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 molecular formula of this compound?
First determine the
empirical weight of P2O5:
2 ´ 30.974 g/mol P = 61.948
g/mol P
5 ´ 15.999 g/mol O = 79.997
g/mol O
The empirical weight of P2O5 = the sum =
141.945 g/mol
Molecular weight ÷ Empirical weight = 284 g/mol ÷ 141.945
g/mol
= 2.001
and the molecular formula is twice the empirical formula and
the molecular formula is P4O10.