100 mL of a saturated solution of SrF2 contains 0.011 g of SrF2. What is the Ksp of SrF2?

Question

100 mL of a saturated solution of SrF₂ contains 0.011 g of SrF₂. What is the K_sp of SrF₂?

Answer 1

Molar mass SrF₂ = 125.6 g / mol

[SrF₂] = 0.011g x 1mol / 125.6 g = 8.76x10^-5 mols / 0.100 L = 8.76x10^-4 M

SrF₂(s) <==> Sr²⁺(aq) + 2F^-(aq) and [Sr²⁺] = 8.76x10^-4 M and [F-] = 2x8.76x10^-4 M = 1.75x10^-3 M

Ksp = [Sr²⁺][F^-]² = (8.76x10^-4 M)(1.75x10^-3)²

Ksp = 2.69x10^-9

(be sure to check the math)