Question

Calculate the solubility (in M) of cobalt(II) hydroxide, Co(OH)2(s) in H2O. Ksp = 1.10×10-16 at a specific temperature.

Answer 1

3.018 x 10⁻⁶ M.

Step-by-step explanation:

• Co(OH)₂ dissociates in solution according to the equation:

Co(OH)₂ → Co²⁺ + 2OH⁻.

∵ Ksp = [Co²⁺][OH⁻]² = (s)(2s)² = 4s³.

∴ 4s³ = 1.10 x 10⁻¹⁶.

∴ s³ = 1.10 x 10⁻¹⁶/4 = 2.75 x 10⁻¹⁷.

∴ s = ∛(2.75 x 10⁻¹⁷) = 3.018 x 10⁻⁶ M.