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.