On this page: Under conditions of constant temperature and
pressure, chemical change will tend to occur in whatever
direction leads to a decrease in the value of the Gibbs free
energy. In this lesson we will see how G varies with the
composition of the system as reactants change into products.
When G falls as far as it can, all net change comes to a stop.
The equilibrium composition of the mixture is determined by ΔG°
which also defines the equilibrium constant K. Please see the
All About Equilibrium site for a review of this topic. This
means, of course, that if the total free energy G of a mixture
of reactants and products goes through a minimum value as the
composition changes, then all net change will cease the reaction
system will be in a state of chemical equilibrium. You will
recall that the relative concentrations of reactants and
products in the equilibrium state is expressed by the
equilibrium constant. In this lesson we will examine the
relation between the Gibbs free energy change for a reaction a