What does equilibrium indicate in a chemical reaction?

Equilibrium in a chemical reaction signifies a dynamic balance between the concentrations of reactants and products. A key aspect of this state is that the concentrations remain constant over time, indicating that the rate of the forward reaction equals the rate of the reverse reaction. This balance does not necessarily imply that the concentrations of reactants and products are equal; rather, they can be at different levels while still achieving equilibrium.

Different reactions may reach equilibrium with different ratios of products to reactants, depending on the reaction conditions, such as temperature and pressure. It is crucial to understand that equilibrium is a state where there is no net change in the amounts of reactants and products, despite the ongoing nature of the reactions in both directions.

Thus, the correct interpretation of equilibrium is that concentrations remain constant, but they do not have to be equal, making the chosen answer appropriate.