Barrons SAT Subject Test Chemistry, 13th Edition

(c) The percentage of dissociation of the original acid may be expressed as

Solubility Products

A saturated solution of a substance has been defined as an equilibrium condition
between the solute and its ions. For example:

AgCl(s) Ag+(aq) + Cl−(aq)

The equilibrium constant would be:

TIP

Ksp incorporates the concentration of the solute.

Since the concentration of the solute remains constant for that temperature,
the [AgCl] is incorporated into the K to give the Ksp, called the solubility

constant:

Ksp = [Ag+][Cl−] = 1.2 × 10−10 at 25°C

This setup can be used to solve problems in which the ionic concentrations are
given and the Ksp is to be found or the Ksp is given and the ionic concentrations

are to be determined.

Typical Problem

Finding the Ksp.

By experimentation it is found that a saturated solution of BaSO 4 at 25°C contains

3.9 × 10−5 mole/liter of Ba2+ ions. Find the Ksp of this salt.

Since BaSO 4 ionizes into equal numbers of Ba2+ and SO 4 2−, the barium ion

concentration will equal the sulfate ion concentration. Then the solution is

BaSO 4 (s) Ba2+(aq) + SO 4 2−(aq)