IMAT Chemistry Practice Exam

Ksp is the equilibrium constant for the dissolution of a sparingly soluble salt. When a solid dissolves, it establishes an equilibrium with its ions in solution: the solid → the ions. The solubility product is defined as the product of the activities of the ions in solution at that equilibrium. For dilute solutions, activities are well approximated by concentrations, so Ksp ≈ [M^+][X^−] for a 1:1 salt, or the appropriate product for other stoichiometries (and it depends only on temperature). This means Ksp describes how saturated the solution is with respect to that salt at a given temperature. It is not a rate constant for precipitation, nor is it simply the total amount that can dissolve (solubility), though it is related: higher Ksp generally indicates greater solubility for salts with that stoichiometry. Temperature can change Ksp, reflecting how solubility shifts with heat. So the statement that best defines Ksp is that it is the equilibrium constant for the dissolution process of a sparingly soluble salt.