Thermo help!

[Homoochan]

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This is a question from ExamKraker 1001 Chemistry #369.

Under standard conditions, which of the following reactions will have the greatest difference between the enthalpy and energy of reaction?

A. 2C(graphite) + O2(g) -> 2CO(g)
B. C(graphite) + O2(g) -> CO2(g)
C. C(graphite) -> C(diamond)
D. CO(g) + NO2(g) -> CO2(g) + NO(g)

can anybody help out please?

thanks!

 

[GCT]

Use the formula H= E + nRT . This formula essentially reveals that the difference in the amount of moles in the product relative to the reagents is a factor in enthalpy calculations .

 

[AZFutureDoc]

Not familiar with that equation, but it seems like it makes sense.

My only thoughts, if there are no numbers given, is to use dE=q+w. If you want the largest difference between the dE and H, thus q, you want a reaction that is going to need work done, or do lots of work. Then you'll see that C is the odd man out. Of course, you probably know that making diamond out of graphite takes a TON of PV work. If it didn't, why wouldn't we make them for cheap instead of relying on Africa and all their problems. Lol sorry, kind of a rabbit trail, but anyways.

 

[not respect]

i tihnk it's A because of the definition of Gibbs free energy, I'm guessing thats what energy means.