Determine Ksp given molar solubility

Question

Determine Ksp for the sparingly soluble MgF2, given its molar solubility is 1.2 X 10-3 mol/L

Answer 1

MgF₂(s) <==> Mg²⁺(aq) + 2F^-(aq)

Ksp = [Mg²⁺][F^-]² and since [Mg²⁺] = 1.2x10^-3 M, the [F^-] is 2x that or 2.4x10^-3 M

Ksp = (1.2x10^-3)(2.4x10^-3)²

Ksp = 6.9x10^-9