01Ksp
A slightly soluble salt reaches equilibrium with its ions: AgCl(s) ⇌ Ag⁺ + Cl⁻, Ksp = [Ag⁺][Cl⁻]. Molar solubility s is how many mol/L dissolve.
For AB₂: Ksp = s(2s)² = 4s³.
02Notebook box
Compare Ksp directly only for salts with the same ion ratio.
Worked example: Ksp(AgBr) = 4.9 × 10^−13 → s = √Ksp = 7.0 × 10^−7 M.