[velinos]

First prepare a stock solution that is 1.00 x 10-2 M in phosphate ion. How many g of Na3PO4 would you add to a 250 mL volumetric flask to to prepare this solution?
Mass Na3PO4: .40985

What I did: .01 M X .25 L X 163.94(FW) = .40985g

What is this concentration in ppm of phosphate? (That is as PO43−, not Na3PO4).
PO43− concentration: = 237.425 ppm

What I did: .01 M X .25 L X 94.97(FW) X 1000


I don't understand where I went wrong. Any helpful hint is appreciated.

[ARGOS++]

Dear velinos;

Why you also multiply with 0.25 to get ppm?

Good Luck!
                    ARGOS⁺⁺

[velinos]

Ah! I see my error.

Thank you very much for the response!