CBSE Class 12 Chemistry 2023 question paper (56/3)

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 $Which of the following is not true about enantiomers ?$
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Q.21 mark $Aspirin is obtained by the acetylation of which of the following compounds ?$
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Q.31 mark $\mathrm{HCHO}$
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Q.41 mark $Among the following, which is the strongest base ?$
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Q.51 mark $On hydrolysis, which of the following carbohydrates gives only glucose ?$
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Q.61 mark $Which of the following vitamins is water soluble ?$
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Q.71 mark $The unit of the rate of reaction is the same as that of the rate constant for a :$
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Q.81 mark $\Lambda = \Lambda_{o} - \mathrm{A}\sqrt{\mathrm{C}}$
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Q.91 mark $An azeotropic mixture of two liquids has a boiling point higher than either of the two liquids when it :$
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Q.101 mark $Which of the following colligative property is used to find the molar mass of proteins ?$
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Q.111 mark $Among the following outermost configurations of transition metals which one shows the highest oxidation state ?$
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Q.121 mark $\mathrm{[Ni(NH_3)_6]Cl_2}$
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Q.131 mark $Which of the following species is not expected to be a ligand ?$
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Q.141 mark $Which of the following is the most stable complex species ?$
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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 $Assertion (A) : Order and molecularity of a reaction are always same. Reason (R) : Complex reactions involve a sequence of elementary reactions and the slowest step is rate determining.$
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Q.161 mark $\mathrm{NaCl}$
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Q.171 mark $\mathrm{C-Cl}$
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Q.181 mark $Assertion (A): Zinc is not regarded as a transition element. Reason (R): In zinc, 3d orbitals are completely filled in its ground state as well as in its oxidised state.$
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Section B

2 marks each

Q.192 marks $\mathrm{(CH_3)_2CHMgBr}$
Q.202 marks $2\mathrm{N_2O_5\,(g)} \longrightarrow 4\mathrm{NO_2\,(g)} + \mathrm{O_2\,(g)}$
Q.21 (a)2 marks $Define fuel cell and write its two advantages.$
OR
Q.21 (b)2 marks $\mathrm{E}^{\circ}$
Q.22 (a)2 marks $(i) How are carbohydrates stored in animal body ? Mention any one organ where they are present. (ii) What is the basic structural difference between starch and cellulose ?$
OR
Q.22 (b)2 marks $Differentiate between : (i) Peptide linkage and Glycosidic linkage (ii) Nucleoside and Nucleotide$
Q.232 marks $\mathrm{HCN}$
Q.242 marks $Write the chemical equation involved in the following reactions : (a) Carbylamine reaction (b) Gabriel phthalimide synthesis$
Q.252 marks $Give reasons for the following : (a) Aquatic animals are more comfortable in cold water in comparison to warm water. (b) Sprinkling of salt helps in clearing the snow-covered roads in hilly areas.$

Section C

3 marks each

Q.263 marks $\mathrm{CH_3 - CH_2 - OH} \xrightarrow[443\ \mathrm{K}]{\mathrm{H}^{+}} \mathrm{CH_2 = CH_2} + \mathrm{H_2O}$
Q.27 (a)3 marks $\mathrm{C_6H_5-COOH} \xrightarrow[\Delta]{\mathrm{NH_3}} \mathrm{A} \xrightarrow{\mathrm{Br_2 + NaOH}} \mathrm{B} \xrightarrow[0^{\circ}\mathrm{C}]{\mathrm{NaNO_2 + HCl}} \mathrm{C}$
OR
Q.27 (b)3 marks $How will you convert the following : (i) Aniline to p-bromoaniline (ii) Ethanoic acid to methanamine (iii) Butanenitrile to 1-aminobutane$
Q.283 marks $0{\cdot}3$
Q.293 marks $27^{\circ}\mathrm{C}$
Q.303 marks $\mathrm{HI}$

