Gibbs free energy

In thermodynamics the Gibbs free energy is a state function of any system defined as

G = H - T S

where:

• H is the enthalpy
• T is the temperature
• S is the entropy

The Gibbs free energy is one of the most important thermodynamic functions for the characterisation of a system.

The Gibbs free energy determines outcomes such as the voltage of an electrochemical cell, and K, the equilibrium constant for a reversible reaction. Any natural process occurs if and only if the associated change in G for the system is negative, i.e. the energy of the system decreases.

See also free energy.