Bond Enthalpies

[Giselle Littleton 1F]

I notice that in some problems from the homework, specific bonds within molecules aren't included when calculating the bond enthalpies. Why is that and how can I watch out for those that I should not include?

[sarahsalama2E]

I'm not sure if this is exactly what you are referring to but molecules in their most stable state, aka H2, 02 do not have bond enthalpies because they are in their most stable state, because it takes no energy to form a naturally-occuring compound that wants to be formed.

[Shrayes Raman]

I may be misunderstanding your question however you do not need to include bond enthalpies for bonds that are not broken in a reaction, ie 3C2H2 -> C6H6 do not need H - C bond enthalpies because they are not broken

[Maika Ngoie 1B]

Normally bond enthalpies should be stated, unless it is the most stable form of the naturally occurring element, in which case it does not have a bond enthalpy.

[Micah3J]

If on a test we were asked to use Hess's law, we would be given a table that shows the bond enthalpies right? If anything I just need to remember which ones are 0.