2 marks $Do the following conversions in not more than two steps : (i) Toluene to Benzoic acid (ii) Benzaldehyde to 1-Phenylethanol$
Q.252 marks $\mathrm{[Co(NH_3)_4Cl(NO_2)]Cl}$

Section C

3 marks each

Q.26 (a)3 marks $+\ \mathrm{HBr} \longrightarrow$
OR
Q.26 (b)3 marks $\mathrm{HNO_3}$
Q.273 marks $\mathrm{S_N}1$
Q.283 marks $\mathrm{[Fe(CN)_6]^{3-}}$
Q.293 marks $\mathrm{mol^{-1}}$
Q.303 marks $\mathrm{C_2H_5Cl}$

Experiment	Time ( $\mathrm{s^{-1}}$ )	Total pressure (atm)
1	0	$0{\cdot}4$
2	100	$0{\cdot}6$

Section D

Living systems are made up of various complex biomolecules like carbohydrates, proteins, nucleic acids, lipids, etc. Carbohydrates are optically active polyhydroxy aldehydes or ketones or molecules which provide such units on hydrolysis. They are broadly classified into three groups — monosaccharides, oligosaccharides and polysaccharides. Monosaccharides are held together by glycosidic linkages to form disaccharides like sucrose, maltose or polysaccharides like starch and cellulose. Another biomolecule : proteins are polymers of $\alpha$ -amino acids which are linked by peptide bonds. Ten amino acids are called essential amino acids. Structure and shape of proteins can be studied at four different levels i.e. primary, secondary, tertiary and quaternary, each level being more complex than the previous one.
Q.31 (i)1 mark $What is the difference between a glycosidic linkage and peptide linkage ?$
Q.31 (ii)1 mark $Which amino acids are called essential amino acids ?$
Q.31 (iii) (a)2 marks $What are the common types of secondary structures of proteins ? Write any two forces which stabilise the secondary and tertiary structures of protein.$
OR
Q.31 (iii) (b)2 marks $Define denaturation of protein with an example. During denaturation which structures of protein lose their biological activity ?$
Amines are usually formed from nitro compounds, halides, amides, imides, etc. They exhibit hydrogen bonding which influences their physical properties. In alkyl amines, a combination of electron releasing, steric and hydrogen bonding factors influence the stability of the substituted ammonium cations in protic polar solvents and thus affect the basic nature of amines. In aromatic amines, electron releasing and withdrawing groups, respectively increase and decrease their basic character. Influence of the number of hydrogen atoms at nitrogen atom on the type of reactions and nature of products is responsible for identification and distinction between primary, secondary and tertiary amines. Presence of amino group in aromatic ring enhances reactivity of the aromatic amines. Aryl diazonium salts provide advantageous methods for producing aryl halides, cyanides, phenols and arenes by reductive removal of the diazo group.
Q.32 (i)1 mark $\mathrm{pK_b}$
Q.32 (ii)1 mark $Aniline on nitration gives a substantial amount of m-nitroaniline, though amino group is o/p directing. Why ?$
Q.32 (iii) (a)2 marks $\mathrm{C_7H_6O_2}$
OR
Q.32 (iii) (b)2 marks $+\ \mathrm{Br_2\,(aq)} \longrightarrow$

Section E

5 marks each

Q.33 (a)5 marks $\mathrm{Al\,(s)} \mid \mathrm{Al}^{3+}\,(0{\cdot}001\ \mathrm{M}) \parallel \mathrm{Ni}^{2+}\,(0{\cdot}1\ \mathrm{M}) \mid \mathrm{Ni\,(s)}$
OR
Q.33 (b)5 marks $\mathrm{NH_4^{+}}$
Q.34 (a)5 marks $\mathrm{Zn}^{2+}$
OR
Q.34 (b)5 marks $\mathrm{K_2Cr_2O_7}$
Q.355 marks $\alpha$

