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AIIMS2019Chemistry-Chemical Kinetics

AIIMS 2019 Chemistry Rate of Reaction MCQ Question

Type: MCQ-numerical-Medium-Class 12

For the reaction : A+2B→C+D\text{A} + 2\text{B} \rightarrow \text{C} + \text{D}, the expression of rate of reaction will

A

−11d[A]dt=−12d[B]dt\frac{-1}{1}\frac{\text{d[A]}}{\text{dt}} = \frac{-1}{2}\frac{\text{d[B]}}{\text{dt}}

B

11d[A]dt=−12d[B]dt\frac{1}{1}\frac{\text{d[A]}}{\text{dt}} = \frac{-1}{2}\frac{\text{d[B]}}{\text{dt}}

C

−11d[A]dt=12d[B]dt\frac{-1}{1}\frac{\text{d[A]}}{\text{dt}} = \frac{1}{2}\frac{\text{d[B]}}{\text{dt}}

D

11d[A]dt=−12d[B]dt\frac{1}{1}\frac{\text{d[A]}}{\text{dt}} = \frac{-1}{2}\frac{\text{d[B]}}{\text{dt}}

Correct Answer

Option A

Detailed Explanation

In the reaction A + 2B → C + D, the stoichiometric coefficients indicate that for every 1 mole of A consumed, 2 moles of B are consumed, and 1 mole each of C and D are produced. The rate of reaction can be expressed as -1/1 d[A]/dt = -1/2 d[B]/dt = +d[C]/dt = +d[D]/dt, which simplifies to a rate constant of 1, corresponding to option (A).

Options (B), (C), and (D) suggest different rate constants, which do not accurately reflect the stoichiometric relationships in the reaction; for instance, a rate of 2 or higher would imply an incorrect consumption or production ratio of the reactants and products. Understanding these relationships is crucial for accurately determining reaction rates in chemical kinetics.

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