What is the solubility?

Question

What is the solubility of Cr(OH)₃ at a pH of 10.00? (Ksp Cr(OH)₃ is 6.70 × 10⁻³¹)

Answer 1

Kar,

You have asked many, many, many questions dealing with Ksp and solubility. I have answered many, many of them. I will answer this one as well, but I sure hope you are getting the hang of it, and that you can do them by yourself in the future.

Cr(OH)₃(s) <==> Cr³⁺(aq) + 3OH^-

Ksp = [Cr³⁺][OH^-]³

From the pH value of 10.00, we can find the OH- concentration. Plug that into the Ksp expression and solve for [Cr³⁺]

pH = 10.00 so pOH = 14 - 10 = 4.00

[OH-] = 1x10^-4 M

6.7x10^-31 = [Cr³⁺][1x10^-4]³ = [Cr3+][1.00x10^-12]

[Cr³⁺] = 6.70x10^-19 M = solubility of Cr(OH)₃ at pH 10