A scientist wants to make a solution of tribasic sodium phosphate, Na3PO4, for a laboratory experiment. How many grams of Na3PO4 will be needed to produce 400 mL of a solution that has a concentration of Na+ ions of 1.00 M?

Answer 1

You want how many moles Of Na^+? That is M x L = 1.00 x 0.400 L = 0.400 moles.
How many moles of Na3PO4 will that be? Since there are 3 Na^+ to 1 molecule Na3PO4, 1/3 x 0.400 will be the moles Na3PO4 needed = ??
moles Na3PO4 = grams Na3PO3/molar mass Na3PO4.
Solve for grams.