Question

Calculate the solubility (in M) of cobalt(II) hydroxide, Co(OH)2(s) in H2O. Ksp=3.50×10-16 at a specific temperature.

Answer 1

The solubility equilibrium of Co(OH)2 is:-

Co(OH)2 (s) ↔ Co2+ (aq) + 2OH- (aq)

The solubility product is given as:

Ksp = [Co2+][OH-]²

If 's' is the molar solubility of cobalt(II) hydroxide then we have:

[Co2+] = s

[OH-] = 2s

Ksp = (s)(2s)² = 4s³

3.50*10⁻¹⁶ = 4s³

s =
`\sqrt[3]{3.50*}10^(-16) /4` = 4.49*10⁻⁶ M

Ans: Solubility of Cobalt(II) hydroxide is 4.49*10⁻⁶ M