Bond Energies

Bond energies require knowledge of molecular structure
O2: O=O     N2: - has a triple bond (still need to figure a few symbols out)

Formation reactions: produce one mole of product from elements in their standard state
-remember HOFBrINCl & the making one mole of product
Na(s) + 1/2 H2(g) + C(s) + 3/2 O2(g) --> NaHCO3(s)

Last but not least when calculating a reaction's enthalpy change (H):
Bonds broken - bonds formed
              (reactants)                             (products)
Yes, it is the reverse of the other calculations.

Please note that H (enthalpy change) is not the same as Hx (molar enthalpy change)
One more thing before wrapping up. Consider the generic reaction:

2A  +  B  -->  A2B  H = -300kJ

molar enthalpy of A: HA = -150kJ/mol 
molar enthalpy of B: HB = -300kJ/mol
[That is all for today. Question: What is the name of the molecule bunny-O-bunny? Answer: An ether bunny  Question: What is a cation afraid of? Answer: A dogion.]