CBSE Class 12 Chemistry 2024 question paper (56/1)

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 $Which one of the following first row transition elements is expected to have the highest third ionization enthalpy ?$
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Q.21 mark $\mathrm{(CrO_3)}$
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Q.31 mark $\beta$
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Q.41 mark $For an electrolyte undergoing association in a solvent, the van't Hoff factor :$
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Q.51 mark $\mathrm{X} + 2\mathrm{Y} \rightarrow \mathrm{P}$
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Q.61 mark $\mathrm{S_N1}$
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Q.71 mark $\mathrm{PCl_5}$
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Q.81 mark $The formation of cyanohydrin from an aldehyde is an example of :$
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Q.91 mark $In the Arrhenius equation, when log k is plotted against 1/T, a straight line is obtained whose :$
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Q.101 mark $The reaction of an alkyl halide with sodium alkoxide forming ether is known as :$
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Q.111 mark $\mathrm{H_2SO_4}$
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Q.121 mark $Which functional groups of glucose interact to form cyclic hemiacetal leading to pyranose structure ?$
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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 $Assertion (A) : When NaCl is added to water a depression in freezing point is observed. Reason (R) : NaCl undergoes dissociation in water.$
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Q.141 mark $Assertion (A) : Separation of Zr and Hf is difficult. Reason (R) : Zr and Hf have similar radii due to lanthanoid contraction.$
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Q.151 mark $\mathrm{pK_a}$
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Q.161 mark $Assertion (A) : Aniline is a stronger base than ammonia. Reason (R) : The unshared electron pair on nitrogen atom in aniline becomes less available for protonation due to resonance.$
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Section B

2 marks each

Q.172 marks $\mathrm{Fe^{2+}}$
Q.182 marks $Define molecularity of the reaction. State any one condition in which a bimolecular reaction may be kinetically of first order.$
Q.192 marks $\mathrm{HNO_3}$
Q.20 (a)2 marks $\mathrm{C_6H_5-CH=CH_2} + \mathrm{HBr} \longrightarrow$
OR
Q.20 (b)2 marks $Give reasons for the following : (i) Grignard reagent should be prepared under anhydrous conditions. (ii) Alkyl halides give alcohol with aqueous KOH whereas in the presence of alcoholic KOH, alkenes are formed.$
Q.212 marks $Write the chemical equation when : (a) Butan-2-one is treated with Zn(Hg) and conc. HCl. (b) Two molecules of benzaldehyde are treated with conc. NaOH.$

Section C

3 marks each

Q.223 marks $0{\cdot}05$

Q.233 marks

2\mathrm{NO\,(g)} + \mathrm{Br_2\,(g)} \rightarrow 2\mathrm{NOBr\,(g)}

Q.243 marks $\mathrm{[Cr(NH_3)_5Cl]Cl_2}$
Q.253 marks $\mathrm{CH_3-CH=CH-Br}$
Q.263 marks $\mathrm{CH_3CH_2OH} \xrightarrow[443\ \mathrm{K}]{\mathrm{H^+}} \mathrm{CH_2=CH_2}$
Q.273 marks $Answer the following : (any three) (a) What is peptide linkage ? (b) What type of bonds hold a DNA double helix together ? (c) Which one of the following is a polysaccharide ? Sucrose, Glucose, Starch, Fructose (d) Give one example each for water-soluble vitamins and fat-soluble vitamins.$
Q.283 marks $\mathrm{(C_6H_{12}O_2)}$

Expt. No.	$\mathrm{[NO]/mol\ L^{-1}}$	$\mathrm{[Br_2]/mol\ L^{-1}}$	Initial Rate $\mathrm{(mol\ L^{-1}\,s^{-1})}$
1	$0{\cdot}05$	$0{\cdot}05$	$1{\cdot}0 \times 10^{-3}$
2	$0{\cdot}05$	$0{\cdot}15$	$3{\cdot}0 \times 10^{-3}$
3	$0{\cdot}15$	$0{\cdot}05$	$9{\cdot}0 \times 10^{-3}$

