A substance 'A' decomposes in solution following first-order kinetics. Flask 1 contains 1 L of 1 M solution of 'A' and flask 2 contains 100 ml of 0.6 M solution of 'A'. After 8.0 h, the concentration

Question

A substance 'A' decomposes in solution following first-order kinetics. Flask 1 contains 1 L of 1 M solution of 'A' and flask 2 contains 100 ml of 0.6 M solution of 'A'. After 8.0 h, the concentration of 'A' in flask 1 becomes 0.25 M. In what time, the concentration of 'A' in flask 2 becomes 0.3 M?

Prashant Kotian · Accepted Answer

Correct answer: C. In Flask 1, [A] goes from 1.0 M to 0.25 M (2 half-lives) in 8.0 h, so t1/2 = 4.0 h. In Flask 2, [A] goes from 0.6 M to 0.3 M, which represents exactly 1 half-life. Since it is a first-order reaction, t1/2 is independent of initial concentration. Time = 4.0 h. Therefore, correct answer is C.

💡 Solution & Explanation

Practice 22,000+ questions like this