[Shasha]

Hi...
I really need some help on this question.

How many grams of potassium phosphate are needed to be added to 55.000mL of water so that the final concentration of the potassium ions will be 0.100 M?

I started off by finding the molar mass of Potassium sulfate which is:
Mm: 212.27 g/mol if I did that correctly.
It then said that the volume is 55ml=0.055L and concentration is 0.100M
So I solved for the number of moles which is:
C=n/v
1.00M=n/0.055L and i got the answer 0.0055? which is really low.
Then since i have the n I can find the mass to be:
n=mass/molar mass
0.0055=x/212.27g/mol and I get the mass to be 1.17 g.
BUT ITS NOT THE RIGHT ANSWER..lol what am i doing wrong??
I would really appreciate an answer.Thanks alot

[Borek]

You are close. How many moles of potassium in one mole of potassium phosphate?