# What is Gibbs free energy? How is Gibbs free energy calculated?

Jun 26, 2017

The $\text{Gibbs Free Energy}$ is the single unequivocal criterion for the $\text{spontaneity of chemical change.....}$

#### Explanation:

$\Delta {G}^{\circ} = \Delta {H}^{\circ} - T \Delta {S}^{\circ}$
And thus it includes an $\text{enthalpy term}$, and an $\text{entropy term......}$
The Gibbs free energy is the single, unequivocal criterion for the spontaneity of chemical change. Negative values of $\Delta G$ denote a $\text{spontaneous reaction}$. If $\Delta G = 0$, then the reaction is at equilibrium. And if $\Delta G > 0$ then the reaction is non-spontaneous....
$\Delta G$ may also be related to the equilibrium constant, ${K}_{\text{eq}}$ by the equation:
$\Delta {G}^{\circ} = - R T \ln {K}_{\text{eq}}$.