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Calculate the mass of sodium phosphate required to prepare 1.75 L of solution in which the sodium ion concentration is 0.25 mol/L

2 answers

The units given are in mol/L or M

Solve for moles:

0.25mol/L= x moles/1.75L

Solve for x moles:

x moles=1.75L*(0.25mol/L)

x moles * molecular weight of sodium phosphate (163.94 g/mol)= mass or Sodium Phosphate

No more than two significant figures in answer.
I believe the answer provided by this solution is three times too large. The problem asks for grams Na3PO4 to provide 0.25 M SODIUM ION. Since there are 3 Na ions per Na3PO4 molecule you need to divide 0.25/3 to begin with, then proceed s in the above.