Question #ddcb7

1 Answer
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#


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.