2NH3(g) + Cl2(g)---> N2H4(g) + 2HCl(g)?

How do I find bond dissociations to calculate transfer of heat degrees in kilojoules for this equation? I'm missing something. In a chart I have N-H bond dissociations are 390. But, I don't know how they arrived at that answer. I also have a detailed chart for periodic table that shows covalent radius 14 (superscript), that shows C as .77. Am I in the right area? I am confused with this part in my chemistry, can anyone help?

Answer:
You want a table of bond dissociation energies. It'll probably be in the chapter but it could be at the end of the book.

You need to look up the following:
NH bond (390 seems reasonable in kJ/mol)
Cl-Cl
H-Cl
N-N (make sure it is a single bond - it will be a small number because those bonds are weak)

On the left you have 6 NH bonds and 1 Cl-Cl bond. On the right you have 4 NH bonds, 1 NN single bond, and 2 H-Cl bonds.

The enthalpy of the reaction is equal to the bonds you break (positive -- putting energy in) MINUS the bonds you form (negative because that takes energy out).
CRC Handbook of Chemistry and Physics

You can find it in most libraries.

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