Chemistry CW - Calculating the theoretical Energy transfer of 6 alcohols per mole of fuel.?

Question

For methanol, ethanol, propanol. butanol, pentanol and hexanol i need to find the theoretical energy transfer if they were burned in air (oxygen).

This requires balancing the equations which i have already done but when it comes to the actual calculations, my results have no pattern and aren't all negative numbers (as they should be as they are exothermic.) I know they are wrong but i can't see where I am making the mistakes. If someone could explain, do one example for me, i would be so greatful, here's what you need to know:

The equation: Alcohol + Oxygen ---> Carbon dioxide + Water
Bond values (Kj/mol)
H-C - 413
C-C - 347
O-C - 336
O=O - 498
C=O - 805
O-H - 464

eg. balanced: 2CH3OH + 3O2 ---> 2CO2 + 4H20
for all equations:
O2 = double bond
CO2 = C=0 double bond x2
all other compounds/elements contain single bonds

Thanks so much to anyone who can help, i have been struggling with this for so long now.

other balanced equations if needed:

Ethanol: C2H5OH + 3O2 ---> 2CO2 + 3H20

Propanol: 2C3H7OH + 9O2 ---> 6CO2 + 8H2O

Butanol: C4H9OH + 6O2 ---> 4CO2 + 5 H2O

Pentanol: 2C5H11OH + 15O2 ---> 10CO2 +12 H2O

Hexanol: C6H13OH + 9O2 ---> 6CO2 + 7H2O

Answer 1

In your example, bonds broken =
6 x C-H
2 x C-O
2 x O-H
3 x O=O

Bonds formed =
4 x C=O
8 x O-H

It should work! Remember to compare like with like, so you would halve this value because you started with 2 moles of methanol.