Q:

Why does the position of equilibrium depend only on the relative Gibbs energies of the products and the reactants?

The position of equilibrium, I read, is dependent only on the relative Gibbs energies of the products and the reactants. Why is this so? Surely one must take into account the entropy of mixing of the products and the reactants, which wouldn't be dependent on the Gibbs energies, to work out the lowest point (energy wise) and find the position of equilibrium. Why, therefore, is the position of equilibrium between products and reactants only dependent on the relative gibbs energies of the products and reactants.
Thanks!

A:

I quote Wikipedia:

In thermodynamics the entropy of mixing is the increase in the total entropy when several initially separate systems of different composition, each in a thermodynamic state of internal equilibrium, are mixed without chemical reaction by the thermodynamic operation of removal of impermeable partition(s) between them, followed by a time for establishment of a new thermodynamic state of internal equilibrium in the new unpartitioned closed system.

It seems to me that the scenario which you describe is an already mixed solution of reactants. So you have already maximized the entropy, because for every molecule that changes according to the reaction, you get the new molecule at the same place. The overall entropy with respect to the mixing doesn't change.
Note that the position of the equilibrium is only then dependent on the relative gibbs free energies when the reaction is not kinetically hindered (when the activation energy barrier is low enough to be overcome).