Section D

Batteries and fuel cells are very useful forms of galvanic cell. Any battery or cell that we use as a source of electrical energy is basically a galvanic cell. However, for a battery to be of practical use it should be reasonably light, compact and its voltage should not vary appreciably during its use. There are mainly two types of batteries — primary batteries and secondary batteries. In the primary batteries, the reaction occurs only once and after use over a period of time the battery becomes dead and cannot be reused again, whereas the secondary batteries are rechargeable. Production of electricity by thermal plants is not a very efficient method and is a major source of pollution. To solve this problem, galvanic cells are designed in such a way that energy of combustion of fuels is directly converted into electrical energy, and these are known as fuel cells. One such fuel cell was used in the Apollo space programme.
Q.29 (a)1 mark $How do primary batteries differ from secondary batteries ?$
Q.29 (b)1 mark $1{\cdot}35$
Q.29 (c)2 marks $Write the reactions involved in the recharging of the lead storage battery.$
OR
Q.29 (c) OR2 marks $Write two advantages of fuel cells over other galvanic cells.$
The Valence Bond Theory (VBT) explains the formation, magnetic behaviour and geometrical shapes of coordination compounds whereas 'The Crystal Field Theory' for coordination compounds is based on the effect of different crystal fields (provided by ligands taken as point charges), on the degeneracy of d-orbital energies of the central metal atom/ion. The splitting of the d-orbitals provides different electronic arrangements in strong and weak crystal fields. The crystal field theory attributes the colour of the coordination compounds to d-d transition of the electron. Coordination compounds find extensive applications in metallurgical processes, analytical and medicinal chemistry.
Q.30 (a)1 mark $What is crystal field splitting energy ?$
Q.30 (b)1 mark $\mathrm{[Ti(H_2O)_6]^{3+}}$
Q.30 (c)2 marks $\mathrm{[Cr(NH_3)_6]^{3+}}$
OR
Q.30 (c) OR2 marks $\mathrm{[Fe(CN)_6]^{3-}}$

Section E

5 marks each

Q.31 (a)5 marks $\mathrm{CO_2}$
OR
Q.31 (b)5 marks $25\,^{\circ}\mathrm{C}$
Q.325 marks $\xrightarrow[\mathrm{(ii)\ NaNO_2\,/\,Cu,\ \Delta}]{\mathrm{(i)\ HBF_4}}$
Q.33 (a)5 marks $\mathrm{d^4}$
OR
Q.33 (b)5 marks $\mathrm{Cu_2Cl_2}$

Section A

1 mark each

Q.11 mark $The most stable oxidation state of Iron is :$
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Q.21 mark $\mathrm{CH_3MgBr}$
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Q.31 mark $Nucleotides are composed of a :$
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Q.41 mark $\mathrm{S_N1}$
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Q.51 mark $0{\cdot}54$
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Q.61 mark $\mathrm{A_2} + \mathrm{B_2} \longrightarrow 2\mathrm{AB}$
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Q.71 mark $Decarboxylation of sodium benzoate on heating with soda lime gives :$
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Q.81 mark $\mathrm{CH_3} - \overset{\mathrm{O}}{\overset{\|}{\mathrm{C}}} - \mathrm{CH_2} - \overset{\mathrm{O}}{\overset{\|}{\mathrm{C}}} - \mathrm{H}$
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Q.91 mark $Dehydration of tertiary alcohols with Cu at 573 K gives :$
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Q.101 mark $In the Arrhenius equation, when log k is plotted against 1/T, a straight line is obtained whose :$
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Q.111 mark $Phenol on reaction with aqueous bromine at room temperature gives :$
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Q.121 mark $The specific sequence in which amino acids are arranged in a protein is called :$
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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 $Assertion (A) : Aniline is a stronger base than ammonia. Reason (R) : The unshared electron pair on nitrogen atom in aniline becomes less available for protonation due to resonance.$
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Q.141 mark $\mathrm{pK_a}$
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Q.151 mark $Assertion (A) : Transition metals have high enthalpy of atomization. Reason (R) : This is because transition metals have low melting points.$
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Q.161 mark $Assertion (A) : When NaCl is added in water, elevation in boiling point is observed. Reason (R) : Elevation in boiling point is a colligative property.$
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Section B

2 marks each

Q.17 (a)2 marks $\mathrm{C_6H_5-CH=CH_2} + \mathrm{HBr} \longrightarrow$
OR
Q.17 (b)2 marks $Give reasons for the following : (i) Grignard reagent should be prepared under anhydrous conditions. (ii) Alkyl halides give alcohol with aqueous KOH whereas in the presence of alcoholic KOH, alkenes are formed.$
Q.182 marks $\mathrm{Br_2}$
Q.192 marks $\mathrm{H_2N - NH_2}$
Q.202 marks $\mathrm{Fe^{2+}}$
Q.212 marks $Write two differences between order of reaction and molecularity of reaction.$

Section C

3 marks each

Q.223 marks $\mathrm{(C_6H_{12}O_2)}$
Q.233 marks $Answer the following : (any three) (a) What is peptide linkage ? (b) What type of bonds hold a DNA double helix together ? (c) Which one of the following is a polysaccharide ? Sucrose, Glucose, Starch, Fructose (d) Give one example each for water-soluble vitamins and fat-soluble vitamins.$
Q.243 marks $\mathrm{CH_3CH_2OH} \xrightarrow[443\ \mathrm{K}]{\mathrm{H^+}} \mathrm{CH_2=CH_2}$
Q.253 marks $\mathrm{[Cr(NH_3)_5Cl]Cl_2}$
Q.263 marks $\mathrm{CH_3-CH=CH-Br}$

