17. Equilibrium

17. Equilibrium

17.1 The equilibrium law

Nature of science:

• Employing quantitative reasoning - experimentally determined rate expressions for forward and backward reactions can be deduced directly from the stoichiometric equations and allow Le Châtelier’s principle to be applied.

Understandings:

• Le Châtelier’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 Gibbs 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=−RTlnK.

Applications and skills:

• Solution of homogeneous equilibrium problems using the expression for K c.

• Relationship between ∆G and the equilibrium constant.

• Calculations using the equation △G=−RTlnK.