JEE Main 2025 Apr 3 Shift 2, Chemistry Q20: Factors Affecting The Rate of a Chemical Reaction

JEE Main2025Apr 3, Shift 2Chemistry

Consider the following statements related to temperature dependence of rate constants. Identify the correct statements,

A. The Arrhenius equation holds true only for an elementary homogenous reaction.

B. The unit of A is same as that of k in Arrhenius equation.

C. At a given temperature, a low activation energy means a fast reaction.

D. A and Ea as used in Arrhenius equation depend on temperature.

E. When Ea $>>$ RT. A and Ea become interdependent.

Choose the correct answer from the options given below :

Solution

Evaluate each claim against the Arrhenius relation $k = A e^{- E_{a} / R T}$ .

(A) False. Arrhenius behaviour applies broadly, including many complex reactions, not only elementary homogeneous ones.

(B) True. Since $e^{- E_{a} / R T}$ is dimensionless, $A$ must carry the same units as $k$ .

(C) True. For two reactions at the same temperature, the one with smaller $E_{a}$ has a larger Boltzmann factor and thus a larger rate constant.

(D) False. To a good approximation, $A$ and $E_{a}$ are treated as temperature-independent constants of the reaction.

(E) False. There is no general result that $A$ and $E_{a}$ become interdependent when $E_{a} ≫ R T$ .

$∴$ Only B and C are correct.

Concept behind this question

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