A flask contains a mixture of compounds A and B. Both compounds decompose by first-order kinetics. The half-lives for A and B are 300 s and 180 s, respectively. If the concentrations of A and B are eq

Question

A flask contains a mixture of compounds A and B. Both compounds decompose by first-order kinetics. The half-lives for A and B are 300 s and 180 s, respectively. If the concentrations of A and B are equal initially, the time required for the concentration of A to be four times that of B (in s) is : (use ln 2 = 0.693)

(A) 120
(B) 300
(C) 180
(D) 900

Prashant Kotian · Accepted Answer

Correct answer: D. Ct = C0 e–kt 2 ln kA         / T ln k (Ct),A = (C0)A t kA e 2 ln kB  (Ct),B = (C0)B t kB e t) k k ( A B A t B t B A e ), C ( ), C ( ), C ( ), C (    4 = t) k k ( B A e  2 ln2 = t 2 ln 2 ln      2 = t 180        t = sec 120 180    | JEE MAIN-2020 | DATE : 05-09-2020 (SHIFT-1) | PAPER-1 | OFFICIAL PAPER | CHEMISTRY PAGE # 4

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