ABSTRACT
Under one particular condition, the free energy change of both the forward and the reverse reaction is equal. This is when ∆Gback=∆G=0. In this case, the rate constants for the forward and back reactions, kf and kb, and the activities (and the concentrations, see Topic D1) of reactants and products are such that both forward and reverse reactions are occurring at an equal rate (see Topic F1):
and the reaction is at equilibrium. At equilibrium, the system is at steady-state (i.e. the activities of reactants and products remain unchanged), but it should be emphasized this does not mean that no reaction is occurring. Rather, as the rates of the forward and backward reactions are equal, the disappearance of reactants due to the forward reaction is exactly balanced by their appearance due to the backward reaction. This dynamic condition is usually emphasized by using half-headed arrows, i.e.
