Solubility Products

For the ionization reaction

the equilibrium expression is

.

If the solution is in equilibrium with the salt in the solid state the solution will be saturated (at that temperature). In this case the term [KClO₄] is a constant and can be combined with K. The result is called the solubility product.

This applies only to saturated solutions at a given temperature. For an unsaturated solution the product is less than K_sp.