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 675 mL of a solution that has a concentration of Na+ ions of 0.800 M ?

Express your answer to three significant figures and include the appropriate units

Answer 1

Given,

Volume of solution = 675 mL x ( 1L/1000 mL) = 0.675 L

Concentration of Na⁺ ions = 0.800 M

Calculating the number of moles of Na⁺ ions in the solution,

We know, the formula to calculate molarity,

Molarity = Number of moles / L of solution

Rearranging the formula,

Number of moles = Molarity x L of solution

Number of moles = 0.800 M x 0.675 L of solution

Number of moles = 0.54 mol Na⁺ ions

Now, calculating the number of moles of Na₃PO₄ required,

= 0.54 mol Na⁺ ions x ( 1 mol Na₃PO₄ / 3 mol Na⁺ ions)

= 0.18 mol Na₃PO₄

Converting number of moles to grams,

= 0.18 mol Na₃PO₄ x (163.94 g / 1 mol)

= 29.5 g of Na₃PO₄