For a strictly reversible opposing elementary reaction defined as taking place in a closed container — Chemical Kinetics Chemistry Question

💡 Solution & Explanation

Statement A is correct: at equilibrium, $k_f(a - [B]_{eq}) = k_b[B]_{eq}$, which solves to $[B]_{eq} = \frac{k_f a}{k_f + k_b}$, leaving $[A]_{eq} = a - [B]_{eq} = \frac{k_b a}{k_f + k_b}$. Statement B describes the standard integrated rate law for opposing first-order reactions ($k_{eff} = k_f + k_b$). Statement C defines dynamic equilibrium. Statement D is false because, mathematically, $100\%$ completion (or absolute equilibrium) for an exponential first-order decay approach requires infinite time ($t \rightarrow \infty$).