Q.273 marks

2\mathrm{NO\,(g)} + \mathrm{Br_2\,(g)} \rightarrow 2\mathrm{NOBr\,(g)}

Q.283 marks $0{\cdot}05$

Expt. No.	$\mathrm{[NO]/mol\ L^{-1}}$	$\mathrm{[Br_2]/mol\ L^{-1}}$	Initial Rate $\mathrm{(mol\ L^{-1}\,s^{-1})}$
1	$0{\cdot}05$	$0{\cdot}05$	$1{\cdot}0 \times 10^{-3}$
2	$0{\cdot}05$	$0{\cdot}15$	$3{\cdot}0 \times 10^{-3}$
3	$0{\cdot}15$	$0{\cdot}05$	$9{\cdot}0 \times 10^{-3}$

Section D

The Valence Bond Theory (VBT) explains the formation, magnetic behaviour and geometrical shapes of coordination compounds whereas 'The Crystal Field Theory' for coordination compounds is based on the effect of different crystal fields (provided by ligands taken as point charges), on the degeneracy of d-orbital energies of the central metal atom/ion. The splitting of the d-orbitals provides different electronic arrangements in strong and weak crystal fields. The crystal field theory attributes the colour of the coordination compounds to d-d transition of the electron. Coordination compounds find extensive applications in metallurgical processes, analytical and medicinal chemistry.
Q.29 (a)1 mark $What is crystal field splitting energy ?$
Q.29 (b)1 mark $\mathrm{[Ti(H_2O)_6]^{3+}}$
Q.29 (c)2 marks $\mathrm{[Cr(NH_3)_6]^{3+}}$
OR
Q.29 (c) OR2 marks $\mathrm{[Fe(CN)_6]^{3-}}$
Batteries and fuel cells are very useful forms of galvanic cell. Any battery or cell that we use as a source of electrical energy is basically a galvanic cell. However, for a battery to be of practical use it should be reasonably light, compact and its voltage should not vary appreciably during its use. There are mainly two types of batteries — primary batteries and secondary batteries. In the primary batteries, the reaction occurs only once and after use over a period of time the battery becomes dead and cannot be reused again, whereas the secondary batteries are rechargeable. Production of electricity by thermal plants is not a very efficient method and is a major source of pollution. To solve this problem, galvanic cells are designed in such a way that energy of combustion of fuels is directly converted into electrical energy, and these are known as fuel cells. One such fuel cell was used in the Apollo space programme.
Q.30 (a)1 mark $How do primary batteries differ from secondary batteries ?$
Q.30 (b)1 mark $1{\cdot}35$
Q.30 (c)2 marks $Write the reactions involved in the recharging of the lead storage battery.$
OR
Q.30 (c) OR2 marks $Write two advantages of fuel cells over other galvanic cells.$

Section E

5 marks each

Q.31 (a)5 marks $\mathrm{d^4}$
OR
Q.31 (b)5 marks $\mathrm{Cu_2Cl_2}$
Q.32 (a)5 marks $\mathrm{CO_2}$
OR
Q.32 (b)5 marks $25\,^{\circ}\mathrm{C}$
Q.335 marks $\xrightarrow[\mathrm{(ii)\ NaNO_2\,/\,Cu,\ \Delta}]{\mathrm{(i)\ HBF_4}}$

Section A

1 mark each

Q.11 mark $\mathrm{Cr_2O_7^{2-}} \rightleftharpoons 2\mathrm{CrO_4^{2-}}$
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Q.21 mark $Which of the following is the strongest acid ?$
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Q.31 mark $Maltose is made up of :$
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Q.41 mark $The system that forms maximum boiling azeotrope is :$
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Q.51 mark $A zero-order reaction is one whose rate is independent of :$
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Q.61 mark $In the Arrhenius equation, when log k is plotted against 1/T, a straight line is obtained whose :$
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Q.71 mark $Which of the following is most reactive towards nucleophilic substitution reaction ?$
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Q.81 mark $\mathrm{=O}$
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Q.91 mark $Which of the following has the highest boiling point ?$
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Q.101 mark $Phenol does not undergo nucleophilic substitution reaction easily due to :$
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Q.111 mark $\mathrm{CH_3-CH(CH_3)-CH_2-OH}$
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Q.121 mark $All proteins on hydrolysis give :$
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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 $Assertion (A) : Fluoroacetic acid is stronger acid than chloroacetic acid. Reason (R) : This is due to greater electron withdrawing nature of F than Cl.$
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Q.141 mark $p$
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Q.151 mark $\Delta_{\mathrm{mix}}\mathrm{H}$
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Q.161 mark $Assertion (A) : Separation of Zr and Hf is difficult. Reason (R) : Zr and Hf are radioactive.$
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Section B

