Determining solubility in aqueous solution?

Question

Determine the solubility at 25 deg. C of Cd(IO3)2 in water and in 0.20 M CdCl2. Ksp of Cd(IO3)2 is 2.4 * 10^-8 at 25 deg. C. How do you do this?

Answer 1

You need to examine the equation for the dissolution of Cd(IO₃)₂.

Cd(IO₃)₂(s) ↔ Cd²⁺(aq) + 2 IO₃^1-(aq)

The solid dissociates producing twice as much IO₃^1- as Cd²⁺. Therefore the equilibrium concentrations of Cd²⁺ = x and IO₃^1- = 2x. Using the Ksp expression [Cd²⁺] * [IO₃^1-]² = 2.4 * 10^-8 plug in x and 2x respectively and solve for x. The solubility of the compound is x.