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March 24th 04, 10:53 AM
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(John Michael Williams) wrote in message . com...
(Bill Sloman) wrote in message . com... (John Michael Williams) wrote in message . com... ... I share this skepticism. Burning TNT probably would produce 10x more free energy than detonating it. Trinitrotoluene is C7H5N3O6 and would burn to 7 CO2 molecules, 2.5 H2O molecules and 1.5 N2 molecules - for which you'd need 10.5 extra oxygen atoms, over and above the six oxygen atoms available in the original TNT molecule. Being simple-minded about it, 16.5/6 is 2.75, not ten, and that exaggerates the advantage, because burning carbon to carbon monoxide release quite a lot more energy than burning carbon monoxide to carbon dioxide, which is where you use up seven of your extra 10.5 oxygen atoms. Right, letting the N_3O_6 drop out as nitrogen dioxide, 7*CO_2 + 2.5*H_2O is just 16.5. However, detonation might not even produce the nitrogen dioxide, and it might lose energy by producing NO instead of dioxide. So I'm not sure where the 6 comes from. Detonating or burning TNT won't produce any significant amount of nitrogen dioxide - the oxygen originally bonded to the nitrogen will end up bonded to the hydrogen (as water) and the carbon (as carbon monoxide). That is what the nitrate groups are there for. Also, the energy from C+O_2 would be much lower than that from the H_2+O, per O, I think, but I'm not sure how well defined the combustion process is, that is being assumed. It is pretty well defined. The hydrogen-oxygen bond is stronger than the carbon oxygen bond, so all the hydrogen is going to end up as water, and the rest of the oxygen will be taken up as carbon dioxide. The energy released by these reactions can be worked out pretty exactly - the National Bureau of Standards publishes table of "enthalpies" for loads of chemical compounds. You have to fine-tune the published data to account for the temperature and physical states of the reactants before and after the reaction, but this is strictly detail work. The procedures involved in making the calculations were covered in the thermodynamics course I did in second year chemistry back in 1961. As far as I know, all chemistry and physics graduates have to do such a course. I think, if detonation in air also entailed complete combustion, then detonation would produce the same energy as would direct combustion. Detonation can't entail complete combustion - at least not for TNT, where the three nitro-groups don't provide enough oxygen - in the ratio 6 : 16.5 - for complete combustion, and atmospheric oxygen can't diffuse into the fire-ball anything like fast enough to make up the deficit. As Don Klipstein has pointed out, nitroglycerin and PETN (penta erithytol nitrate IIRR) do contain enough nitro-groups to allow more or less complete combustion during detonation. You mentioned something earlier about atomic hydrogen: I am not sure about this, because combination to H_2 would just be creation of one covalent bond. Can you explain further? It is "just" the creation of one covalent bond, from a situation where there was no covalent bond. Most chemical reactions involve exchanging one covalent bond for another - stronger - covalent bond. The noble gases - helium, neon, argon, xenon, radon - are the only elements that don't form strong covalent bonds. You've got to heat most elements to astronomic temperatures before you see appreciable populations of single atoms. The exact amounts of energy involved are all available in the open literature - that is where I found them, some thirty years ago, and I'm sure that they are still available now. ------- Bill Sloman, Nijmegen |
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