Gibbs Free Energy

Energy released or absorbed in a reaction occurring reversibly at constant pressure and temperature. Devised by Josiah Willard Gibbs in 1876 to predict whether a process will occur spontaneously at constant pressure and temperature.

A function of the system related to Suniv. It is used to determine the spontaneity of a reaction. It is represented by the symbol G.


G = Gibbs free energy [J]
H = Enthalpy [J]
T = Temperature [K]
S = Entropy [JK-1]

Changes in G correspond to changes in free energy for processes occuring at constant temperature and pressure; the Gibbs free energy change corresponds to the maximum nonexpansion work that can be obtained under these conditions.

The sign of δG is negative for all spontaneous processes and zero for processes at equilibrium.

See also: Helmholtz Free Energy, Internal Energy, Thermodynamic Free Energy.

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Subjects: Chemistry