A solubility equilibrium is established when the dissolution of a solute
$$ A\,(s) \rightarrow A\, (aq)$$
and its precipitation
$$ A\, (aq) \rightarrow A \,(s)$$
are each occurring at equal rates.
$$ A \,(s) \rightleftharpoons A\, (aq)$$
Solubility describes how much of a compound will dissolve — in other words, how far this equilibrium will proceed.
Solubility equilibria are important to many processes, ranging from tooth decay to water purification. Understanding the factors affecting solubility is essential to managing these processes. We will use the equilibrium concepts and tools learned in the previous chapter to describe and predict solubility behaviour.