Chapter 4, Problem 83E

Hard water often contains dissloved $C{a}^{2+}$ and $M{g}^{2+}$ ions. One way to soften water is to add phosphates. The phosphate ion forms insoluble precipitates with calcium and magnesium ions, removing them from solution. Suppose that a solution is 0.050 M in calcium chloride and 0.085 M in magnesium nitrate. What mass of sodium phosphate must be added to 1.5 L of this solution to completely eliminate the hard water ions? Assume complete reactions.