Chemistry · 2022 · Set 56/4/1

CBSE Class 12 Chemistry 2022 — Set 56/4/1

CBSE Class XII Board 2022 · Set 56/4/1

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 56/4/1

Series/Set: 56/4/1Roll 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.

Arrange the following compounds in the increasing order of their property indicated : (Any two)

(i) Acetaldehyde, Benzaldehyde, Acetophenone, Acetone (Reactivity towards HCN)
(ii) $(CH_3)_2CHCOOH$ , $CH_3CH_2CH(Br)COOH$ , $CH_3CH(Br)CH_2COOH$ (Acidic strength)
(iii) $CH_3CH_2OH$ , $CH_3CHO$ , $CH_3COOH$ (Boiling point)

[2]

Q2.

In a plot of

\Lambda_m

against the square root of concentration (

C^{1/2}

) for strong and weak electrolyte, the value of limiting molar conductivity of a weak electrolyte cannot be obtained graphically. Suggest a way to obtain this value. Also state the related law, if any.

[2]

Q3.

Write reasons for the following statements :

(i) Benzoic acid does not undergo Friedel-Crafts reaction.
(ii) Oxidation of aldehydes is easier than that of ketones.

[2]

Section B

Short answer · 3 marks each · 8 of 8 shown

Q1.

(a) Write reasons for the following :

(i) Ethylamine is soluble in water whereas aniline is insoluble.
(ii) Amino group is o- and p-directing in aromatic electrophilic substitution reactions, but aniline on nitration gives a substantial amount of m-nitroaniline.
(iii) Amines behave as nucleophiles.

(OR)

(b) How will you carry out the following conversions :

(i) Nitrobenzene to Aniline
(ii) Ethanamide to Methanamine
(iii) Ethanenitrile to Ethanamine

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Q2.

(a) (i) Write the electronic configuration of d⁵ on the basis of crystal field splitting theory if Δo < P. (ii) [Fe(CN)₆]³⁻ is weakly paramagnetic whereas [Fe(CN)₆]⁴⁻ is diamagnetic. Give reason to support this statement. [Atomic no. : Fe = 26] (iii) Write the number of ions produced from the complex [Co(NH₃)₆]Cl₂ in solution. OR (b) (i) Calculate the spin only magnetic moment of the complex [CoF₆]³⁻. (Atomic no. of Co = 27) (ii) Write the IUPAC name of the given complex : [CrCl₂(H₂O)₄]Cl (iii) Which out of the two complexes is more stable and why ? [Fe(H₂O)₆]³⁺, [Fe(C₂O₄)₃]³⁻

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Q3.

(i) Which ion amongst the following is colourless and why ? Ti⁴⁺, Cr³⁺, V³⁺ (Atomic number of Ti = 22, Cr = 24, V = 23) (ii) Why is Mn²⁺ much more resistant than Fe²⁺ towards oxidation ? (iii) Highest oxidation state of a metal is shown in its oxide or fluoride only. Justify the statement.

[3]

Q4.

A compound 'A' (C₂H₄O) on oxidation gives 'B' (C₂H₄O₂). 'A' undergoes Iodoform reaction to give yellow precipitate and reacts with HCN to form the compound 'C'. 'C' on hydrolysis gives 2-hydroxypropanoic acid. Identify the compounds 'A', 'B' and 'C'. Write down equations for the reactions involved.

[3]

Q5.

Observe the given figure and answer the following questions : The figure is a straight-line plot of log (x)/(m) (y-axis) against log p (x-axis) with a positive slope and a positive intercept on the log (x)/(m) axis (the Freundlich adsorption isotherm, where (x)/(m) is the mass of gas adsorbed per gram of adsorbent and p is the pressure). (i) Write the expression for adsorption of gases on solids in the form of an equation. (ii) What is the slope of the graph ? (iii) What does the intercept of the line represent ?

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

[3]

Q6.

(a) Write equations involved in the following reactions : (i) Ethanamine reacts with acetyl chloride. (ii) Aniline reacts with bromine water at room temperature. (iii) Aniline reacts with chloroform and ethanolic potassium hydroxide. OR (b) (i) Write the IUPAC name for the following organic compound : (CH₃CH₂)₂NCH₃ (ii) Write the equations for the following : (I) Gabriel phthalimide synthesis (II) Hoffmann bromamide degradation

[3]

Q7.

Write the Nernst equation and calculate emf of the following cell at 298 K : Cr|Cr³⁺(0.1M)||Fe²⁺(0.01M)|Fe Given : E^°Cr³⁺/Cr = -0.75 V, E^°Fe²⁺/Fe = -0.45 V (log 10 = 1)

[3]

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Q8.

(a) (i) Silver atom has completely filled d-orbitals in its ground state, it is still considered to be a transition element. Justify the statement. (ii) Why are E^°M²⁺/M values of Mn and Zn more negative than expected ? (iii) Why do transition metals form alloys ? OR (b) Answer the following questions on the basis of the figure given below : The figure is a plot of enthalpy of atomisation (ΔaH^° / kJ mol⁻¹, y-axis) against atomic number (x-axis) showing three curves labelled Series 1, Series 2 and Series 3 (the 3d, 4d and 5d transition series); each curve rises to a maximum near the middle of its series and falls towards the ends, with Series 3 generally the highest and Series 1 the lowest. (i) Which element in 3d series has lowest enthalpy of atomisation ? (ii) Why do metals of the second and third series have greater enthalpies of atomisation ? (iii) Why are enthalpies of atomisation of transition metals quite high ?

[3]

Section C

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

Q1.

Read the passage given below and answer the questions that follow : The rate law for a chemical reaction relates the reaction rate with the concentrations or partial pressures of the reactants. For a general reaction aA + bB arrow C with no intermediate steps in its reaction mechanism, meaning that it is an elementary reaction, the rate law is given by r = k[A]x[B]y, where [A] and [B] express the concentrations of A and B in moles per litre. Exponents x and y vary for each reaction and are determined experimentally. The value of k varies with conditions that affect reaction rate, such as temperature, pressure, surface area, etc. The sum of these exponents is known as overall reaction order. A zero order reaction has a constant rate that is independent of the concentration of the reactants. A first order reaction depends on the concentration of only one reactant. A reaction is said to be second order when the overall order is two. Once we have determined the order of the reaction, we can go back and plug in one set of our initial values and solve for k. (i) Calculate the overall order of a reaction which has the following rate expression : Rate = k[A]1/2[B]3/2 (ii) What is the effect of temperature on rate of reaction ? (iii) What is meant by rate of a reaction ? (iv) (a) A first order reaction takes 77.78 minutes for 50% completion. Calculate the time required for 30% completion of this reaction. (log 10 = 1, log 7 = 0.8450) OR (b) A first order reaction has a rate constant 1 × 10⁻³ per sec. How long will 5 g of this reactant take to reduce to 3 g ? (log 3 = 0.4771; log 5 = 0.6990)

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