Question

what is true of a reaction that has reached equilibrium?
the rate of the forward reaction is greater than the rate of the reverse reaction.
the reaction rate is zero.
the rate of the forward reaction is less than the rate of the reverse reaction.
the reaction rates of the forward and reverse reactions are equal.

Explanation:

• When a reaction reaches equilibrium, it is a dynamic state.
• In this state, the forward and reverse reactions are still occurring.
• But the rate at which the forward reaction proceeds is equal to the rate at which the reverse reaction proceeds.
• If the rate of the forward reaction was greater than the reverse ($\text{rate}_{forward}>\text{rate}_{reverse}$), the reaction would still be moving forward (not at equilibrium).
• If $\text{rate}_{forward}<\text{rate}_{reverse}$, the reaction would be moving in the reverse direction (not at equilibrium).
• The reaction rate is not zero at equilibrium. Reactants are constantly being converted to products and vice - versa.

Answer:

The reaction rates of the forward and reverse reactions are equal.