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Which of the following statements are correct for a first-order reaction A → Products? (A) The degree of dissociation equals (1 - e^(-kt)). (B) A graph of 1/[A] versus time is a straight line. (C) The time required to complete 75% of the reaction is twice the half-life (t_(1/2)). (D) The pre-exponential factor A in the Arrhenius equation carries dimensions of time^(-1).
- (A)
- (B)
- (C)
- (D)
Correct answer: (D)
Solution
Statement A: correct formula. Statement B: 1/[A] vs t is linear for SECOND order, not first. Statement C: t_(1/2) = ln2/k; t_(75%) = ln4/k = 2 * ln2/k = 2 * t_(1/2), so C is correct. Statement D: In Arrhenius equation k = A * e^(-Ea/RT), A has same dimensions as k, which is time^(-1) for first order. So A, C, D are correct. The answer matching only one listed option (D) is tricky — in JEE Adv multi-correct format, the intended answer is (A), (C), (D).
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