Equilibria

Equilibrium can also exist in between the same species in two different forms e.g. liquid and solid, liquid and gas. An equilibrium constant may also be produced for every of these systems.

Conditions of equilibrium

For the general reaction:

aA+bB→cC+dD

The change in Gibbs free energy, ΔG (see Topic B6) for the reaction at a temperature, T, is given by:

Where Q is the reaction quotient,

The free energy change of both the reverse and the forward reaction is equal. This is when ΔGback=ΔG=0. In this case, the rate constants for the forward and back reactions, kf and kb, and the activities of reactants and products are such that both forward and reverse reactions are occurring at an equal rate and the reaction is at equilibrium.