In a reversible reaction, equilibrium occurs when

In a reversible reaction, equilibrium occurs when

• A. The forward rate is zero.
• B. The forward and reverse rates are equal.
• C. All reactants are converted.
• D. Only products remain.

Answer: (B)

In a reversible reaction, equilibrium is reached when the forward and reverse reaction rates are equal, so the amounts of reactants and products stay constant over time. This is a dynamic balance: molecules are still moving back and forth between reactants and products, but the two directions occur at the same rate, canceling out so there’s no net change in concentrations. The idea can be seen with A turning into B and B turning back into A; at equilibrium, the rate of A becoming B equals the rate of B becoming A, which sets a stable ratio of A to B that doesn’t change unless temperature or other conditions change. If the forward rate were zero, there would be no ongoing conversion to balance with the reverse direction, so you wouldn’t have both reactants and products present in a steady state. If all reactants were converted, there’d be no source for the forward reaction, and no reverse activity to balance it. If only products remained, there wouldn’t be reactants to convert, so the forward rate wouldn’t match a reverse rate, breaking the equilibrium condition.

In a reversible reaction, equilibrium is reached when the forward and reverse reaction rates are equal, so the amounts of reactants and products stay constant over time. This is a dynamic balance: molecules are still moving back and forth between reactants and products, but the two directions occur at the same rate, canceling out so there’s no net change in concentrations. The idea can be seen with A turning into B and B turning back into A; at equilibrium, the rate of A becoming B equals the rate of B becoming A, which sets a stable ratio of A to B that doesn’t change unless temperature or other conditions change.

If the forward rate were zero, there would be no ongoing conversion to balance with the reverse direction, so you wouldn’t have both reactants and products present in a steady state. If all reactants were converted, there’d be no source for the forward reaction, and no reverse activity to balance it. If only products remained, there wouldn’t be reactants to convert, so the forward rate wouldn’t match a reverse rate, breaking the equilibrium condition.