is an equilibrium expression for a chemical equation that represents the dissolving of an ionic compound

Ksp = The product of the concentration of a salt’s ions in a saturated solution, each raised to the appropriate power.

A large Ksp means that the compound is very soluble (forward reaction is favored)

A small Ksp means the compound is not very soluble (reverse reaction is favored)

Ksp is a measure of solubility; it is not actual solubility (as in grams per liter). We can compute the how much will dissolve from the Ksp value.

Steps to determine how much will dissolve• Write the equation for the reaction• Write the Ksp expression• Get Ksp from the table• Take the appropriate root• Convert to grams/liter

Take the appropriate root

• 2.5x10-5 = [Mg2+] [CO32-]

• [Mg2+] = [CO32-] = 5.0x10-

3M

Convert to grams/liter

• (5.0x10-3 mol/L)(84.32 g/mol) =

0.42 g/L

How many grams of MgCO3 can be dissolved in 1.00 L of water if at 50°C, the Ksp = 2.5x10-5?

Take the appropriate root

• 3.7x10-19 = [Fe3+] [S2-]

• [Fe3+] = [S2-] = 6.1x10-10M

Convert to grams/liter

• (6.1x10-10 mol/L)(87.92 g/mol) =

5.4x10-8 g/L

How many grams of FeS will dissolve per liter if at 44°, the Ksp = 3.7x10-19?

How many grams of AgBr can be dissolved in 2.00 L of water if at 20°C, the Ksp = 4.8x10-13?

How many grams of Ca(OH)2 will dissolve in one liter of water if at 15°C, the Ksp = 1.3x10-6?