Reaction: A + B → C + D, follows the rate law: r = (2.31 × 10^-3 s^-1)[A]^1/2[B]^1/2. The reaction is started with 1.0 mole each of 'A' and 'B'. In what time, the moles of 'A' become 0.25?

Question

Prashant Kotian · Accepted Answer

Correct answer: D. Since A0 = B0 and the stoichiometry is 1:1, [A] = [B] at all times. The rate law simplifies to r = k[A]^1/2[A]^1/2 = k[A], making it a first-order reaction with k = 2.31 × 10^-3 s^-1. Moles drop from 1.0 to 0.25 (2 half-lives). t_1/2 = 0.693 / (2.31 × 10^-3) = 300 s. Time = 2 × 300 = 600 s. Therefore, correct answer is D.

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