8.77 Bond Enthalpy (Benzene)

[Kathleen Vidanes 1E]

On homework question 8.77, why is it that the 6 C--H bonds within benzene are not added to the 3 C double bonds and the 3 C single bonds?

[Vivian Nguyen]

The 6 C-H resonance stabilized bonds are not added because the question asks for the difference in the stability/molar energy depending on the types of bonds are considered. As a result the 6 C-H resonance bonds are one calculation while the 3 C double bonds and 3 C single bonds are the calculation in the comparison.

[Ryan Fang 1D]

While you can add the 6 C-H bonds into both calculations, because you are finding the difference between your two calculations, adding the C-H bonds to both won't make a difference.