Question

35 grams of sodium phosphate are mixed with enough water to make 3.5L of solution having a densityof 1.045g/mol. Find the concentration of sodium phosphate in ppm.
Using the same information, find the molarity of the sodium and phosphate ions.

Answer 1

second part:
moles Na3PO4 = grams/molar mass
M = moles/L soln

first part:
mass soln = 3,500 mL x 1.045 g/mL = about 3657.5 g
(Note: I think you meant to type 1.045 g/mL for the density and not g/mol).
So the solution is 35 g in 3657.5 g
That is 35/3657.5 = about 0.0096 g/g (but you need to do it more accurately). Multiply both numerator an denominator by 1E6 to obtain ppm.