Section D

The polarity of $\mathrm{C - X}$ bond of alkyl halides is responsible for their nucleophilic substitution, elimination and their reaction with metal atoms to form organometallic compounds. Alkyl halides are prepared by the free radical halogenation of alkanes, addition of halogen acids to alkenes, replacement of $-\mathrm{OH}$ group of alcohols with halogens using phosphorus halides, thionyl chloride or halogen acids. Aryl halides are prepared by electrophilic substitution of arenes. Nucleophilic substitution reactions are categorised into $\mathrm{S_N^{1}}$ and $\mathrm{S_N^{2}}$ on the basis of their kinetic properties. Chirality has a profound role in understanding the $\mathrm{S_N^{1}}$ and $\mathrm{S_N^{2}}$ mechanism.
Q.31 (i)1 mark $\mathrm{Mg}$
Q.31 (ii)1 mark $\mathrm{S_N^{1}}$
Q.31 (iii) (a)2 marks $Write the equations for the preparation of 1-iodobutane from (1) 1-chlorobutane (2) but-1-ene.$
OR
Q.31 (iii) (b)2 marks $\mathrm{CH_3 - CH(Br) - CH_3} + \mathrm{KOH} \xrightarrow[\text{heat}]{\text{Ethanol}}$
Coordination compounds are widely present in the minerals, plant and animal worlds and are known to play many important functions in the area of analytical chemistry, metallurgy, biological systems and medicine. Alfred Werner's theory postulated the use of two types of linkages (primary and secondary), by a metal atom/ion in a coordination compound. He predicted the geometrical shapes of a large number of coordination entities using the property of isomerism. The Valence Bond Theory (VBT) explains the formation, magnetic behaviour and geometrical shapes of coordination compounds. It, however, fails to describe the optical properties of these compounds. The Crystal Field Theory (CFT) explains the effect of different crystal fields (provided by the ligands taken as point charges) on the degeneracy of d-orbital energies of the central metal atom/ion.
Q.32 (i)1 mark $\mathrm{NiCl_2 \cdot 6H_2O}$
Q.32 (ii)1 mark $\mathrm{[Co(NH_3)_5(SO_4)]Cl}$
Q.32 (iii) (a)2 marks $\mathrm{[Ni(CO)_4]}$
OR
Q.32 (iii) (b)2 marks $\mathrm{[Co(NH_3)_6]^{3+}}$

Section E

5 marks each

Q.33 (a)5 marks $\mathrm{E}^{\circ}_{\mathrm{Mn}^{2+}/\mathrm{Mn}}$
OR
Q.33 (b)5 marks $\mathrm{Cr_2O_7^{2-}} + 14\mathrm{H}^{+} + 6\mathrm{Fe}^{2+} \longrightarrow$
Q.34 (a)5 marks $\mathrm{C_5H_{10}O}$
OR
Q.34 (b)5 marks $\mathrm{O_2N - CH_2 - COOH}$
Q.355 marks $25^{\circ}\mathrm{C}$

Section A

1 mark each

Q.11 mark $Which of the following has the highest melting point ?$
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Q.21 mark $\mathrm{CO_2}$
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Q.31 mark $\mathrm{C_5H_{10}O}$
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Q.41 mark $Benzene diazonium chloride on hydrolysis gives :$
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Q.51 mark $Helical structure of proteins is stabilized by :$
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Q.61 mark $A vitamin which plays a vital role in the clotting of blood is :$
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Q.71 mark $\mathrm{A} + \mathrm{B} \longrightarrow \text{Products}$
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Q.81 mark $An azeotropic mixture of two liquids has a boiling point higher than either of the two liquids when it :$
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Q.91 mark $\Lambda = \Lambda_{o} - \mathrm{A}\sqrt{\mathrm{C}}$
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Q.101 mark $Isotonic solutions have :$
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Q.111 mark $\mathrm{KMnO_4}$
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Q.121 mark $Which of the following transition metals does not show variable oxidation state ?$
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Q.131 mark $Which of the following complexes is a 'chelate' complex ?$
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Q.141 mark $Optical isomerism is not shown by the complex :$
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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 $Assertion (A): Zinc is not regarded as a transition element. Reason (R): In zinc, 3d orbitals are completely filled in its ground state as well as in its oxidised state.$
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Q.161 mark $\mathrm{C-Cl}$
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Q.171 mark $\mathrm{NaCl}$
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Q.181 mark $Assertion (A) : Order and molecularity of a reaction are always same. Reason (R) : Complex reactions involve a sequence of elementary reactions and the slowest step is rate determining.$
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Section B

