Question

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 750. mL of a solution that has a concentration of Na+ ions of 1.50 M ?

Answer 1

Solution :-

Lets first calculate the moles of the Na+ using the molarity and volume

moles of Na+ = molarity * volume in liter

                      = 1.50 mol per L * 0.750 L

                      = 1.125 mol Na^+

now using the mole ratio of the Na+ and Na3PO4 lets calculate the moles of the Na3PO4

1.125 mol Na+ * 1 mol Na3PO4 / 3 mol Na+ = 0.375 mol Na3PO4

now lets calculate the mass of the Na3PO4

mass of Na3PO4 = moles * molar mass

                           = 0.375 mol Na3PO4 * 163.94 g per mol

                           = 61.5 g Na3PO4

So the mass of the Na3PO4 needed = 61.5 g