What is the Ksp?

Question

If it takes 0.048 g BaF₂ in 15.0 mL of water to make a saturate solution  of BaF₂, calculate its K_sp.

Answer 1

BaF₂(s) <==> Ba²⁺(aq) + 2F^-(aq)

Ksp = [Ba²⁺][F^-]²

The molar mass of BaF2 = 175.3 g/mol

molar concentration of the saturated solution = 0.048 g x 1 mol/175.3 g = 2.7x10^-4 moles/0.015 L = 1.8x10^-2 M

[Ba²⁺] = 1.8x10^-2 M

[F-] = 2 x 1.8x10^-2 M = 3.6x10^-2 M

Ksp = (1.8x10^-2)(3.6x10^-2)²

Ksp = 2.3x10^-5