Question

An aqueous solution of lead II phosphate is added to an aqueous solution of potassium iodide. When the two colorless solutions mix, a bright yellow precipitate forms in a double replacement reaction. What is the balanced chemical equation?

Answer 1

`PbHPO_4(aq) + 2KI(aq) rarr PbI_2(s)darr + KH_2PO_4`

Explanation:

This question is unfortunate as phosphate salts tend to be as soluble as bricks, and lead phosphate, `Pb_3(PO_4)_2` would be even more insoluble. Thus I have assumed a biphosphate salt; `HPO_4^(2-)` can have some solubility (at any rate phosphate ion, `PO_4^(3-)`, is fairly rare, and speciates to `HPO_4^(2-)` in aqueous solution).