What occurs when a reaction is in equilibrium?

When a reaction is in equilibrium, it is characterized by the state where the rates of the forward and reverse reactions become equal. This balance means that the amount of reactants being converted to products is happening at the same rate as the amount of products being converted back into reactants. Consequently, while the concentrations of the reactants and products remain constant over time, it does not imply that the reaction has stopped; instead, both reactions continue to occur simultaneously at equal rates.

This concept is crucial in understanding chemical dynamics and the nature of reversible reactions. At equilibrium, the system has reached a state of balance, allowing for dynamic changes without altering the overall concentrations of the substances involved. This helps clarify why some options, such as the idea that the reaction stops completely or that reactants are completely used up, do not reflect the true nature of equilibrium. In truth, at equilibrium, there is still activity in the system, even though the observed concentrations remain constant.