Chemistry · 2022

CBSE Class 12 Chemistry 2022 — Previous-Year Question Paper

CBSE Class XII Board 2022 · Set 56/1/1

Real board examination

Sets

About the 2022 exam: 2022 was CBSE's special COVID year: the board exam was split into two terms instead of one 70-mark paper. Term 1 (Dec 2021) was multiple-choice only; Term 2 (2022 — the papers shown here) was a shorter subjective paper of just 12 questions for 35 marks. So the smaller size IS the real exam that year, not missing content. The three distinct series here are complete (12/12), taken verbatim from the official CBSE papers. Some topics examined then have since been removed from the syllabus — badged and filterable above.

This paper has 1 question on a topic removed in CBSE’s 2023-24 syllabus update (each marked Not in syllabus). It’s kept for historical accuracy — the exam really asked it that year — but isn’t in the current syllabus and doesn’t count toward a concept’s importance. Switch to to focus on what’s still examinable.

About this paper

The real Class-12 board examination held in 2022. Every question below is solved the concept-first way. Sample papers are labelled honestly — never shown as a past exam.

Total marks: 35
Questions: 12
Duration: 120 min
Sections: 3

The marks / questions / duration above are the official exam pattern. We currently have 12 of this paper’s questions (100% of the full paper), with 12 fully solved. Questions we couldn’t yet extract or verify are held — never shown as complete.

Sections & marks

Section	Type	Questions	Marks each	Total
ASection A	Very short answer	3	2	6
BSection B	Short answer	8	3	24
CSection C	Case-based	1	5	5
Total		12		35

The question paper

The questions we hold for this paper, laid out by section. Solutions are on the Answers tab.

Board Examination

Chemistry

CBSE Class XII Board 2022 · Set 56/1/1

Series/Set: 56/1/1Roll No. ________

Time Allowed: 2 hoursMaximum Marks: 35

General Instructions

This question paper contains 12 questions divided into 3 sections — A, B, C.
Section A comprises 3 questions of 2 marks each (Very short answer).
Section B comprises 8 questions of 3 marks each (Short answer).
Section C comprises 1 question of 5 marks each (Case-based).

Above is the official exam pattern. The questions printed below are those we currently hold for this paper.

Section A

Very short answer · 2 marks each · 3 of 3 shown

Q1.

Define rate of reaction. Write two factors that affect the rate of reaction.

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Q2.

Arrange the following compounds as directed : (any Two)

(i) In decreasing order of basic strength in aqueous solution : $C_2H_5NH_2$ , $(C_2H_5)_2NH$ , $(C_2H_5)_3N$
(ii) In increasing order of solubility in water : $(C_2H_5)_2NH$ , $C_2H_5NH_2$ , $C_6H_5NH_2$
(iii) In decreasing order of their pKb values : $C_6H_5NH_2$ , $C_2H_5NH_2$ , $NH_3$

[2]

Q3.

Write the Nernst equation for the following cell reaction :

Zn(s) + Cu^{2+}(aq) \rightarrow Zn^{2+}(aq) + Cu(s)

How will the

E_{cell}

be affected when concentration of

(i) $Cu^{2+}$ ions is increased and
(ii) $Zn^{2+}$ ions is increased ?

[2]

Section B

Short answer · 3 marks each · 8 of 8 shown

Q1.

Following ions of 3d-transition series are given :

Ti^{4+}

V^{3+}

Cr^{3+}

Mn^{3+}

(Atomic number : Ti = 22, V = 23, Cr = 24, Mn = 25) Identify the ion which is

(i) most stable in aqueous solution.
(ii) a strong oxidising agent.
(iii) colourless in aqueous solution. Give suitable reason in each.

[3]

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Q2.

(a) (i) On the basis of crystal field theory, write the electronic configuration for d⁴ ion if Δ₀ < P. (ii) Using valence bond theory, predict the hybridization and magnetic character of [Ni(CN)₄]²⁻. (Atomic number of Ni = 28) (iii) Write the formula of the following complex using IUPAC norms : Dichloridobis(ethane-1,2-diamine)cobalt(III) OR (b) When a co-ordination compound NiCl₂ · 6H₂O mixed with AgNO₃, 2 moles of AgCl are precipitated per mole of the compound. Write (i) Structural formula of the complex. (ii) Secondary valency of 'Ni' in the complex. (iii) IUPAC name of the complex.

[3]

Q3.

