Question

A saturated solution, prepared by dissolving CaF_2(s) in water, has [Ca²⁺] = 3.3 × 10⁻⁴ M What is the K_sp of CaF₂?

Answer 1

\[\ce{CaF2_{(s)} ⇌ Ca^{2+}_{( aq)} + 2F^-_{( aq)}}\]

[F⁻] = 2 [Ca²⁺]

= 2 × 3.3 × 10⁻⁴ M

= 6.6 × 10⁻⁴ M

K_sp = [Ca²⁺] [F⁻]²

= (3.3 × 10⁻⁴) (6.6 × 10⁻⁴)²

= 1.44 × 10⁻⁴