2 marks each

Q.172 marks $\mathrm{H_2N-OH}$
Q.18 (a)2 marks $\mathrm{C_6H_5-CH=CH_2} + \mathrm{HBr} \longrightarrow$
OR
Q.18 (b)2 marks $Give reasons for the following : (i) Grignard reagent should be prepared under anhydrous conditions. (ii) Alkyl halides give alcohol with aqueous KOH whereas in the presence of alcoholic KOH, alkenes are formed.$
Q.192 marks $\rightarrow$
Q.202 marks $Write the chemical equations when : (a) Ethanal is treated with 2,4-dinitrophenylhydrazine ? (b) Propanone is treated with Zn(Hg) and conc. HCl ?$
Q.212 marks $\mathrm{Fe^{2+}}$

Section C

3 marks each

Q.223 marks

2\mathrm{NO\,(g)} + \mathrm{Br_2\,(g)} \rightarrow 2\mathrm{NOBr\,(g)}

Q.233 marks $0{\cdot}05$
Q.243 marks $\mathrm{CH_3-CH=CH-Br}$
Q.253 marks $\mathrm{[Cr(NH_3)_5Cl]Cl_2}$
Q.263 marks $\mathrm{(C_6H_{12}O_2)}$
Q.273 marks $\mathrm{CH_3CH_2OH} \xrightarrow[443\ \mathrm{K}]{\mathrm{H^+}} \mathrm{CH_2=CH_2}$
Q.283 marks $Answer the following : (any three) (a) What is peptide linkage ? (b) What type of bonds hold a DNA double helix together ? (c) Which one of the following is a polysaccharide ? Sucrose, Glucose, Starch, Fructose (d) Give one example each for water-soluble vitamins and fat-soluble vitamins.$

Expt. No.	$\mathrm{[NO]/mol\ L^{-1}}$	$\mathrm{[Br_2]/mol\ L^{-1}}$	Initial Rate $\mathrm{(mol\ L^{-1}\,s^{-1})}$
1	$0{\cdot}05$	$0{\cdot}05$	$1{\cdot}0 \times 10^{-3}$
2	$0{\cdot}05$	$0{\cdot}15$	$3{\cdot}0 \times 10^{-3}$
3	$0{\cdot}15$	$0{\cdot}05$	$9{\cdot}0 \times 10^{-3}$

Section D

Batteries and fuel cells are very useful forms of galvanic cell. Any battery or cell that we use as a source of electrical energy is basically a galvanic cell. However, for a battery to be of practical use it should be reasonably light, compact and its voltage should not vary appreciably during its use. There are mainly two types of batteries — primary batteries and secondary batteries. In the primary batteries, the reaction occurs only once and after use over a period of time the battery becomes dead and cannot be reused again, whereas the secondary batteries are rechargeable. Production of electricity by thermal plants is not a very efficient method and is a major source of pollution. To solve this problem, galvanic cells are designed in such a way that energy of combustion of fuels is directly converted into electrical energy, and these are known as fuel cells. One such fuel cell was used in the Apollo space programme.
Q.29 (a)1 mark $How do primary batteries differ from secondary batteries ?$
Q.29 (b)1 mark $1{\cdot}35$
Q.29 (c)2 marks $Write the reactions involved in the recharging of the lead storage battery.$
OR
Q.29 (c) OR2 marks $Write two advantages of fuel cells over other galvanic cells.$
The Valence Bond Theory (VBT) explains the formation, magnetic behaviour and geometrical shapes of coordination compounds whereas 'The Crystal Field Theory' for coordination compounds is based on the effect of different crystal fields (provided by ligands taken as point charges), on the degeneracy of d-orbital energies of the central metal atom/ion. The splitting of the d-orbitals provides different electronic arrangements in strong and weak crystal fields. The crystal field theory attributes the colour of the coordination compounds to d-d transition of the electron. Coordination compounds find extensive applications in metallurgical processes, analytical and medicinal chemistry.
Q.30 (a)1 mark $What is crystal field splitting energy ?$
Q.30 (b)1 mark $\mathrm{[Ti(H_2O)_6]^{3+}}$
Q.30 (c)2 marks $\mathrm{[Cr(NH_3)_6]^{3+}}$
OR
Q.30 (c) OR2 marks $\mathrm{[Fe(CN)_6]^{3-}}$

Section E

5 marks each

Q.315 marks $\xrightarrow[\mathrm{(ii)\ NaNO_2\,/\,Cu,\ \Delta}]{\mathrm{(i)\ HBF_4}}$
Q.32 (a)5 marks $\mathrm{d^4}$
OR
Q.32 (b)5 marks $\mathrm{Cu_2Cl_2}$
Q.33 (a)5 marks $\mathrm{CO_2}$
OR
Q.33 (b)5 marks $25\,^{\circ}\mathrm{C}$