O2───▸2CO2+3H2O;ΔH=−368 kcal /mol …......(ii) On subtracting Eq. (i) from Eq (ii), we get CH2+
3
2
O2───▸CO2+H2O;ΔH=−158kcal∕mol ∴ Enthalpy of combustion of one CH2 unit =−158kcal∕mol ΔHcomb (C10H22)=ΔHcomb(CH4)+9×ΔHcomb(CH2) =−210+(9×−158) =−1632kcal