Section A

1 mark each

Q.11 mark $A compound undergoes complete dimerization in a given organic solvent. The Van't Hoff factor 'i' is :$
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Q.21 mark $\mathrm{A} + 2\mathrm{B} \longrightarrow \mathrm{C} + \mathrm{D}$
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Q.31 mark $Reaction of 1-phenyl-2-chloropropane with alcoholic KOH gives mainly :$
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Q.41 mark $The interstitial compounds of transition metals are than the metal itself.$
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Q.51 mark $\mathrm{[Co(NH_3)_6]\,[Cr(CN)_6]}$
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Q.61 mark $\alpha$
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Q.71 mark $\mathrm{C=O}$
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Q.81 mark $The action of nitrous acid on ethylamine gives mainly :$
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Q.91 mark $\mathrm{CuSO_4}$
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Q.101 mark $\frac{1}{4}$
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Q.111 mark $On hydrolysis, which of the following carbohydrates gives glucose and fructose ?$
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Q.121 mark $The deficiency of which of the following vitamins causes Scurvy ?$
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Q.131 mark $\mathrm{C_6H_5CH_3} \xrightarrow[\mathrm{2.\ H_3O^{+}}]{\mathrm{1.\ CrO_2Cl_2/CS_2}} \mathrm{C_6H_5CHO}$
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Q.141 mark $In which of the following does the central atom exhibit an oxidation state of +4 ?$
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For Questions number 15 to 18, 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.151 mark $Assertion (A) : When glucose is added to water, an elevation in boiling point is observed. Reason (R) : The lowering of vapour pressure causes elevation in the boiling point.$
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Q.161 mark $\Lambda_{\mathrm{m}}$
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Q.171 mark $Assertion (A) : Monobromination of aniline can be conveniently done by protecting the amino group by acetylation. Reason (R) : Acetylation decreases the activating effect of the amino group.$
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Q.181 mark $Assertion (A) : Manganese shows the highest oxidation state of +7 in 3d series. Reason (R) : Transition metals show variable oxidation states.$
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Section B

2 marks each

Q.19 (a)2 marks $What type of deviation from Raoult's law is shown by a mixture of ethanol and acetone ? Give reason.$
OR
Q.19 (b)2 marks $Define Azeotrope. What type of azeotrope is formed by negative deviation from Raoult's law ? Give an example.$
Q.202 marks $\mathrm{C_6H_{13}Cl}$
Q.212 marks $\mathrm{N_2O_5}$
Q.222 marks $Name the cell which : (a) was used in Apollo Space programme. (b) is used in automobiles and inverters. (c) is suitable for hearing aids and watches. (d) does not give a steady potential and is used in transistors.$
Q.232 marks $\mathrm{[Cr(NH_3)_3(H_2O)_3]Cl_3}$
Q.242 marks $+\ \mathrm{CH_3Br}$
Q.25 (a)2 marks $\xrightarrow[\Delta]{\text{Conc. NaOH}}$
OR
Q.25 (b)2 marks $Do the following conversions in not more than two steps : (i) Toluene to Benzoic acid (ii) Benzaldehyde to 1-Phenylethanol$

Section C

3 marks each

Q.263 marks $\mathrm{C_2H_5Cl}$
Q.273 marks $\mathrm{mol^{-1}}$
Q.283 marks $\mathrm{[Fe(CN)_6]^{3-}}$
Q.293 marks $\mathrm{S_N}1$
Q.30 (a)3 marks $+\ \mathrm{HBr} \longrightarrow$
OR
Q.30 (b)3 marks $\mathrm{HNO_3}$

Experiment	Time ( $\mathrm{s^{-1}}$ )	Total pressure (atm)
1	0	$0{\cdot}4$
2	100	$0{\cdot}6$

