Which statement is true about dynamic equilibrium?

Which statement is true about dynamic equilibrium?

• A. The forward rate is zero.
• B. The reverse rate is zero.
• C. The forward and reverse rates are equal, and concentrations remain constant.
• D. The concentrations of reactants always decrease.

Answer: (C)

Dynamic equilibrium occurs when the forward and reverse rates of a reversible reaction are equal, so the concentrations of reactants and products remain constant over time. Even though both directions are continually occurring, the two rates balance each other, yielding no net change in composition at a given temperature. The rates are not zero; both directions proceed, but their speeds are matched. If conditions like temperature or concentration of a species change, the equilibrium can shift, but under fixed conditions the concentrations stay constant. The other statements would imply one direction has stopped or that reactant concentrations must always fall, which isn’t the case at equilibrium.

Dynamic equilibrium occurs when the forward and reverse rates of a reversible reaction are equal, so the concentrations of reactants and products remain constant over time. Even though both directions are continually occurring, the two rates balance each other, yielding no net change in composition at a given temperature. The rates are not zero; both directions proceed, but their speeds are matched. If conditions like temperature or concentration of a species change, the equilibrium can shift, but under fixed conditions the concentrations stay constant. The other statements would imply one direction has stopped or that reactant concentrations must always fall, which isn’t the case at equilibrium.