Question

What are the products in the following reaction: `?Na_3PO_4(aq) + ?CaCl_2(aq) -> ?NaCl(aq) + ?Ca_3(PO_4)_2(s)`?

Answer 1

`"Calcium phosphate"` and `"sodium chloride"`. Of course there is speciation of the phosphate ion in aqueous solution.

Explanation:

Most phosphates are in fact biphosphates, i.e. salts of `["HPO"_4]""^(2-)`; this is certainly true in aqueous solution, where phosphate ion, `["PO"_4]""^(3-)`, is a powerful Bronsted base:

`"PO"_4""^(3-) + "H"_2"O" rarr "HPO"_4""^(2-) + ""^(-)"OH"`

In solution, your equation probably represents the reaction:

`"Na"_2"HPO"_4(aq) + "CaCl"_2(aq) rarr "CaHPO"_4(s)darr+2"NaCl"(aq)`.

If we keep with the equation as written, we get:

`"Na"_3"PO"_4(aq) + "3CaCl"_2(aq) rarr "Ca"_3("PO"_4)_2(s)darr+2"NaCl"(aq)`.

Which I think is balanced with respect to mass and charge. I do not think that the 2nd reaction reflects chemical reality.