3 MgCl2(aq) + 2 Na3PO4(aq) ==> Mg3(PO4)2(s) + 6 NaCl(aq)

Question

How many milliliters of 0.0800 M Na3PO4(aq) will react with 0.060 mol of MgCl2(aq)?

Answer 1

0.060 mol MgCl2 x (2 mols Na3PO4/3 mol MgCl2) = 0.060 x (2/3) = mols Na3PO4.
Then M = mols/L. You know mols and M, solve for L and convert to mL.