Question

What is meant by the solubility product for a sparingly soluble salt? Choose a sparingly soluble salt and show how the salt ionizes when dissolved in water, and write the expression for its solubility product.

Short answer

The solubility product (K_sp) is an equilibrium constant for the dissolution of a sparingly soluble salt in water, representing the product of the molar concentrations of the ions, each raised to the power of its stoichiometric coefficient. For example, consider silver chloride (AgCl). When it dissolves in water, it ionizes as follows: \[ AgCl(s) \rightleftharpoons Ag^+(aq) + Cl^-(aq) \] The solubility product expression for AgCl is given by: \[ K_{sp} = [Ag^+][Cl^-] \]

Step-by-step solution

Definition of Solubility Product

Solubility product, denoted as K_sp, is an equilibrium constant for the dissolution of a sparingly soluble salt in water. It is the product of the molar concentrations of the ions formed when a saturated solution of the salt is in equilibrium with its undissolved solid, each concentration raised to the power of its stoichiometric coefficient in the dissolution equation.

Choose a Sparingly Soluble Salt

Let's consider the sparingly soluble salt, silver chloride (AgCl), as our example.

Ionization of the Salt in Water

When silver chloride dissolves in water, it dissociates into its constituent ions, silver (Ag+) and chloride (Cl-), in the following equilibrium reaction: \[ AgCl(s) \rightleftharpoons Ag^+(aq) + Cl^-(aq) \]

Expression for Solubility Product

The solubility product (K_sp) of silver chloride is calculated as the product of the concentrations of the silver and chloride ions, each raised to the power of its stoichiometric coefficient in the dissolution equation. Thus, the solubility product expression for silver chloride can be written as: \[ K_{sp} = [Ag^+][Cl^-] \] Where [Ag+] and [Cl-] represent the molar concentrations of silver and chloride ions, respectively, in the saturated solution at equilibrium.