Chemistry 112

Solubility Rules for Ionic Compounds in Water at 25 °C

1. Salts with Group 1 or ammonium ion (NH₄⁺) as the cation will be soluble.

2. Salts with nitrate (NO₃^–), chlorate (ClO₃^–), perchlorate (ClO₄^–), bicarbonate (HCO₃^–), or acetate (C₂H₃O₂^–) as the anion will be soluble.

3. Halide (Cl^–, Br^–, I^– and less often F^–) salts are soluble except for Pb²⁺, Ag⁺, Hg₂²⁺, Hg²⁺, and Cu⁺.

4. Sulfate (SO₄^2–) salts are soluble except for Ba²⁺, Sr²⁺, Pb²⁺, Hg₂²⁺, and Ag⁺. CaSO₄ is a borderline case, usually considered sparingly soluble.

5. Sulfide (S^2–) and hydroxide (OH^–) salts are sparingly soluble except for rule 1. The sulfides and hydroxides of Ca²⁺, Ba²⁺, and Sr²⁺ are borderline cases, usually considered sparingly soluble.

6. Carbonate (CO₃^2–) and phosphate (PO₄^3–) salts are sparingly soluble except for rule 1.