A hydrogen contains `10.5 g` of carbon per gram of hydrogen. If `1 L` of the vapour of the hydrocarbon at `127^(@)C` at `1 atm` pressure weights `2.8 g`, then find the molecular formula of the hydrocarbon.

Explanation

`PV=nRT=(w)/(M)RT`
or `1=(2.8)/(M)xx0.0821xx400`
or `M=91.95~~92`
Let the formula be `C_(a)H_(b)`. So
`12a+b=92`
`(12a)/(b)=10.5` (given)
`11.5b=92`
or `b=8`
`:. a=7`
Therefore, the formula is `C_(7)H_(8)`.