Question

I know the basic relation that ΔG=ΔG⁰+RTln(Q) where Q is the reaction quotient, my doubt is that if Q=1 at equilibrium then ΔG=ΔG⁰ but will ΔG=0 or ΔG≠0? As far as I know, generally at equilibrium Q=Keq, ΔG=0.

Answer 1

At equilibrium, ΔG is zero and the reaction quotient Q equals the equilibrium constant K. The relationship ΔG° = -RT ln K describes how the standard free energy change is related to the equilibrium constant. ΔG° indicates the balance of reactants and products at equilibrium.

Step-by-step explanation:

When discussing the relationship between free energy and the equilibrium constant, it is important to note that at equilibrium, ΔG, or the change in Gibbs free energy of the system, is zero. For a reaction at equilibrium, the reaction quotient Q is equal to the equilibrium constant K (whether Kc for concentrations or Kp for partial pressures). This results in the equation ΔG = ΔG° + RT ln Q being simplified to 0 = ΔG° + RT ln K, which is rearranged to give ΔG° = -RT ln K. This indicates that ΔG°, the standard free energy change, is related to the equilibrium constant of the reaction.

If ΔG° is zero, then ln K would also be zero, indicating that K is one and that there is no preference for reactants or products at equilibrium. However, if ΔG° is negative, it implies that K is greater than one, and products are favored; conversely, a positive ΔG° would imply that K is less than one, and reactants are favored. Thus, ΔG° provides information about the position of equilibrium under standard conditions.