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 550. mL of a solution that has a concentration of Na+ ions of 1.50 M ? Express your answer to three significant figures and include the appropriate units.

Answer 1

We know from the formula that in each mole of Na3PO4 , there are three moles of Na+ ions.

In order to make 1.50 M of 550 ml solution with respect to Na+ ions, we need a 550 ml solution of Na3PO4 with a concentration of (1.50 / 3) = 0.5M .

0.5 M concentration means 0.5 moles of Na3PO4 in one liter.

Then the number of moles of Na3PO4 in 550ml solution = 0.275 moles.

We know that Number of moles = weight / molecular weight

since the molecular weight of Na3PO4 = 163.94 g/mol ,

Weight of Na3PO4 = 0.275 x 163.94

= 45.0835 grams.