[THISMOMENTISFATE]

Bond energies, check my problem?
im trying to solve this problem, can someone check where i made the mistake?

Calculate the Hrxn using Bond energies (BE) for the following reaction.
N2 BE=945 kJ H2 BE=432 kJ N-H BE=391 kJ

N2 + 3H2 ---> 2NH3


Solution:

945 + 3(432) --> 2(391 x 3)
2241---> -2345
= -105

but the problem says the right answer is -2346

i have a test tomorrow,, can someone help?

[Wald_ron]

 :delta:H rxn = H products - H reactants

[THISMOMENTISFATE]

i tried that i stilll dont get the right answer'

[Borek]

IMHO answer you have listed is incorrect. 2346 = 2*3*391, seems like 2346 is total bond energy in products, not Hrxn.

[THISMOMENTISFATE]

ive tried to solve it two ways does anyone know which one is right?


[945 + 3 (432) ] - [2(391) + 432]
2241-1214
1027


or:

[945 + 3 (432) ] - [6(391) ]
2241-2346
-105

which one is right, does anyone know?

[Astatine]

I believe that -105kJ/mol is indeed the correct answer.

[THISMOMENTISFATE]

Thanks, for the help everyone!