2 marks each

Q.192 marks $Show how you will synthesise : (a) 1-Methylcyclohexan-1-ol from a suitable alkene. (b) Cyclohexylmethanol from methanal using a suitable Grignard reagent.$
Q.202 marks $Write the chemical equation involved in the following reactions : (a) Carbylamine reaction (b) Gabriel phthalimide synthesis$
Q.21 (a)2 marks $(i) How are carbohydrates stored in animal body ? Mention any one organ where they are present. (ii) What is the basic structural difference between starch and cellulose ?$
OR
Q.21 (b)2 marks $Differentiate between : (i) Peptide linkage and Glycosidic linkage (ii) Nucleoside and Nucleotide$
Q.22 (a)2 marks $Define fuel cell and write its two advantages.$
OR
Q.22 (b)2 marks $\mathrm{E}^{\circ}$
Q.232 marks $On mixing liquid X and liquid Y, volume of the resulting solution decreases. What type of deviation from Raoult's law is shown by the resulting solution ? What change in temperature would you observe after mixing liquids X and Y ?$

Q.242 marks

2\mathrm{NO_2\,(g)} + \mathrm{F_2\,(g)} \longrightarrow 2\mathrm{NO_2F\,(g)}

Q.252 marks $\mathrm{HCN}$

Experiment No.	$[\mathrm{NO_2}]/\mathrm{M}$	$[\mathrm{F_2}]/\mathrm{M}$	Initial rate $\mathrm{M\ min^{-1}}$
1	$0{\cdot}2$	$0{\cdot}05$	$6 \times 10^{-3}$
2	$0{\cdot}4$	$0{\cdot}05$	$1{\cdot}2 \times 10^{-2}$
3	$0{\cdot}8$	$0{\cdot}10$	$4{\cdot}8 \times 10^{-2}$

Section C

3 marks each

Q.263 marks $\mathrm{CH_2 = CH_2} + \mathrm{H_2O} \xrightarrow{\mathrm{H}^{+}} \mathrm{CH_3CH_2OH}$
Q.273 marks $\mathrm{HI}$
Q.283 marks $27^{\circ}\mathrm{C}$
Q.293 marks $0{\cdot}3$
Q.30 (a)3 marks $\mathrm{C_6H_5-COOH} \xrightarrow[\Delta]{\mathrm{NH_3}} \mathrm{A} \xrightarrow{\mathrm{Br_2 + NaOH}} \mathrm{B} \xrightarrow[0^{\circ}\mathrm{C}]{\mathrm{NaNO_2 + HCl}} \mathrm{C}$
OR
Q.30 (b)3 marks $How will you convert the following : (i) Aniline to p-bromoaniline (ii) Ethanoic acid to methanamine (iii) Butanenitrile to 1-aminobutane$

Section D

Coordination compounds are widely present in the minerals, plant and animal worlds and are known to play many important functions in the area of analytical chemistry, metallurgy, biological systems and medicine. Alfred Werner's theory postulated the use of two types of linkages (primary and secondary), by a metal atom/ion in a coordination compound. He predicted the geometrical shapes of a large number of coordination entities using the property of isomerism. The Valence Bond Theory (VBT) explains the formation, magnetic behaviour and geometrical shapes of coordination compounds. It, however, fails to describe the optical properties of these compounds. The Crystal Field Theory (CFT) explains the effect of different crystal fields (provided by the ligands taken as point charges) on the degeneracy of d-orbital energies of the central metal atom/ion.
Q.31 (i)1 mark $\mathrm{NiCl_2 \cdot 6H_2O}$
Q.31 (ii)1 mark $\mathrm{[Co(NH_3)_5(SO_4)]Cl}$
Q.31 (iii) (a)2 marks $\mathrm{[Ni(CO)_4]}$
OR
Q.31 (iii) (b)2 marks $\mathrm{[Co(NH_3)_6]^{3+}}$
The polarity of $\mathrm{C - X}$ bond of alkyl halides is responsible for their nucleophilic substitution, elimination and their reaction with metal atoms to form organometallic compounds. Alkyl halides are prepared by the free radical halogenation of alkanes, addition of halogen acids to alkenes, replacement of $-\mathrm{OH}$ group of alcohols with halogens using phosphorus halides, thionyl chloride or halogen acids. Aryl halides are prepared by electrophilic substitution of arenes. Nucleophilic substitution reactions are categorised into $\mathrm{S_N^{1}}$ and $\mathrm{S_N^{2}}$ on the basis of their kinetic properties. Chirality has a profound role in understanding the $\mathrm{S_N^{1}}$ and $\mathrm{S_N^{2}}$ mechanism.
Q.32 (i)1 mark $\mathrm{Mg}$
Q.32 (ii)1 mark $\mathrm{S_N^{1}}$
Q.32 (iii) (a)2 marks $Write the equations for the preparation of 1-iodobutane from (1) 1-chlorobutane (2) but-1-ene.$
OR
Q.32 (iii) (b)2 marks $\mathrm{CH_3 - CH(Br) - CH_3} + \mathrm{KOH} \xrightarrow[\text{heat}]{\text{Ethanol}}$

