In a saturated solution of Zn(OH)2 at 25°C, the value of [OH-] is 2.0 x 10-4 M. What is the value of the solubility-product constant, Ksp, for Zn(OH)2 at 25°C ?

Question

In a saturated solution of Zn(OH)₂ at 25°C, the value of [OH^-] is 2.0 x 10^-4 M. What is the value of the solubility-product constant, Ksp, for Zn(OH)₂ at 25°C ?

1. 8.0 x 10^-12

1. 4.0 x 10^-12

1. 2.0 x 10^-4

Answer 1

Zn(OH)₂(s) ==> Zn²⁺(aq) + 2OH^-(aq)

Ksp = [Zn²⁺][OH^-]²

If [OH^-] = 2.0x10^-4, the [Zn²⁺] must = 1.0x10^-4 since there are 2 OH- for each Zn²⁺

Ksp = (1x10^-4)(2x10^-4)²

Ksp = 4x10^-12