MadSci Network: Chemistry |
How much energy can you obtain by detonating 1 Kg of TNT?
The NIST Chemistry WebBook gives several references for the heat of combustion ("DHc") of 2,4,6-trinitrotoluene (TNT). The balanced equation for this reaction is C7H5N3O6 + 21/4 O2 ® 7 CO2 + 5/2 H2O + 3/2 N2 The heat of combustion of TNT is about 3400 kJ/mol (810 kcal/mol), or about 15 kJ (just under 4 kcal) per gram. This value is a good indicator of the energy available from the detonation of TNT.TNT requires a substantial amount of oxygen (42% oxygen by weight, or about ¾ gram oxygen per gram of TNT) for complete combustion. It is commonly mixed with other explosives in various proportions depending on the application. Presumably TNT is mixed with compounds which have extra oxygen, for example ammonium nitrate or nitroglycerine. The energy released by detonation of such mixtures will vary with the exact composition. The Ordnance Shop is a good basic source for information on explosives with military uses. More detailed chemical information can be found at the TNT link given above. Incidentally, there is another, brief answer on our site.
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Jason Goodman adds the following comments:
You answered 15 MJ/kg, based on complete combustion of TNT. However, the questioner asked about energy of *detonation*, which I expect is substantially less, since atmospheric oxygen is unavailable to complete the combustion after the expansion of hot gases following detonation.
In fact, computations of nuclear weapons yields, asteroid strikes, and the
like (megatons, kilotons, etc.) use a value of about 4 MJ/kg.
- from the sci.space FAQ (http://www.ksc.nasa.gov/facts/faq04.html)
- from John Christie's answer in the previous Madsci question
you mentioned:
All of these results are consistent with 4.3 MJ/kg, with 10%
uncertainty.
Admin Note: Please note, the value Dr. Berger quotes above
is based on the heat of combustion, not the heat of detonation and
there is a large difference between them. -- RJS.
Try the links in the MadSci Library for more information on Chemistry.
You want: kilojoules
* 4612.0705
/ 0.00021682236
1 megaton (MT) TNT = about 4.2e15 J or the energy equivalent of
about .05 kg (50 g) of matter. Ref: J.R Williams, "The
Energy Level of Things", Air Force Special Weapons Center (ARDC),
Kirtland Air Force Base, New Mexico, 1963.
I have lifted a value of 4 * 10^9 joule [for detonation
of 1 ton TNT]
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