For a first order reaction, A → P, t1/2 (half-life) is 10 days. The time required for 1/4th conversion of A(in days) is – [ln2 = 0.693, ln3 = 1.1] [JEE-Main On line-2018]

Correct answer: 4.1

Solution

For first order, k = ln2/t_half = 0.693/10. For 1/4 (25%) conversion, 75% remains: t = (1/k) ln(1/0.75) = (1/k) ln(4/3) = (10/0.693)(2x0.693 - 1.1) ~ 4.1 days.

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