In the equation ΔG = -RTln(Keq), what is indicated if ΔG is negative?

In the context of the equation ΔG = -RTln(Keq), a negative value for ΔG indicates that the reaction is spontaneous under standard conditions. This spontaneity means that the reaction can proceed in the forward direction without the need for external energy input.

When ΔG is negative, it suggests that the products of the reaction have a lower free energy than the reactants, favoring the formation of products. The term Keq, which is the equilibrium constant, represents the ratio of the concentrations of products to reactants at equilibrium. If the equilibrium constant is greater than 1, then ln(Keq) is positive, making ΔG negative, which aligns with the concept of a spontaneous reaction.

In contrast, if ΔG were zero, the system would be at equilibrium, meaning there is no net change in the concentration of reactants and products. A positive ΔG indicates a non-spontaneous reaction, where external energy would be necessary to drive the reaction forward. Therefore, a negative ΔG effectively correlates with a reaction that can naturally proceed in the direction of product formation.