Assertion (A) : The molecularity of the reaction H_2 + Br_2 → 2HBr appears to be 2. Reason (R) : Two molecules of the reactants are involved in the given elementary reaction. (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A). (B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A). (C) Assertion (A) is true, but Reason (R) is false. (D) Assertion (A) is false, but Reason (R) is true.

ChemistryCBSE Class 12 · Board exam 2023, set 56/1/1 · 1 mark · Assertion-reason

CBSE Class 12 Chemistry 2023: question 17

Set in the CBSE Class 12 board exam of 2023, paper 56/1/1, section A, question 17, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q17 · 1 mark · Assertion-reasonCompetency-basedChemical Kinetics

Assertion (A) : The molecularity of the reaction $H_{2} + B r_{2} \to 2HBr$ appears to be 2.
Reason (R) : Two molecules of the reactants are involved in the given elementary reaction.

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

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 56/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Define molecularity.

Hint 2

Count the reactant molecules in the equation.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

Molecularity is the number of reacting species colliding in an elementary step.
Taken as an elementary step, one $H_{2}$ and one $B r_{2}$ molecule collide, so the molecularity appears to be 2. R correctly explains A. Option (A).
1 mark

Answer: Option (A)

Where the marks are

Both true, R explains A (1 mark)

Revise the chapter

Chapter: Chemical Kinetics (notes, formulas, where marks are lost and every past question)
Topic: Rate Law, Order and Molecularity

Practise this chapterBoard-style questions from Chemical Kinetics, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 56/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.

CBSE Class 12 Chemistry 2023: question 17

Hints

Step-by-step solution

Revise the chapter

More questions from Chemical Kinetics