Answer:
85.5%
Step-by-step explanation:
To get the experimental value, you need to convert 15.0 grams of Na2SO4 to grams of Na3PO4. You do this with stoichiometry.
Convert grams of Na2SO4 to moles with molar mass. Then convert to moles of Na3PO4 with the mole-to-mole ratio according to the balanced chemical equation. Then convert moles of Na3PO4 to grams with the molar mass.
15.0 g Na2SO4 x (1 mol/142.04 g) x (2 Na3PO4/3Na2SO4) x (163.94 g/1 mol) = 11.7 g Na3PO4
Percent Yield = (actual value/experimental value) x 100
Actual Value = 10.0 g
Experimental Value = 11.7 g
10.0g/11.7 g = 85.5%