Take a sample of 100 g. 80g C and 20g H.
mols C= 80/12 = 6.667
mols H= 20/1 = 20
Divide both by the smaller; i.e.,
6.6676/667 = 1
20/6.667 = 3
empirical formula is CH3 and empirical mass is 15.
p*M1 = d1RT and (pressure*molar mass = density*RT
p*M2 = d2RT
M1 is molar mass O2;M2 is molar mass compound.
Divide eqn 1 by eqn 2 to obtain
32/M2 = 1.032/0.963. P, R, T cancel
M2 = 32 x 0.963/1.032 = 29.98 = about 30
Then empirical mass x a number = molarmass
15 x ? = 30 and the number is 2 so
(CH3)2 or C2H6 is the molecular formula.
A gaseous compound is composed of 80.0% carbon and 20.0% hydrogen by mass. Its density is 0.963 g/L. The density of oxygen gas at the same temperature and pressure is 1.032 g/L. Determine the molecular formula of the compound
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