Propane (C3H8) burns according to the following balanced equation:

Question

C3H8(g)+5O2(g)→3CO2(g)+4H2O(g)
Calculate ΔH∘rxn for this reaction using standard enthalpies of formation. (The standard enthalpy of formation of gaseous propane is -103.9 kJ/mol.)

Answer 1

Now you need dH^o_f fpr H2O gas.

dHrxn = (n*dH products) - (n*dH reactants)

Answer 2

-103.9