What factors affect solubility of ionic compounds?
Strong solute-solvent attractions increase solubility of ionic compounds. Ionic compounds are most soluble in polar solvents like water, because the ions of the solid are strongly attracted to the polar solvent molecules.
Ionic compounds are less soluble is solvents that contain a common ion. For example, CaSO₄ is slightly soluble in water.
CaSO₄(s) ⇌ Ca²⁺(aq) + SO₄²⁻(aq)
If the water already contains calcium ions or sulfate ions, the position of equilibrium moves to the left and the solubility decreases (Le Châtelier’s Principle).
Increasing the temperature usually increases the solubility of an ionic compound because the solution process is usually endothermic.
CaSO₄(s) + heat ⇌ Ca²⁺(aq) + SO₄²⁻(aq)
Le Châtelier’s Principle predicts that increasing the temperature (adding heat) will shift the position of equilibrium to the right. The compound will become more soluble.