[jsmith613]

http://answers.yahoo.com/question/index?qid=20100214105517AAJIU89&r=w

look at this question
they said endothermic:
BUT
C + CO2 --> 2CO

the bond entalphy for CO is 200
the bond enthalpy for CO2 is 177

200 * 2 = 400
177 * 2 = 354

+354 - 400
= -46
should the reaction not be -46 kJ (exothermic)

following the method above, why is the reaction NOT exothermic

[sjb]

Several things here, some may be less related than others.

I'm not sure that the figure for CO is right (does not seem to take into account that the C#O is a triple bond in carbon monoxide).

Unless you're talking about an isolated carbon atom, you also need to take into account the C-C bond strength I think

Yahoo may be wrong

[AWK]

Use Standard enthalpy change of formation from wikipedia instead. Note, entalpy of bond formation usually are a very crude aproximation.

[jsmith613]

Unless you're talking about an isolated carbon atom, you also need to take into account the C-C bond strength I think

since when was there a C-C bond?

[jsmith613]

Use Standard enthalpy change of formation from wikipedia instead. Note, entalpy of bond formation usually are a very crude aproximation.

Carbon monoxide has a triple bond, therefore it must required more energy than a C=O bond

although wiki disagrees with this - i don't know why. please explain