Ksp: Calculate from Solubility (mol/L)

Question

A student measures the Pb²⁺ concentration in a saturated aqueous solution of lead hydroxide to be 4.02×10^-6 M.

Based on her data, the solubility product constant for lead hydroxide is ______.

Answer 1

Pb(OH)₂(s) <===> Pb²⁺(aq) + 2OH^-(aq)

If [Pb²⁺] = 4.02x10^-6 M, then [OH^-] must be 2 x 4.02x10^-6 M = 8.04x10^-6 M

Ksp = [Pb²⁺][OH^-]²

Ksp = (4.02x10^-6)(8.04x10^-6)²

Ksp = 2.6x10^-16