# Question ddcb7

Nov 17, 2016

Basically, when heat is evolved, entropy is increasing. When heat is absorbed, entropy is decreasing.

A key relationship is the Gibbs Free Energy of Formation:
Delta G = Delta H – t*Delta S#

#### Explanation:

Free energy is the energy available to do work. Thus, if a particular reaction is accompanied by a release of usable energy (that is, if $\Delta G$ is negative), this fact alone guarantees that it is spontaneous.

We can summarize the conditions for spontaneity and equilibrium at constant temperature and pressure in terms of $\Delta G$ as follows:

$\Delta G < 0$ The reaction is spontaneous in the forward direction.
$\Delta G > 0$ The reaction is non-spontaneous. The reaction is spontaneous in the opposite direction.
$\Delta G = 0$ The system is at equilibrium. There is no net change.