What is the solubility of Cr(OH)₃ at a pH of 9.70? (Ksp Cr(OH)₃ is 6.70 × 10⁻³¹)

Answer 1

Cr(OH)3 ==> Cr³⁺ + 3OH^-

Ksp = [Cr³⁺][OH]³

pOH = 14 - 9.7 = 4.3

[OH-] = 5x10^-5 M

6.70x10^-31 = [Cr³⁺][5x10^-5]³

[Cr³⁺] = 6.70x10^-31 / [5x10^-5]³

[Cr³⁺] = 4.5x10^-17 M = molar solubility of Cr(OH)₃