Solubility Equilibra

Question 1

Definition of solubility.

Answer 1

Solubility refers to the maximum amount of solute (mass or mol) that can be dissolved in 1dm3 of solution to form a SATURATED solution. (note: it is a concentration term, e.g. mol dm-3, g dm-3, g cm-3

Question 2

Definition of Ksp, or solubility product.

Answer 2

Ksp is the product of the concentration of dissolved ions (each raised to its appropriate power) in a saturated solution of the salt at a given temperature.

Question 3

Definition of ionic product.

Answer 3

It is the product of molar concentrations of the constituent ions AT THAT INSTANT raised to the appropriate powers at a given temperature.

Question 4

How to find Ksp from solubility?

Answer 4

1. Write the partial dissociation eqn for the sparingly soluble salt.
2. Write the Ksp expression.
3. In an ICE table, calculate the equilibrium concentrations for each ion from the solubility of the compound using MOLE RATIO.
4. Substitute the equilibrium concentrations into the Ksp expression and solve.

Question 5

How to find solubility from Ksp?

Answer 5

1. Let solubility be X mol dm-3.
2. Write the partial dissociation eqn for the sparingly soluble salt.
3. Write the Ksp expression.
4. In an ICE table, determine equilibrium concentrations for each ion from the solubility of the compound using MOLE RATIO, in terms of X.
5. Substitute the equilibrium concentrations into the Ksp expression and solve.