Section D

Amines are usually formed from nitro compounds, halides, amides, imides, etc. They exhibit hydrogen bonding which influences their physical properties. In alkyl amines, a combination of electron releasing, steric and hydrogen bonding factors influence the stability of the substituted ammonium cations in protic polar solvents and thus affect the basic nature of amines. In aromatic amines, electron releasing and withdrawing groups, respectively increase and decrease their basic character. Influence of the number of hydrogen atoms at nitrogen atom on the type of reactions and nature of products is responsible for identification and distinction between primary, secondary and tertiary amines. Presence of amino group in aromatic ring enhances reactivity of the aromatic amines. Aryl diazonium salts provide advantageous methods for producing aryl halides, cyanides, phenols and arenes by reductive removal of the diazo group.
Q.31 (i)1 mark $\mathrm{pK_b}$
Q.31 (ii)1 mark $Aniline on nitration gives a substantial amount of m-nitroaniline, though amino group is o/p directing. Why ?$
Q.31 (iii) (a)2 marks $\mathrm{C_7H_6O_2}$
OR
Q.31 (iii) (b)2 marks $+\ \mathrm{Br_2\,(aq)} \longrightarrow$
Living systems are made up of various complex biomolecules like carbohydrates, proteins, nucleic acids, lipids, etc. Carbohydrates are optically active polyhydroxy aldehydes or ketones or molecules which provide such units on hydrolysis. They are broadly classified into three groups — monosaccharides, oligosaccharides and polysaccharides. Monosaccharides are held together by glycosidic linkages to form disaccharides like sucrose, maltose or polysaccharides like starch and cellulose. Another biomolecule : proteins are polymers of $\alpha$ -amino acids which are linked by peptide bonds. Ten amino acids are called essential amino acids. Structure and shape of proteins can be studied at four different levels i.e. primary, secondary, tertiary and quaternary, each level being more complex than the previous one.
Q.32 (i)1 mark $What is the difference between a glycosidic linkage and peptide linkage ?$
Q.32 (ii)1 mark $Which amino acids are called essential amino acids ?$
Q.32 (iii) (a)2 marks $What are the common types of secondary structures of proteins ? Write any two forces which stabilise the secondary and tertiary structures of protein.$
OR
Q.32 (iii) (b)2 marks $Define denaturation of protein with an example. During denaturation which structures of protein lose their biological activity ?$

Section E

5 marks each

Q.335 marks $\alpha$
Q.34 (a)5 marks $\mathrm{Al\,(s)} \mid \mathrm{Al}^{3+}\,(0{\cdot}001\ \mathrm{M}) \parallel \mathrm{Ni}^{2+}\,(0{\cdot}1\ \mathrm{M}) \mid \mathrm{Ni\,(s)}$
OR
Q.34 (b)5 marks $\mathrm{NH_4^{+}}$
Q.35 (a)5 marks $\mathrm{Zn}^{2+}$
OR
Q.35 (b)5 marks $\mathrm{K_2Cr_2O_7}$

Section A

1 mark each

Q.11 mark $\mathrm{CaCl_2 \cdot 6H_2O}$
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Q.21 mark $\mathrm{A} \rightarrow$
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Q.31 mark $\mathrm{Cu^{2+}}$
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Q.41 mark $\alpha$
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Q.51 mark $\mathrm{[Cr(H_2O)_6]Cl_3}$
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Q.61 mark $Which of the following alkenes on acid catalysed hydration gives a tertiary alcohol ?$
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Q.71 mark $When nitrobenzene is heated with tin and concentrated HCl, the product formed is :$
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Q.81 mark $Reaction of 1-phenyl-2-chloropropane with alcoholic KOH gives mainly :$
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Q.91 mark $Corrosion of iron is :$
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Q.101 mark $The number of molecules that react with each other in an elementary reaction is a measure of the :$
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Q.111 mark $On hydrolysis, which of the following carbohydrates gives glucose and galactose ?$
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Q.121 mark $The deficiency of which of the following vitamins causes 'Rickets' ?$
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Q.131 mark $Which of the following is an 'Acetal' ?$
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Q.141 mark $(\Delta_{\mathrm{t}})$
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For Questions number 15 to 18, 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.151 mark $Assertion (A) : When NaCl is added to water, a depression in freezing point is observed. Reason (R) : The vapour pressure of solution is increased which causes depression in freezing point.$
Tap an option to check your answer.
Q.161 mark $Assertion (A) : Monobromination of aniline can be conveniently done by protecting the amino group by acetylation. Reason (R) : Acetylation decreases the activating effect of the amino group.$
Tap an option to check your answer.
Q.171 mark $(\Lambda^{\circ}_{\mathrm{m}})$
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Q.181 mark $\mathrm{E}^{\circ}_{\mathrm{Cu}^{2+}/\mathrm{Cu}}$
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Section B

