C8h18(l)+252o2(g)? 8co2(g)+9h2o(g)calculate ? hrxn for the combustion of octane (c8h18), a component of gasoline, by using average bond energies. calculate ? hrxn for the combustion of octane by using enthalpies of formation from appendix iib in the textbook. the standart enthalpy of formation of c8h18 is -250 kj/mol. what is the percent difference between the two results? which result would you expect to be more accurate? a) the value calculated from the heats of formationb) the value calculated from the average bond energies