Question

How can I figure out how much heat propane produces?

Answer 1

Std. enthalpy of combustion (Δ_cH^⦵₂₉₈) = −2220 kJ.mol⁻¹ (date taken from https://en.wikipedia.org/wiki/Heat_of_combustion)

C₃H₈(g) + 5O₂(g)   3CO₂(g) + 4H₂O(l); exothermic

The standard enthalpy of combustion (the heat of reaction) can be calculated if the bond energies are known (again, the standard data is available online or in your textbook).

Heat of reaction = Bond energy of the reactants - Bond energy of the products

(Hint: 8 C-H bonds, and 2 C-C bonds in C₃H_8; 5 O=O bonds in 5O₂; 6 C=O bonds in 3CO₂; 8 O-H bonds in 4H₂O; all you need to know is bond energies of C-H, C-C, O=O, C=O, O-H)

Here is one source: http://www.wiredchemist.com/chemistry/data/bond_energies_lengths.html