CHEMISTRY · Multi-part · AP · Chemistry · Acids and Bases · Acids and Bases
Problem
The three crystalline salts Mg(OH)2(s), Na2SO4(s), and K2HPO4(s) are each sparingly soluble in water. Assume the temperature is 25 °C.
(a) For each salt, predict whether raising the pH of the solution (i.e., making the solution more basic) will increase, decrease, or not change its molar solubility. Present your predictions in a clearly organized table.
(b) For one salt whose solubility you predicted would decrease upon raising the pH, write the net ionic equation that accounts for this effect.
(c) For one salt whose solubility you predicted would increase upon raising the pH, write the net ionic equation that accounts for this effect.
(d) Briefly discuss why Na2SO4(s) behaves differently from the other two salts with respect to pH changes, citing pertinent acid–base properties of the constituent ions.