Final answer:
Salts that contain basic anions will be more soluble at low pH than at high pH. An example of such a salt is CaF₂.
Step-by-step explanation:
The solubility of a salt can be affected by the pH of the solution. In general, salts that contain basic anions will be more soluble at low pH than at high pH. An example of such a salt is CaF₂. In pure water, CaF₂ is sparingly soluble, but in an acidic solution, the fluoride ions from CaF₂ react with the excess H⁺ ions, forming HF.
This reaction removes the fluoride ions from the solution, effectively increasing the solubility of CaF₂. On the other hand, at high pH, the presence of OH⁻ ions can react with the calcium ions from CaF₂, forming an insoluble precipitate of calcium hydroxide (Ca(OH)₂), decreasing the solubility of CaF₂.