Dynamic equilibrium occurs when:

Dynamic equilibrium occurs when:

• A. The reaction has stopped completely.
• B. Forward and reverse reactions occur at the same rate.
• C. The concentrations of reactants increase while products decrease.
• D. Temperature remains constant as reactions proceed.

Answer: (B)

Dynamic equilibrium is reached when the forward and reverse reactions occur at the same rate, so the overall concentrations of reactants and products remain constant even though molecules keep transforming in both directions. The idea is a balance: as fast as reactants form products, products convert back to reactants at the same rate, creating no net change. The other ideas miss this balance. If the reaction had stopped completely, there would be no ongoing transformation at all, which isn’t dynamic equilibrium. If reactant concentrations were continually increasing while product concentrations decreased, the system wouldn’t have reached a balance of rates. Temperature staying constant is necessary to study equilibrium, but it doesn’t define dynamic equilibrium—the defining feature is equal forward and reverse rates at a fixed temperature.

Dynamic equilibrium is reached when the forward and reverse reactions occur at the same rate, so the overall concentrations of reactants and products remain constant even though molecules keep transforming in both directions. The idea is a balance: as fast as reactants form products, products convert back to reactants at the same rate, creating no net change.

The other ideas miss this balance. If the reaction had stopped completely, there would be no ongoing transformation at all, which isn’t dynamic equilibrium. If reactant concentrations were continually increasing while product concentrations decreased, the system wouldn’t have reached a balance of rates. Temperature staying constant is necessary to study equilibrium, but it doesn’t define dynamic equilibrium—the defining feature is equal forward and reverse rates at a fixed temperature.