One mole of methane is reacted with 0%-excess air. If the reactor feed gas temperature is 25^oC, the propane conversion is 100%, and the reactor is operated adiabatically, calculate the temperature of the gas mixture coming out of the reactor. Assume that the heat capacity values of the component gases are constant and equal to their values at 1000 K and that methane combustion produces only CO2 and H2O (a). Repeat the calculation using 20%-excess air (b). Explain why the results of parts (a) and (b) are different