What is the pH of a saturated solution of Cd(OH)₂? (Ksp for Cd(OH)₂ = 7.2 × 10⁻¹⁵).

Answer 1

To find the pH, we need to first find the [OH-] from the information provided. Then we can convert this to pOH and then to pH.

Cd(OH)₂(s)<==> Cd²⁺(aq) + 2OH^-(aq)

Kd = 7.2x10^-15

Let x = [Cd²⁺] and then [OH-] = 2x

7.2x10^{-15 =} (x)(2x)² = 4x³

x = 1.8x10^-5 M = [Cd²⁺]

[OH-] = 2 x [Cd²⁺] = 3.6x10^-5 M

pOH = -log [OH-] = 4.44

pH = 14 - pOH

pH = 9.56