Question

At a certain temperature, the solubility of strontium arsenate, sr3(aso4)2, is 0.0480 g/l. what is the ksp of this salt at this temperature?

Answer 1

Given the solubility of strontium arsenate is 0.0480 g/l . we have to convert it into mol/L by dividing it over molar mass (540.7 g/mol)
Molar solubility = 0.0480 / 540.7 = 8.9 x 10⁻⁵ mol/L
Dissociation equation:
Sr₃(AsO₄)₂(s) → 3 Sr²⁺(aq) + 2 AsO₄³⁻(aq)
                             3 s                   2 s
Ksp = [Sr²⁺]³ [AsO₄³⁻]²
       = (3s)³ (2s)²
       = 108 s⁵
Ksp = 108 (8.9 x 10⁻⁵) = 5.95 x 10⁻¹⁹