2 marks each

Q.192 marks $\mathrm{[Co(en)_2(H_2O)(CN)]^{2+}}$
Q.202 marks $Name the cell which : (a) was used in Apollo Space programme. (b) is used in automobiles and inverters. (c) is suitable for hearing aids and watches. (d) does not give a steady potential and is used in transistors.$
Q.21 (a)2 marks $What type of deviation from Raoult's law is shown by a mixture of ethanol and acetone ? Give reason.$
OR
Q.21 (b)2 marks $Define Azeotrope. What type of azeotrope is formed by negative deviation from Raoult's law ? Give an example.$
Q.22 (a)2 marks $\xrightarrow[\Delta]{\text{Conc. NaOH}}$
OR
Q.22 (b)2 marks $Do the following conversions in not more than two steps : (i) Toluene to Benzoic acid (ii) Benzaldehyde to 1-Phenylethanol$
Q.232 marks $\mathrm{N_2O_5}$
Q.242 marks $\mathrm{C_6H_{13}Cl}$
Q.252 marks $Write the mechanism of acid dehydration of ethanol to yield ethene.$

Section C

3 marks each

Q.263 marks $\mathrm{S_N}1$
Q.273 marks $\mathrm{C_2H_5Cl}$
Q.283 marks $\mathrm{mol^{-1}}$
Q.29 (a)3 marks $+\ \mathrm{HBr} \longrightarrow$
OR
Q.29 (b)3 marks $\mathrm{HNO_3}$
Q.303 marks $\mathrm{[Fe(CN)_6]^{3-}}$

Experiment	Time ( $\mathrm{s^{-1}}$ )	Total pressure (atm)
1	0	$0{\cdot}4$
2	100	$0{\cdot}6$

Section D

Living systems are made up of various complex biomolecules like carbohydrates, proteins, nucleic acids, lipids, etc. Carbohydrates are optically active polyhydroxy aldehydes or ketones or molecules which provide such units on hydrolysis. They are broadly classified into three groups — monosaccharides, oligosaccharides and polysaccharides. Monosaccharides are held together by glycosidic linkages to form disaccharides like sucrose, maltose or polysaccharides like starch and cellulose. Another biomolecule : proteins are polymers of $\alpha$ -amino acids which are linked by peptide bonds. Ten amino acids are called essential amino acids. Structure and shape of proteins can be studied at four different levels i.e. primary, secondary, tertiary and quaternary, each level being more complex than the previous one.
Q.31 (i)1 mark $What is the difference between a glycosidic linkage and peptide linkage ?$
Q.31 (ii)1 mark $Which amino acids are called essential amino acids ?$
Q.31 (iii) (a)2 marks $What are the common types of secondary structures of proteins ? Write any two forces which stabilise the secondary and tertiary structures of protein.$
OR
Q.31 (iii) (b)2 marks $Define denaturation of protein with an example. During denaturation which structures of protein lose their biological activity ?$
Amines are usually formed from nitro compounds, halides, amides, imides, etc. They exhibit hydrogen bonding which influences their physical properties. In alkyl amines, a combination of electron releasing, steric and hydrogen bonding factors influence the stability of the substituted ammonium cations in protic polar solvents and thus affect the basic nature of amines. In aromatic amines, electron releasing and withdrawing groups, respectively increase and decrease their basic character. Influence of the number of hydrogen atoms at nitrogen atom on the type of reactions and nature of products is responsible for identification and distinction between primary, secondary and tertiary amines. Presence of amino group in aromatic ring enhances reactivity of the aromatic amines. Aryl diazonium salts provide advantageous methods for producing aryl halides, cyanides, phenols and arenes by reductive removal of the diazo group.
Q.32 (i)1 mark $\mathrm{pK_b}$
Q.32 (ii)1 mark $Aniline on nitration gives a substantial amount of m-nitroaniline, though amino group is o/p directing. Why ?$
Q.32 (iii) (a)2 marks $\mathrm{C_7H_6O_2}$
OR
Q.32 (iii) (b)2 marks $+\ \mathrm{Br_2\,(aq)} \longrightarrow$

Section E

5 marks each

Q.33 (a)5 marks $\mathrm{Zn}^{2+}$
OR
Q.33 (b)5 marks $\mathrm{K_2Cr_2O_7}$
Q.345 marks $\alpha$
Q.35 (a)5 marks $\mathrm{Al\,(s)} \mid \mathrm{Al}^{3+}\,(0{\cdot}001\ \mathrm{M}) \parallel \mathrm{Ni}^{2+}\,(0{\cdot}1\ \mathrm{M}) \mid \mathrm{Ni\,(s)}$
OR
Q.35 (b)5 marks $\mathrm{NH_4^{+}}$