# What does Gibbs free energy mean?

Jan 19, 2017

Essentially it is a measure of how spontaneously a reaction occurs.

#### Explanation:

Gibbs free energy can be viewed as a measure of the "spontaneity" of a reaction (does it occur spontaneously, or not?).

It is defined as the enthalpy (H) minus the product of the temperature and entropy (S).

G = H - TS

The Gibbs Free Energy change $\Delta$G is negative for a spontaneous reaction, and positive for one that is not spontaneous.

$\Delta$G = $\Delta$H - T$\Delta$S

By rearranging the equation for T, and plugging in the various values of $\Delta$H and $\Delta$S it is possible to predict at what temperature the reaction becomes spontaneous.