In a first-order reaction, the activity of reactant drops from 800 mol/dm^3 to 50 mol/dm^3 in 2 × 10 — Chemical Kinetics Chemistry Question

💡 Solution & Explanation

In a first-order reaction, the concentration ratio is [A]_0/[A]_t = 800/50 = 16 = 2^4. This indicates that 4 half-lives have elapsed. Thus, 4 × t_1/2 = 2 × 10^4 s => t_1/2 = 5000 s. The rate constant is K = ln2/t_1/2 = 0.693/5000 = 1.386 × 10^-4 s^-1.