[hilsenna]

Hi,

I solved the "a" part of the problem by 22,4 L* 2 moles of oxygen. On the other hand, I could not solve the part "b", I do not understand how we are going to use sublimation of graphite and bonding energy of hydrogen here? Dont we need to know the bonding energy between oxygen, and C-O, and O-H?

By the way answer is 75 kj/mol

[AWK]

http://www.docbrown.info/page07/delta1Hb.htm

[Enthalpy]

You're probably supposed to assume that sublimation breaks the bonds from solid graphite.

It's an old trap from reaction heats: chemical formulas for solids may be written  as "C" or "Fe" but they are full of bonds.

However, gaseous graphite contains varied polyatomic molecules like C₂, C₃, C₄. The composition isn't even known exactly. In that, I disagree strongly with the question. What is needed is the atomisation energy.

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I don't like neither a heat of formation estimated from bond energies. You add and subtract quantities like 700kJ/mol to get 75kJ/mol. This can't be accurate.

Deducing a heat for formation from the heat of combustion is less bad. A heat of hydrogenolysis would be better but seems impractical in many cases, and for methane it's excluded by logic.

[AWK]

The numerical data in this problem are matched with the atomization energy.
http://ursula.chem.yale.edu/~chem220/chem220js/STUDYAIDS/thermo/atomization.html#:~:text=The%20calculated%20heat%20of%20atomization,atoms%20is%20379%20kcal%2Fmol.