Chemistry Reaction Kinetics PMDC 2020
PMDC Verified Question 49 of 80
For which of the following order of the reaction, rate of reaction is inversely proportional to the concentration reaction?
A
1st order reaction
B
2nd order reaction
C
Negative order of reaction
D
Zero order of reaction
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Negative order of reaction
Concept:

An inverse relationship in a rate law implies that as the concentration of a reactant increases, the rate of the overall reaction actually decreases.

Formula:

$$ \text{Rate} \propto [\text{A}]^{-n} \implies \text{Rate} \propto \frac{1}{[\text{A}]^n} $$

Solution:

  • Mathematically, a variable in the denominator corresponds to a negative exponent.
  • If the rate is inversely proportional to concentration, the exponent in the rate law must be negative.
  • This is referred to as a negative order of reaction (often seen when a product or reactant acts as an inhibitor).


Why other options are incorrect:

Positive orders (1st, 2nd) mean rate increases with concentration. Zero order means rate is constant regardless of concentration.

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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