In a proper equilibrium system, what can be said about the concentrations of reactants and products?

In a proper equilibrium system, the concentrations of reactants and products remain constant over time. This situation arises because the forward and reverse reactions occur at the same rate, leading to a dynamic balance between the concentrations of the reactants and products. Although the concentrations do not change, it is important to note that this does not mean they are equal; they can vary depending on the specific reaction and conditions.

The concept of dynamic equilibrium describes a state where the rate of formation of products from reactants equals the rate of formation of reactants from products. As a result, the system reaches a point where the concentrations appear stable, but molecular activity continues at a molecular level. This equilibrium state ensures that the overall concentrations of the components remain constant even as individual molecules react and transform.

The other options suggest conditions that do not accurately represent chemical equilibrium. For example, stating that concentrations are always equal implies a misunderstanding of the nature of reactions where different stoichiometric coefficients may lead to differing amounts of reactants and products. Indicating that concentrations increase indefinitely overlooks the definition of equilibrium, where changes cease after reaching a balanced state. Lastly, the idea of concentrations fluctuating regularly suggests a lack of stability, which contradicts the concept of a system in equilibrium.