For a first-order reaction: A → Product, the initial concentration of A is 0.1 M and after time 40 min, it becomes 0.025 M. What is the rate of reaction at reactant concentration 0.01 M?

Question

Prashant Kotian · Accepted Answer

Correct answer: A. [A] drops from 0.1 M to 0.025 M (1/4th of initial), meaning 2 half-lives have passed in 40 min. So, t1/2 = 20 min. k = 0.693 / 20 = 0.03465 min^-1. Rate = k[A] = 0.03465 × 0.01 = 3.465 × 10^-4 M min^-1. Therefore, correct answer is A.

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