Besides temperature, ionic strength, and common ion effect, the pH of a solution can also have a large impact on solubility whenever one (or both) of the dissociated ions from a solid can act as a weak acid/base. Consider the series of simultaneous equilibria shown below (you can assume all species are aqueous unless otherwise noted): CaF2(s) ⇌ Ca2++ 2F-
Ca2++ F-⇌ CaF+
CaF2(s) ⇌ CaF2(aq)
Ca2++ H2O ⇌ CaOH++ H+
F -+ H+ ⇌ HF
HF + F- ⇌ HF2-
H2O ⇌ H+ + OH-
(a) Write the charge-balance expression for this system.
(b) Write the mass-balance expressions for this system.