Question

In an attempted determination of the solubility product constant of Tl₂S, the solubility of this compound in pure CO₂ free water was determined as 6.3 × 10^–6 mol/L. Assume that the dissolved sulphide hydrolysis almost completely to HS^– and that the further hydrolysis to H₂S can be neglected. What is the computed K_sp? (K₂ = 1.0 × 10^–14) 

Answer 1

[Tl⁺] = 2(6.3 × 10^–6) M, [S^–2] = 6.3 × 10^–6 M, and since [HS^–] = [S^-2] 

[S^2–] = (6.3 × 10^–6)² 

K_sp = (6.3 × 10^–6)² [2(6.3 × 10^–6)]² 

= 6.3 × 10^–21