At equilibrium for a simple reaction, what is true about the forward and reverse rates?

At equilibrium for a simple reaction, what is true about the forward and reverse rates?

• A. They are equal
• B. The forward rate is always greater
• C. The reverse rate is always greater
• D. They are never equal

Answer: (A)

At equilibrium for a simple reversible reaction, the forward and reverse rates are equal, so there is no net change in the amounts of reactants and products. Even though both directions keep happening, the rate of A turning into B matches the rate of B turning back into A. This balance can be written as rate_forward = rate_reverse, and for an elementary step A ⇌ B translates to k_f [A] = k_r [B]. The concentrations themselves need not be equal; instead, their ratio is fixed by the equilibrium constant K_eq = [B]/[A] = k_f/k_r. If conditions are disturbed, the system shifts to restore the equality of rates.

At equilibrium for a simple reversible reaction, the forward and reverse rates are equal, so there is no net change in the amounts of reactants and products. Even though both directions keep happening, the rate of A turning into B matches the rate of B turning back into A. This balance can be written as rate_forward = rate_reverse, and for an elementary step A ⇌ B translates to k_f [A] = k_r [B]. The concentrations themselves need not be equal; instead, their ratio is fixed by the equilibrium constant K_eq = [B]/[A] = k_f/k_r. If conditions are disturbed, the system shifts to restore the equality of rates.