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Assertion (A) : The units… (Class 12 Chemistry 2024, Q14)

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ChemistryCBSE Class 12 · Board exam 2024, set 56/5/1 · 1 mark · Assertion-reason

CBSE Class 12 Chemistry 2024: question 14

Set in the CBSE Class 12 board exam of 2024, paper 56/5/1, section A, question 14, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q14 · 1 mark · Assertion-reasonCompetency-basedChemical Kinetics

Assertion (A) : The units of rate constant of a zero order reaction and rate of reaction are the same.
Reason (R) : In zero order reaction, the rate of reaction is independent of the concentration of reactants.

  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 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 2024 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 n = 0.

Hint 2

Compare the units of k and of the 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 both have units of mol L s. Assertion is true.

  2. Because the rate does not depend on concentration, rate equals , which is why their units are the same. Reason is true and explains the assertion. Option (A).

    1 mark

Answer: Option (A) (scheme also accepts B)

Where the marks are

  • Both statements true; option A or B accepted (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 paper2024 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.