Section E

5 marks each

Q.335 marks $25^{\circ}\mathrm{C}$
Q.34 (a)5 marks $\mathrm{E}^{\circ}_{\mathrm{Mn}^{2+}/\mathrm{Mn}}$
OR
Q.34 (b)5 marks $\mathrm{Cr_2O_7^{2-}} + 14\mathrm{H}^{+} + 6\mathrm{Fe}^{2+} \longrightarrow$
Q.35 (a)5 marks $\mathrm{C_5H_{10}O}$
OR
Q.35 (b)5 marks $\mathrm{O_2N - CH_2 - COOH}$

Section A

1 mark each

Q.11 mark $\Lambda = \Lambda_{o} - \mathrm{A}\sqrt{\mathrm{C}}$
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Q.21 mark $Which of the following belongs to the class of alkyl halides ?$
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Q.31 mark $An azeotropic mixture of two liquids has a boiling point higher than either of the two liquids when it :$
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Q.41 mark $For the conversion of propene into 1-propanol, which of the following reagents and conditions should be used ?$
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Q.51 mark $\mathrm{CH_3COCl}$
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Q.61 mark $The reaction of ammonia with a large excess of methyl chloride will yield mainly :$
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Q.71 mark $In the ring structure of glucose, the anomeric carbon is :$
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Q.81 mark $Deficiency of Vitamin B causes :$
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Q.91 mark $The cathode reaction during the charging of a lead storage battery leads to the :$
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Q.101 mark $Which one of the following pairs will not form an ideal solution ?$
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Q.111 mark $The half-life of a reaction is doubled when the initial concentration is doubled. The order of the reaction is :$
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Q.121 mark $Which of the following ions has the maximum number of unpaired d-electrons ? [Atomic number : Fe = 26, V = 23, Ti = 22, Sc = 21]$
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Q.131 mark $Which of the following is a polydentate ligand ?$
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Q.141 mark $Which of the following coordination compounds exhibits linkage isomerism ?$
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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 $\mathrm{C-Cl}$
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Q.161 mark $Assertion (A) : Order and molecularity of a reaction are always same. Reason (R) : Complex reactions involve a sequence of elementary reactions and the slowest step is rate determining.$
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Q.171 mark $Assertion (A): Zinc is not regarded as a transition element. Reason (R): In zinc, 3d orbitals are completely filled in its ground state as well as in its oxidised state.$
Tap an option to check your answer.
Q.181 mark $\mathrm{Fe^{2+}}$
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Section B

2 marks each

Q.192 marks $\mathrm{C_6H_{11}MgBr}$
Q.202 marks $0{\cdot}3010$
Q.212 marks $Write the chemical equation involved in the following reactions : (a) Carbylamine reaction (b) Gabriel phthalimide synthesis$
Q.222 marks $What type of deviation from Raoult's law is shown by a mixture of ethanol and acetone ? Give reason.$
Q.23 (a)2 marks $(i) How are carbohydrates stored in animal body ? Mention any one organ where they are present. (ii) What is the basic structural difference between starch and cellulose ?$
OR
Q.23 (b)2 marks $Differentiate between : (i) Peptide linkage and Glycosidic linkage (ii) Nucleoside and Nucleotide$
Q.24 (a)2 marks $Define fuel cell and write its two advantages.$
OR
Q.24 (b)2 marks $\mathrm{E}^{\circ}$
Q.252 marks $(\alpha)$

