● Le Chatelier’s principle for changes in concentration can be explained by the equilibrium law.
● The position of equilibrium corresponds to a maximum value of entropy and a minimum in the
value of the Gibb’s free energy.
● The Gibbs free energy change of a reaction and the equilibrium constant can both be used to
measure the position of an equilibrium reaction and are related by the equation, G = −RT lnK .
Guidance
● The expression G = −RT lnK is given in the data booklet in section 1.
● Students will not be expected to derive the expression G = −RT lnK.

● Solution of homogeneous equilibrium problems using the expression for Kc.
Guidance
The use of quadratic equations will not be assessed.
● Relationship between G and the equilibrium constant.
● Calculations using the equation G° = RTInk.