Question

Explain why the calculated value for the (1) enthalpy of combustion for propane using bond energies (bond breaking and bond formation)might not be in close agreement to the values calculated using (2) Hess Law and the values calculated using the (3) summation of the change in enthalpies of products minus the summation the change of enthaplpies of reactions?


(1) Bond Energies Value:

(2) Hess Law Value:

(3) Summation of Enthalpies Value:

Explanation: