Identify the true statement about the concentrations of A and B once the reaction A ⇌ B has reached equilibrium. (a) The concentration of A equals the concentration of B. (b) The concentrations of A and B are constant. (c) The concentration of A decreases and the concentration of B increases. (d) The concentration of B decreases and the concentration of A increases.

Verified step by step guidance

1. Step 1: Understand the concept of chemical equilibrium. At equilibrium, the rate of the forward reaction equals the rate of the reverse reaction, meaning the concentrations of reactants and products remain constant over time.
2. Step 2: Analyze each statement in the context of equilibrium. Statement (a) suggests that the concentrations of A and B are equal, which is not necessarily true at equilibrium unless the equilibrium constant dictates it.
3. Step 3: Evaluate statement (b). At equilibrium, the concentrations of A and B are indeed constant, as the rates of the forward and reverse reactions are equal.
4. Step 4: Consider statement (c). This describes a scenario where the reaction is still proceeding towards equilibrium, not a state of equilibrium itself.
5. Step 5: Assess statement (d). Similar to statement (c), this describes a non-equilibrium state where the reaction is still shifting towards equilibrium.