excess Gibbs free energy

thermodynamics

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June 26, 2026

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In thermodynamics, Gibbs free energy (G) is a thermodynamic potential used to describe open systems at constant temperature and pressure. It represents the maximum amount of non-expansion work that can be extracted from a thermodynamically closed system. The change in Gibbs free energy (\u0394G) indicates the spontaneity of a process: a negative \u0394G signifies a spontaneous process, while a positive \u0394G indicates a non-spontaneous process.

The excess Gibbs free energy (G^E) specifically quantifies the deviation of a solution's Gibbs energy from that of an ideal solution. It is related to activity coefficients, which measure how much a solution differs from ideal behavior. The excess Gibbs free energy is composed of excess enthalpy (H^E) and excess entropy (S^E), reflecting intermolecular forces and disorder, respectively.123456

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Activity coefficients and excess functions
…designated by G^E, called the excess Gibbs (or free) energy. The significance of the word excess lies in the fact that G^E is the Gibbs energy of a solution in excess of what it would be if it were ideal.
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…designated by G^E, called the excess Gibbs (or free) energy. The significance of the word excess lies in the fact that G^E is the Gibbs energy of a solution in excess of what it would be if it were ideal.
Read More