The half-life of a zero order reaction is 20 min when the initial concentration of the reactant is 0.4 M . The time required for the concentration of the reactant to drop to 0.1 M is:

Step-by-step solution

For a zero order reaction, the rate constant k is calculated from the half-life as: k = [A]₀ 2t_ 1/2 k = 0.4 M 2 20 min = 0.01 M min ⁻¹ The integrated rate equation for a zero order reaction is: [A]_t = [A]₀ - kt Rearranging to solve for time t : t = [A]₀ - [A]_t k t = 0.4 M - 0.1 M 0.01 M min ⁻¹ = 0.3 0.01 = 30 min Alternatively, since the concentration drops at a constant rate in zero order kinetics, a 0.2 M drop takes 20 min (one half-life), so a 0.3 M drop takes 30 min . Answer: 30 min