[liliesx3]

Using average bond enthalpy values estimate the heat (kJ/mol) given off in the following gas phase reaction.

2CH2=CHCH3 + 2NH3 + 3O2 --> 2CH2=CHCN + 6H2O

First I calculated the:

Number of Bonds/type of bonds being formed:
2     C=N
12    H-O

Number of Bonds/ type of bonds being broken:
6    C-H
6    N-H
3    O=O

Avg Bond enthalpies (in kJ/mol)

C=N = 866
H-O = 467
C-H = 416
N-H = 391
O=O = 498

What I did was add the enthalpies of the bonds form and add the enthalpies broken and subtract.

So this is what i did:

Bonds formed = 2x866 + 12x467 = 7336
Bonds broken = 6x416 + 6x391 + 3x498 = 6336

subtracted = 1000kJ/mol

But when plugging it in as my answer for my online hw, i got an incorrect answer. can anyone guide to the direction that was overlooked?

[UG]

That should be bonds broken - bonds formed. You'll just have to add a negative sign

[liliesx3]

thank you