When ΔG is zero, what does this imply about the chemical reaction?

When the Gibbs free energy change (ΔG) is zero, this indicates that the system is in a state of equilibrium. At equilibrium, the rates of the forward and reverse reactions are equal, meaning that there is no net change in the concentrations of the reactants and products over time. In this state, the system has reached a balance where the driving forces of the reactions in both directions are balanced, leading to a stable condition.

In thermodynamic terms, ΔG is a measure of the spontaneity of a process; a negative ΔG suggests that a reaction is spontaneous in the forward direction, while a positive ΔG indicates that the reaction is spontaneous in the reverse direction. When ΔG is zero, it reflects that there is no tendency for the reaction to move in either direction, reinforcing the concept of equilibrium where both reactants and products are present without favoring one side over the other. This is an essential principle in understanding dynamic equilibria in chemical systems.