Answer:
21.86 grams
Explanation:
It is important to note that for every mol of Na3PO4 there is, 3 mols of Na ions are produced.
Na+=1m(0.4l), so mols of Na3PO4= 0.4/3= 0.13333... mols
the molar mass of Na3PO4 is 163.94 grams/mol. 0.1333*163.94=21.86 grams of Na3PO4.