Chapter 4, Problem 4.34P

One way to analyze a sports drink for the concentration of chloride ions is to add silver ions and weigh the resulting AgCl precipitate. One problem with the analysis is that many sports drinks contain phosphate ion $\left({\text{PO}}_{\text{4}}{}^{\text{3}-}\right)$ , which will also precipitate with silver, thus interfering with the chloride measurement. The phosphate ion can be removed by precipitation prior to the analysis of chloride.
(a) Use the solubility guidelines (Table 4.2) to choose a cation from the list below that would form a precipitate with phosphate but not with chloride.
${\text{K}}^{+},{\text{ Ba}}^{\text{2}+},{\text{ Pb}}^{\text{2}+},{\text{ NH}}_{\text{4}}{}^{+}$
(b) Write the net ionic reaction for the precipitation reaction from part (a).