Free Energy and Concentration

Standard state represents a 1M solution. The chemical potential of a component A (G A) is equal to the chemical potential at the standard state plus RT ln[A]

At [A] = 1M, G A = G A

Consider moving molecule A from one side of a membrane through which A can pass (region 1) to the other (region 2).

The free energy of moving A out of region 1 is given by

The free energy of moving A into region 2 is given by

Overall,

Thus, if the concentration of A in region 2 is lower than in region 1, G is negative and the process is favorable. On the other hand, if the concentration of A in region 2 is higher than in region 1, G is positive and the process is unfavorable

See also: Internal energy (E), Enthalpy, Interplay of Enthalpy and Entropy, Important Differences Between G' and