What is a solubility product constant (Ksp)?

The solubility product constant, often denoted as Ksp, specifically pertains to the equilibrium conditions of sparingly soluble ionic compounds in a saturated solution. It reflects the extent to which a solid ionic compound can dissolve in water to form ions. In an equilibrium state, the concentration of ions in solution is multiplied together, each raised to the power of its respective coefficient from the balanced dissolution equation, yielding the Ksp value.

For example, consider a generic sparingly soluble salt, AB, that dissociates into A⁺ and B⁻ ions in solution. The dissolution can be represented as:

[ AB(s) \rightleftharpoons A^+(aq) + B^–(aq) ]

The Ksp expression for this equilibrium would be:

[ Ksp = [A^+][B^-] ]

Where [A⁺] and [B⁻] are the molar concentrations of the ions in the saturated solution. Ksp is unique to each compound at a given temperature and serves as a quantitative measure of how much of an ionic compound can dissolve in a specific volume of solvent. This makes B the correct answer, as it specifically describes the equilibrium relationship of a sparingly soluble ionic compound in a