What factors affect solubility of ionic compounds?
1 Answer
The solubilities of ionic compounds are affected by solute-solvent interactions, the common ion effect, and temperature.
SOLUTE-SOLVENT ATTRACTIONS
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.
COMMON-ION EFFECT
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).
TEMPERATURE
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.
