A particular natural gas consists, in mole percents, of 83.0% CH4 (methane), 11.2% C2H6 (ethane), and 5.80% C3H8 (propane). A 385-L sample of this gas, measured at 21C and 739 mmHg, is burned in an excess of oxygen gas.
CH4=-890.3
C2H6=-1559.7
C3H8=-2219.1
kJ/mol