Let CαHh be the 10‌mL of gaseous hydrocarbon that produces 40‌mL of CO2 and 50‌mL of water So, CaHb+(a+‌
b
4
)O2→aCO2+‌
b
2
H2O ‌10‌mL+‌ excess→‌‌‌0‌‌‌‌0 ‌‌‌‌‌0‌‌‌+‌ excess →‌‌10a‌‌5b Ratio of volume is =10:40:50=1:4:5 All carbon from hydrocarbon is in the CO2. 10‌mL of hydrocarbon produces 40‌mL of CO2. ∴1:4 ratio. So, 1 mole of hydrocarbon has four moles of carbon. 10‌mL of hydrocarbon produces 50‌mL water. i.e. 1 : 5 ratio. Each water molecule has 2 moles of H-atom. So, 1 mole hydrogen carbon compound has 10 moles of hydrogen. ∴ The molecular formula of the hydrocarbon is C4H10.