[positiveion]

[Grundalizer]

The top question confuses me also, I do not get why they left out the C-C bond on the right.  Sometimes if the same bond that is made on the right is broken on the left, people cancel out the bonds and don't bother writing them...although that doesn't seem to be the case here.

As for the bottom question.  Remember that the enthalpy of reaction is products minus reactants.

So.  Our product is CH₄ and our reactants are C + 2H₂ (notice the 2 stoichiometric coefficient)

So now try this.

1. Add together 4 x (C-H bond enthalpy) and subtract from it the enthalpies of C and 2 H-H bond enthalpies and you should come to the answer.

[positiveion]

thank you very much! that was extremely helpful.

but um i have another question i was wondering whehter you could help me out with it?