A 13.27 g sample of a compound contains 8.47 g of iron, Fe, 1.57 g of phosphorus, P, and oxygen, O. Calculate the empirical formula for the compound.

Answer 1

Convert grams to moles:

8.47 g Fe x 1 mol Fe / 55.8 g = 0.151 mols Fe

1.57 g P x 1 mol P / 30.97 g = 0.0507 mols P

g O = 13.27 g - 8.47 g - 1.57 g = 3.23 g O x 1 mol O / 16 g = 0.202 mols O

Divide all by 0.0507 to try to get whole numbers:

0.151 / 00507 = 3 mols Fe

0.0507 / 0.0507 = 1 mol P

0.202 / 0.0507 = 4 mols O

Empirical formula = Fe₃PO₄ (don't think this exists)