An aqueous solution contains 0.010 M Mg2+ and 0.010 M Zn2+ ions. The solubility-product constants at 25 °C are Ksp(Mg(OH)2)=1.8×10−11 and Ksp(Zn(OH)2)=3.0×10−17. Consider gradually adding a strong base so that the pH is increased from 7.00 to 12.00.
(a) Describe qualitatively which cation will begin to precipitate first as the pH is raised and explain your reasoning using the numerical information provided.
(b) Explain, without performing detailed calculations, why the other cation remains largely in solution while the first precipitate forms.
(c) At very high pH values, predict what will eventually happen to the second cation and justify your prediction in terms of the relevant equilibrium constant.