Upon combustion, a gaseous hydrocarbon yields 0.72 g of water and 3.08 g of CO2. The empirical formula of the hydrocarbon is

Let the empirical formula of the hydrocarbon be CxHy. The combustion reaction is CxHy+(x+y/4)O2→xCO2+y/2H2O ∴xy/2=3.08g/44 g mol−10.72g/18 g mol−1=3.08×180.72×44=74 ⇒x:y=7:8So, the empirical formula of the hydrocarbon is C7H8.