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Assertion (A) : For a zero… (Class 12 Chemistry 2023, Q16)

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ChemistryCBSE Class 12 · Board exam 2023, set 56/5/1 · 1 mark · Assertion-reason

CBSE Class 12 Chemistry 2023: question 16

Set in the CBSE Class 12 board exam of 2023, paper 56/5/1, section A, question 16, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q16 · 1 mark · Assertion-reasonCompetency-basedChemical Kinetics

Assertion (A) : For a zero order reaction the unit of rate constant and rate of reaction are same.
Reason (R) : Rate of reaction for zero order reaction is independent of concentration of reactant.

  1. (A)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
  2. (B)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
  3. (C)Assertion (A) is true, but Reason (R) is false.
  4. (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 56/5/1.

Hints

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

Hint 1

Write the rate law for a zero order reaction.

Hint 2

Compare the units of k and of rate.

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.

  1. For a zero order reaction, rate , so the rate is independent of concentration. Hence k has the same unit as rate, mol L⁻¹ s⁻¹.

    1 mark

  2. Both statements are true and R explains A. Option (B) is also accepted by the scheme.

Answer: (A) (scheme also accepts B)

Where the marks are

  • Recognises that both statements are true (1 mark)

Revise the chapter

  • Chapter: Chemical Kinetics (notes, formulas, where marks are lost and every past question)
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 56/5/1: 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.