A white compound has been analyzed and found to contain 43.6 wt. % phosphorous and 56.4 wt. % oxygen. In a separate study it molecular weight has been
found to be 284 g/mol.
What is
the empirical formula of this compound?
Assume exactly 100 g of
the compound, then one has
43.6 g P ÷ 30.974 g/mol P = 1.408 mol of P
56.4 g O ÷ 15.999 g/mol
O = 3.525 mol of O
then the molar ratios
are
1.408 mol ÷ 1.408 mol =
1.000 mol P
3.525 mol ÷ 1.408 mol =
2.503 mol O
and the empirical
formula is P2O5.