Section C

3 marks each

Q.263 marks $27^{\circ}\mathrm{C}$
Q.273 marks $\mathrm{HI}$
Q.28 (a)3 marks $\mathrm{C_6H_5-COOH} \xrightarrow[\Delta]{\mathrm{NH_3}} \mathrm{A} \xrightarrow{\mathrm{Br_2 + NaOH}} \mathrm{B} \xrightarrow[0^{\circ}\mathrm{C}]{\mathrm{NaNO_2 + HCl}} \mathrm{C}$
OR
Q.28 (b)3 marks $How will you convert the following : (i) Aniline to p-bromoaniline (ii) Ethanoic acid to methanamine (iii) Butanenitrile to 1-aminobutane$
Q.293 marks $0{\cdot}3$
Q.303 marks $\mathrm{CH_3 - CH_2 - OH} \xrightarrow[443\ \mathrm{K}]{\mathrm{H}^{+}} \mathrm{CH_2 = CH_2} + \mathrm{H_2O}$

Section D

The polarity of $\mathrm{C - X}$ bond of alkyl halides is responsible for their nucleophilic substitution, elimination and their reaction with metal atoms to form organometallic compounds. Alkyl halides are prepared by the free radical halogenation of alkanes, addition of halogen acids to alkenes, replacement of $-\mathrm{OH}$ group of alcohols with halogens using phosphorus halides, thionyl chloride or halogen acids. Aryl halides are prepared by electrophilic substitution of arenes. Nucleophilic substitution reactions are categorised into $\mathrm{S_N^{1}}$ and $\mathrm{S_N^{2}}$ on the basis of their kinetic properties. Chirality has a profound role in understanding the $\mathrm{S_N^{1}}$ and $\mathrm{S_N^{2}}$ mechanism.
Q.31 (i)1 mark $\mathrm{Mg}$
Q.31 (ii)1 mark $\mathrm{S_N^{1}}$
Q.31 (iii) (a)2 marks $Write the equations for the preparation of 1-iodobutane from (1) 1-chlorobutane (2) but-1-ene.$
OR
Q.31 (iii) (b)2 marks $\mathrm{CH_3 - CH(Br) - CH_3} + \mathrm{KOH} \xrightarrow[\text{heat}]{\text{Ethanol}}$
Coordination compounds are widely present in the minerals, plant and animal worlds and are known to play many important functions in the area of analytical chemistry, metallurgy, biological systems and medicine. Alfred Werner's theory postulated the use of two types of linkages (primary and secondary), by a metal atom/ion in a coordination compound. He predicted the geometrical shapes of a large number of coordination entities using the property of isomerism. The Valence Bond Theory (VBT) explains the formation, magnetic behaviour and geometrical shapes of coordination compounds. It, however, fails to describe the optical properties of these compounds. The Crystal Field Theory (CFT) explains the effect of different crystal fields (provided by the ligands taken as point charges) on the degeneracy of d-orbital energies of the central metal atom/ion.
Q.32 (i)1 mark $\mathrm{NiCl_2 \cdot 6H_2O}$
Q.32 (ii)1 mark $\mathrm{[Co(NH_3)_5(SO_4)]Cl}$
Q.32 (iii) (a)2 marks $\mathrm{[Ni(CO)_4]}$
OR
Q.32 (iii) (b)2 marks $\mathrm{[Co(NH_3)_6]^{3+}}$

Section E

5 marks each

Q.33 (a)5 marks $\mathrm{C_5H_{10}O}$
OR
Q.33 (b)5 marks $\mathrm{O_2N - CH_2 - COOH}$
Q.345 marks $25^{\circ}\mathrm{C}$
Q.35 (a)5 marks $\mathrm{E}^{\circ}_{\mathrm{Mn}^{2+}/\mathrm{Mn}}$
OR
Q.35 (b)5 marks $\mathrm{Cr_2O_7^{2-}} + 14\mathrm{H}^{+} + 6\mathrm{Fe}^{2+} \longrightarrow$