13. A mixture of air and a hydrocarbon fuel whose average composition is indi- cated by CH19 undergoes complete combustion. Twice as much air is present as needed to burn all the fuel. How high is the final temperature? The heats of formation are given in the table below. Assume that air is 79% nitrogen and 21% oxygen by volume. The reactants have a temperature of 25C before combustion. The adiabatic flame temperature may be found either by using average values of the specific heats for each constituent. Constituent CH19 CO (g) O (g) N (g) HO (g) QkJ/kmol K @ 298 K , kJ/kmol. K 9,358 -393,522 0 0 -241,827 51.9 34.0 31.6 40.6