# How does enthalpy affect the spontaneity of a reaction?

Oct 3, 2015

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

#### Explanation:

Spontaneity is governed by free energy $\Delta G$. The relationship between the change on free energy $\Delta G$ and change on enthalpy $\Delta H$ is:

$\Delta G = \Delta H - T \Delta S$
where $\Delta S$ is the change on entropy.

For spontaneous processes, $\Delta G$ has to be negative. In order to predict the sign of $\Delta G$, we will need to watch for the sign of $\Delta H$ and the term $T \Delta S$. Here is a table that explains this:

Here is a video that explains this in details;