At 25°C, a saturated barium sulfate solution has [Ba²⁺] = [SO₄²⁻] = 1.0 × 10⁻⁵ M. What is Ksp for BaSO₄?

Core Concept

Barium sulfate releases one Ba²⁺ and one SO₄²⁻ per formula unit, so Ksp = [Ba²⁺][SO₄²⁻]. In a saturated solution each ion equals the molar solubility s = 1.0 × 10⁻⁵ M. Multiplying the two equal factors gives (1.0 × 10⁻⁵)(1.0 × 10⁻⁵) = 1.0 × 10⁻¹⁰. The undissolved solid never enters the expression.