Ionic Equilibria between Solids and Solutions

The sparingly soluble salt silver chloride, for example, establishes the following equilibrium when placed in water  

The equilibrium law for this reaction (written by following the rules for heterogeneous equilibria from Sections 14.2 and 14.3) is 

The molar solubility of a salt in water is not the same as its solubility product constant, but a simple relation often exists between them. For example, let s define S 

Taking the square roots of both sides of the equation gives 

Solubility product constants (like solubilities) can be sensitive to temperature. At 100°C the Ksp for silver chloride is 2.2 X 10 hot water dissolves about 12 times as much silver chloride as does water at 25°C. Refer to Table 16.2 for the solubility product constants at 25°C of a number of important sparingly soluble salts. 

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