What is chemical equilibrium?

Chemical equilibrium is defined as a state in a reversible reaction where the rates of the forward and reverse reactions are equal. This means that although both reactants and products are present, their concentrations remain constant over time because the processes of formation and consumption occur at the same rate.

At this point, neither the reactants nor the products are favored; the system remains in a dynamic balance, leading to an equilibrium constant that can quantitatively describe the ratio of products to reactants at this state. Understanding this principle is crucial because it explains many reactions’ behavior in different conditions, such as changes in concentration, temperature, and pressure, which can shift the equilibrium position according to Le Chatelier's principle.

In contrast, having only reactants present indicates that a reaction has not yet proceeded towards equilibrium. Similarly, stating that reactants are completely converted to products describes a completion scenario, which is not characteristic of equilibrium since, by that stage, the system would have reached a constant state with no further changes. Lastly, the decomposition of products does not describe equilibrium but rather an instance where the reaction is moving away from its stabilized state.