How many grams of Na3PO4 are needed to produce 250mL solution that has an Na concentration of 1.04M?

Answer 1

1.04 M Na = 1.04/3 M Na3PO4 = 0.347
M Na3PO4
M Na3PO4 = mols Na3PO4/L Na3PO4. You know L and M, solve for mols.
Then mol Na3PO4 = grams Na3PO4/molar mass Na3PO4.
You know M