Question Detail
Question
The solubility of CaF₂ is 2.0 × 10⁻⁴ M at 25°C. What is the Ksp of CaF₂?
Correct Answer
Option A is the correct answer.
Detailed Explanation
CaF₂(s) ⇌ Ca²⁺(aq) + 2F⁻(aq). If solubility s = 2.0×10⁻⁴ M, then [Ca²⁺] = s, [F⁻] = 2s. Ksp = [Ca²⁺][F⁻]² = s × (2s)² = 4s³ = 4 × (2.0×10⁻⁴)³ = 4 × 8.0×10⁻¹² = 3.2×10⁻¹¹.
Hint
Relate the ion concentrations to the molar solubility using the dissociation equation.