Question

An unknown gaseous hydrocarbon contains 85.63 % carbon. If its density is 0.488 g/L at 0.355 atm and 100°C,
what is the molecular formula of the gas?

I can't figure this out. By assuming the total mass to be 100g, I get 85.63g C and 14.37g H which I then used to get the empirical formula of the hydrocarbon, CH2. I just don't know where to take it from here.

Answer 1

Use P*molar mass = density*RT
Solve for molar mass.
Then empicical formula mass x x = molar mass
Solve for x which is
(empirical formula mass)_x which is
(CH2)_x or it can be re-written as
CxH2x for the molecular formula.