The solubility of a salt of weak acid increases if the solution is made more acidic (i.e., pH is increased). For example, the solubility equilibrium of CaF2 may be represented as :
\(CaF_2(s)\rightleftharpoons Ca^{2+}(aq) + 2F^-(aq)\)
On making the solution more acidic, H+ ions will combine with the F ions. As a result, equilibrium will shift forward,i.e., solubility will increase.
