Which ionic compound(s) listed below would increase in solubility upon lowering the pH?
I. CaF₂
II. Ni(OH) ₂
III. PbCl₂

Question

Which ionic compound(s) listed below would increase in solubility upon lowering the pH? I. CaF₂ II. Ni(OH)₂ III. PbCl₂

Quizplus · Accepted Answer

Ionic compounds that contain anions which can react with H+ (from the increased acidity when pH is lowered) will have their solubility increased. CaF2 and Ni(OH)2 both contain anions (F- and OH-, respectively) that react with H+ to form HF and H2O, thus removing these ions from the solution and driving the dissolution reaction forward according to Le Chatelier's principle. PbCl2, however, does not significantly react with H+ since Cl- is the conjugate base of a strong acid (HCl) and is thus not significantly protonated in acidic solution.

Which Ionic Compound(s) Listed Below Would Increase in Solubility Upon