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QUESTION PAPER

2023 BOARD EXAM

CBSE CLASS 12-PCM CHEMISTRY Board Paper 2023 — Set 2

2023

CHEMISTRY

CLASS 12-PCM

CBSE EXAMINATION PAPER-2023 CHEMISTRY

CBSE EXAMINATION PAPER-2023

CHEMISTRY

(Solved)

Time allowed : 3 hours

Maximum Marks : 17

General Instructions :

Read the following instructions carefully and follow them :

This question paper contains 17 questions. All questions are compulsory.
This question paper is divided into 3 sections.
Section A – questions number 1 to 1 are case based questions
Section B – questions number 2 to 15 are multiple choice questions
Section C – questions number 16 to 17 are very short answer
There is no overall choice given in the question paper. However, an internal choice has been provided in few questions.
Use of calculator is NOT allowed.

Section A

Question 1. The carbon – oxygen double bond is polarised in aldehydes and ketones due to higher electronegativity of oxygen relative to carbon. Therefore they undergo nucleophilic addition reactions with a number of nucleophiles such as HCN, NaHSO3, alcohols, ammonia derivatives and Grignard reagents. Aldehydes are easily oxidised by mild oxidising agents as compared to ketones. The carbonyl group of carboxylic acid does not give reactions of aldehydes and ketones. Carboxylic acids are considerably more acidic than alcohols and most of simple phenols.

Section B

Question 2.

The conversion of an alkyl halide into an alkene by alcoholic KOH is classified as

[1 Marks]

(A) a dehydrohalogenation reaction
(B) an addition reaction
(C) a dehydration reaction
(D) a substitution reaction

Question 3.

The oxidation state of Fe in [Fe(CO)₅] is

[1 Marks]

(A) +5
(B) +3
(C) +2
(D) 0

Question 4.

The slope in the plot of ln[R] vs. time for a first order reaction is

[1 Marks]

(A) + k
(B) – k
(C) + k/2.303
(D) – k/2.303

Question 5.

An α-helix is a structural feature of

[1 Marks]

(A) Nucleotides
(B) Starch
(C) Polypeptides
(D) Sucrose

Question 6.

Racemisation occurs in

[1 Marks]

(A) Sₙ1 reaction
(B) Sₙ2 reaction
(C) Sₙ2 reaction as well as Sₙ1 reaction
(D) Neither Sₙ1 nor Sₙ2 reaction

Question 7.

Value of Henry’s constant Kₕ:

[1 Marks]

(A) decreases with increase in temperature.
(B) remains constant.
(C) increases with increase in temperature.
(D) increases with decrease in temperature.

Question 8.

Which of the following solutions of KCl will have the highest value of molar conductivity?

[1 Marks]

(A) 1 M
(B) 0.1 M
(C) 0.5 M
(D) 0.01 M

Question 9.

Which of the following reactions are feasible?

[1 Marks]

(A) Both (a) and (b)
(B) CH₃CH₂Br + Na⁺ O–C(CH₃)₃ → CH₃CH₂–O–C(CH₃)₃
(C) Neither (a) nor (b)
(D) (CH₃)₃C–Cl + Na⁺ O–CH₂CH₃ → CH₃CH₂–O–C(CH₃)₃

Question 10.

Which of the following is most reactive in nucleophilic addition reactions?

[1 Marks]

(A) CH₃COC₂H₅
(B) CH₃CHO
(C) CH₃COCH₃
(D) HCHO

Question 11.

For the reaction 3A → 2B, rate of reaction + d[B]/dt is equal to

[1 Marks]

(A) +(2d[A]/dt)
(B) –(3/2)d[A]/dt
(C) –(2/3)d[A]/dt
(D) –(1/3)d[A]/dt

Question 12.

Which of the following characteristics of transition metals is associated with their catalytic activity?

[1 Marks]

(A) High enthalpy of atomisation
(B) Variable oxidation states
(C) Paramagnetic nature
(D) Colour of hydrated ions

Question 13.

The formula of the complex dichloridobis(ethane–1, 2-diamine) platinum(IV) nitrate is

[1 Marks]

(A) [Pt(en)₂(NO₃)₂]Cl₂
(B) [Pt Cl₂(en)₂ (NO₃)]NO₃
(C) [Pt Cl₂(en)₂](NO₃)₂
(D) [Pt Cl₂(en)₂ (NO₃)₂]

Question 14.

Assertion (A) : Osmotic pressure is a colligative property.

Reason (R) : Osmotic pressure is proportional to the molality.

(A) (A) is false, but (R) is true.
(B) Both (A) and (R) are true and (R) is the correct explanation of (A).
(C) (A) is true, but (R) is false
(D) Both (A) and (R) are true, but (R) is not the correct explanation of (A).

Question 15.

Assertion (A) : Copper is a non-transition element.

Reason (R) : Copper has completely filled d-orbitals in its ground state.

[1 Marks]

(A) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(B) (A) is false, but (R) is true.
(C) (A) is true, but (R) is false.
(D) Both (A) and (R) are true and (R) is the correct explanation of (A).

Section C

Question 16.

The vapour pressure of pure liquid X and pure liquid Y at 25 °C are 120 mm Hg and 160 mm Hg respectively. If equal moles of X and Y are mixed to form an ideal solution, calculate the vapour pressure of the solution.

[2 Marks]

Question 17.

Define fuel cell with an example. What advantages do the fuel cells have over primary and secondary batteries ?

[2 Marks]

Paper Details

CBSE Board Exam 2023

Class

CLASS 12-PCM

Subject

CHEMISTRY

Year

2023

Set

Set 2

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