Final answer:
The composition of an equilibrium mixture is determined by ΔGθ, as it shows whether a reaction is spontaneous, and any deviation from ΔGθ being zero will cause the reaction to adjust to reach equilibrium, altering the mixture's composition.
Step-by-step explanation:
The composition of an equilibrium mixture depends on the value of ΔGθ because this value indicates whether the reaction can occur spontaneously under standard conditions. At equilibrium, ΔGθ equals zero, which means there is no further net change in the composition of the reaction mixture.
If ΔGθ were to be different from zero, the reaction would either proceed forward or reverse to reach equilibrium, altering the composition of the mixture accordingly.
The equilibrium constant (Keq) is also temperature-dependent, which means that the value of ΔGθ and hence the position of the equilibrium will change with temperature changes, causing shifts in equilibrium.
For instance, if the temperature increases and the reaction is endothermic, the equilibrium will shift to the right, increasing the amount of products in the mixture.