A first order reaction is 50% complete in 40 minutes. Calculate the time required for the completion of 90% of reaction. [Given : log 2 = 0.3010, log 10 = 1]

[3]

Q4.

(a) Illustrate the following reactions giving suitable example in each case : (i) Gabriel phthalimide synthesis. (ii) Carbylamine reaction. (iii) Hoffmann bromamide degradation reaction. OR (b) Write the structures of A, B and C in the following reactions : (i) CH₃CH₂Cl xrightarrowKCN A xrightarrowLiAlH₄ B xrightarrow[0°C]HNO₂ C (ii) CH₃COOH xrightarrowNH₃,Δ A xrightarrow[(b)H₂O](a)LiAlH₄ B xrightarrowC₆H₅SO₂Cl C

[3]

Q5.

(a) Account for the following : (i) Transition elements have higher enthalpies of atomisation. (ii) Separation of a mixture of Lanthanoid elements is difficult. (iii) The E°M²⁺/M value for copper is positive. OR (b) Define transition elements. Which of the d-block elements may not be regarded as the transition elements ? Why transition metals generally form coloured compounds ?

[3]

Q6.

An organic compound 'X' with the molecular formula C₅H₁₀O forms 2,4-DNP derivative, does not reduce Tollens' reagent but gives positive iodoform test on heating with I₂ in the presence of NaOH. Compound 'X' gives ethanoic acid and propanoic acid on vigorous oxidation. Write the (i) Structure of the compound 'X'. (ii) Structure of the product obtained when compound 'X' reacts with 2,4-DNP reagent. (iii) Structures of the products obtained when compound 'X' is heated with I₂ in the presence of NaOH.

[3]

Q7.

(a) Write any three differences between physisorption and chemisorption. OR (b) Define the following terms with a suitable example in each : (i) Lyophilic sol (ii) Macromolecular colloid (iii) Coagulation

⚠ This question is not in the current syllabus — Surface Chemistry (removed 2023-24)

[3]

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Q8.

(a) The standard Gibbs energy (Δr G°) for the following cell reaction is -300 kJ mol⁻¹ : Zn(s) + 2Ag^+(aq) arrow Zn²⁺(aq) + 2Ag(s) Calculate E°cell for the reaction. (Given : 1F = 96500 mol⁻¹) (b) Calculate λ°m for MgCl₂ if λ° values for Mg²⁺ ion and Cl^- ion are 106 S cm² mol⁻¹ and 76.3 S cm² mol⁻¹ respectively.

[3]

Section C

Case-based · 5 marks each · 1 of 1 shown

Q1.

Read the passage given below and answer the questions that follow : Aldehydes, ketones and carboxylic acids are some of the important classes of organic compounds containing carbonyl group. These are highly polar molecules due to higher electro-negativity of oxygen relative to carbon in the carbonyl group. Aldehydes are prepared by dehydrogenation or controlled oxidation of primary alcohols and controlled reduction of acyl halides. Ketones are prepared by oxidation of secondary alcohols and hydration of alkynes. Aldehydes and ketones undergo nucleophilic addition reactions onto the carbonyl group but carboxylic acid does not undergo nucleophilic addition reaction. The alpha (α) hydrogens of aldehydes and ketones are acidic. Therefore aldehydes and ketones having at least one α-hydrogen undergo Aldol condensation. Aldehydes are easily oxidised by mild oxidising agents such as Tollens' reagent and Fehling's reagent. Carboxylic acids are prepared by the oxidation of primary alcohols, aldehydes and by hydrolysis of nitriles. Aromatic carboxylic acids are prepared by side-chain oxidation of alkyl benzenes. Carboxylic acids are considerably more acidic than alcohols and most of simple phenols. (a) Arrange the following in the increasing order of their reactivity towards nucleophilic addition reaction. : CH₃COCH₃, CH₃CHO, HCHO, C₆H₅COCH₃ (b) Give a simple chemical test to distinguish between Ethanal and Propanone. (c) Why carboxylic acid does not give nucleophilic addition reactions like aldehydes and ketones ? (d) (i) Why α-hydrogen of aldehydes and ketones are acidic in nature ? (ii) Write the products in the following : 2C₆H₅CHO xrightarrowConc.NaOH OR Write the major products of the following reactions : (i) C₆H₅CH₂CH₃ xrightarrow[(b)H^+](a)KMnO₄,KOH (ii) C₆H₅COCl xrightarrowH₂,Pd-BaSO₄

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