Exact Thermodynamics of Propane Combustion As a logical extension to the time-honored exercise of computing adiabatic flame temperatures in physical chemistry, we have used the heterogeneous equilibria computer program of Gordon and McBridel to generate the composition of the products of combustion of 1 mole of propane, 5 moles of Oz,and 20 moles of N2.The progam was operated in the H , P mode with the initial and final enthalpies equal to that of the reactants a t 25°C and the total pressure fixed a t 1 atm. The final temperature turns out to he a dependent variahle with the value of 2219°K. Some fifty reaction products are considered in the CHON atomic scheme, including solid carbon, with the ten most abundant listed in the Table. Ten Most Abundant Combustion Products of Propane Gaseous
S~eeies
Male Fraction
Gaseous
S~acies
Mole Fraction
Gaseous
Scecies
Mole Fraction
G-89~ S~seies
Mole Fraction
Equilibrium constants for a number of reactions can he computed directly from these mole fractions, for instance the dissociation of H2 and 0 2 , the oxidation of CO, and the reactions of formation of NO and HzO. We have found that the computation of exp(-AG0/RT) a t the final flame temperature, from data found in standard texts, makes the very powerful taols of chemical thermodynamics a hit less abstract when these exponentials turn out to very closely match the corresponding partial pressure quotients. The computer has done all of the hard work of solving the many nonlinear simultaneous equations for us. 'Gordon, S., and McBride, B. J., NASA SP-273, "Computer Program for Calculation of Complex Chemical Equilibrium Compositions," National Technical Information Service. Springfield, Virginia. University oCUrnvcr Denver, Coloradu All210
D. H. Yean J. R. Riter, Jr.
Volume 51, Number 8 . August 1974
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