Chemistry Reaction Kinetics ETEA 2022
PMDC Verified Question 33 of 80
One mole of a reactant reacts with a rate of \( 0.6 \text{ mol dm}^{-3} \text{s}^{-1} \). What is the rate constant of this reaction if reaction is first order?
A
\( 1 \text{ s}^{-1} \)
B
\( 0.3 \text{ s}^{-1} \)
C
\( 0.6 \text{ s}^{-1} \)
D
\( 0.9 \text{ s}^{-1} \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: \( 0.6 \text{ s}^{-1} \)
Concept:

The rate constant for a first-order reaction is found by dividing the given rate by the given concentration.

Formula:

$$ \text{Rate} = k[\text{A}]^{1} $$

Solution:

  • We are given Rate = \( 0.6 \text{ mol dm}^{-3} \text{s}^{-1} \).
  • We are given the concentration of the reactant is 1 mole (implied 1 \( \text{mol dm}^{-3} \) in a standard 1 \( \text{dm}^{3} \) vessel).
  • Substitute the values: \( 0.6 = k(1) \).
  • Therefore, \( k = 0.6 \text{ s}^{-1} \).


Why other options are incorrect:

Because the concentration is exactly 1, the numerical value of the rate constant exactly matches the numerical value of the rate. Dividing or multiplying by other factors is mathematically unjustified here.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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