Stoichiometry of ΔHrxn

• For example, the balanced equation and ΔHrxn for the combustion of propane (the fuel used in LP gas) is as follows:

C3H8(g) + 5 O2(g)  3 CO2(g) + 4 H2O(g) ΔHrxn = −2044 kJ

• When 1 mole of C3H8 reacts with 5 moles of O2 to form 3 moles of CO2 and 4 moles of H2O, 2044 kJ of heat are emitted.
• These ratios can be used to construct conversion factors between amounts of reactants or products and the quantity of heat exchanged.