What is the value of when a system is at equilibrium?
Gibbs free energy: Gibbs free energy is that thermodynamic quantity the decrease in whose value during a process is equal to the maximum possible useful work that can be obtained from the system.
Mathematically it can be represented as follows:
;
where is the change in Gibbs free energy, T is the temperature, is the change in enthalpy, change in entropy.
The usefulness of Gibbs free energy:
Hence, the change in Gibbs free energy is zero at equilibrium.