What is the solubility of Cr(OH)₃ at a pH of 10.10? (Ksp Cr(OH)₃ is 6.70 × 10⁻³¹)

Answer 1

Cr(OH)₃(s) <==> Cr³⁺(aq) + 3OH^-(aq)

Ksp = [Cr³⁺][OH^-]³

pH = 10.10

pOH = 14 - 10.10 = 3.90

[OH^-] = 1x10^-3.90 = 1.26x10^-4 M

Ksp = 6.70x10^-31 = [Cr³⁺][1.26x10^-4]³

6.70x10^-31 = 2x10^-12[Cr³⁺]

[Cr³⁺] = 3.35x10^-19 M = solubility of Cr(OH)₃