How does pH affect solubility equilibria?

1 Answer
Apr 26, 2015

pH usually only affects solubility equilibria in the case where the ions formed by the solubility of the solid are conjugate acids or bases. For example, CaCO3(s) ionizes into Ca+2 and CO3-2, and since CO3-2 can get protonated in acidic conditions to HCO3-1 and H2CO3, then acidic conditions basically remove CO3-2 from solution and increase solubility of CaCO3 (in a Le Chatleir's Principle sort of way).

AgCl ionizing into Ag+ and this case, neither of the ions formed care about H+ (Cl- won't protonate back to HCl), so low pH doesn't affect this solubility.