This is something I've been wondering for a while - just what exactly is the most energetic known chemical reaction? To be more specific, the
most energetic chemical reaction involving [reasonably] stable reagents (to disqualify reactions like U(92+) +92 e- -> U, which, while obviously
hideously energetic and technically a chemical reaction, you're obviously never going to have U(92+) ions in normal conditions).Mr. Wizard - 20-3-2004 at 07:04
What do you mean by 'most energetic'? Are you talking about speed with the energy being released in the shortestest amount of time, are you
talking about the the most energy per mole formed disregarding weight? I would guess diatomic hydrogen forming from atomic hydrogen, although not
stabil, would be a candidate. Acetylene and ozone would be energetic, but the molecular weight of the components starts to get in the way. Rocket
technology takes the weight of the components into consideration with the concept of exhaust velocities, with higher exhaust velocities being better.
I think hydrogen and fluorine or hydrogen and ozone would be near the top in those categories.
[Edited on 20-3-2004 by Mr. Wizard]Geomancer - 20-3-2004 at 08:25
Assuming your talking energy/mass, F+Li should make the short list. Although (to my knowledge) none have been prepared in macrosopic amounts, exotic
nitrogen allotropes could blow everything else out of the water. There was also some speculation that helium can form a solid excimer that could be
stabilized with lasers or something (He IV-A).Pyrovus - 21-3-2004 at 00:06
Yeah, I did mean energy/mass, so this probably limits things to the first 2 groups. Pity helium compunds haven't been discovered yet . . .
I'm not sure if this has ever been prepared in large quantities, but O4 was found to exist a couple of years ago - perhaps this could be used
instead of ozone to make reactions even more energetic?Mr. Wizard - 21-3-2004 at 06:17
I found a reference to monoatomic hydrogen as a fuel, use this thread to do your own search, as I can't verify any of it. It sure is energetic!
Robert I. Eachus (eachus@spectre.mitre.org)
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In article <3hb9vk$cl1@planchet.rutgers.edu> dms@atlantis.utmb.edu (David M. Stoner) writes:
> Unless I'm missing something, the energy density would
> have to be greater than that in the chemical bonds in rocket fuel
> by a factor equal to the fuel-to-payload ratio of the rocket
> lifting the payload into orbit. Are chemical energy densities that
> large possible at all?
The first single-stage-to-orbit launch was an Atlas rocket in 1958. Higher energy-density fuels give you a better specific impulse (Isp) which
increases the mass-ratio (mass in orbit/mass at launch) that can be attained.
AFAIK, the best possible chemical fuel is monoatomic hydrogen. (Hydrogen atoms as opposed to H2 molecules.) Yes, it is stable enough at low
temperatures, and although I wouldn't want to fly in a single-H fueled spacecraft, it would be very well suited to this role. (Single-H has about
12 times the Isp of the Space Shuttle main engines, which are pretty close to the limit for ordinary fuels. I think they achieve an Isp over 400
seconds, and the best you can get with hydrogen and ozone is about 409. Atomic rockets reached Isps of 800 in tests, and gaseous core reactors were
predicted to reach Isps of 2000, single-H, as I remember is in the 5000 range.)
My chem text....
Hermes_Trismegistus - 21-3-2004 at 21:14
seems to think that the thermite reaction is one of/the most powerful commonly run reaction, all depending on how you define "common"Geomancer - 22-3-2004 at 19:26
Depending on your definition of common, indeed. Thermite is apparently spectacular (I haven't tried it, but everyone who has seems to be
impressed), and so people naturally assume it's terribly energetic. In thermite, though, iron oxide serves as an oxidizer. Burning iron is quite
energetic, and this is energy that you will lose comparing thermite to simply burning Al in oxygen. Moreover, the iron doesn't even have the
courtesy to have low mass. It's just dead weight. And, there are better oxidizers than oxygen. Get yourself some Flourine hexaphlogistonate. The
reaction 3F<sub>2</sub>Pg<sub>6</sub>+2Al should be spectacular.BromicAcid - 22-3-2004 at 19:31
Burning zirconium in a pure oxygen atmosphere can reach temperatures of 4930 K.Nick F - 23-3-2004 at 04:46
Geomancer, don't make up elements!!
Does tetrafluorohydrazine exist..?Mr. Wizard - 23-3-2004 at 07:48
Nitrous oxide isn't even a very good oxidiser. Anyone know what a normal oxy-acetylene torch can reach?
I still think nitrogen fluorides would be good oxidisers, in conjunction with acetylene or cyanogen or something. Not the most energetic, but I bet
you'd get one hell of a flame...
Oxy-acetylene
chloric1 - 23-3-2004 at 11:08
I have heard that 6000 F for oxyacetylene. oxy propane is 5400 F and it only melts steel with difficulty but oxyacetylene is much better. (Keep in
mind the losses , so your flame always needs to be much hotter than the melting point).Mr. Wizard - 23-3-2004 at 19:12
I think Acetylene and Oxygen are hotter and more energetic than Acetylene and Nitrous Oxide. I didn't read enough before I posted. I have seen
information of temperatures in excess of 3150 C with C2H2 + O2.
(1.8 x 3150 =5670) + 32 =6002 F
!smokin'!4s2 - 12-4-2004 at 05:02
actualy... Oxy/Acetylene doesnt get quite that hot in a typical flame. Using a blossum or rosebud or just tweaking your settings can get you above
that.
Also the rxn is not just C2H2 +O2. If this was the only rxn, it would suck for welding becuase oxygen would readily form in the weldment. Instead
there is a 2-3 part rxn that includes air, and generates about 200,000 cal of heat.
(this is only for a neutral flame, other types of flames produce different rxns but vary only slightly with Oxidizing flame and Reducing / Carburizing
flames)
A) C2H2+O2 -> 2CO +H2
B) CO+ (1/2)O2 -> CO2
C) H2+(1/2)O2-> H2O
I wasnt sure so I looked it up and found that there also N in the rxn, but it doesnt react. (unless this AWS book was in err.)
there are hotter burning gasses like Hydrogen + Fluorine. but I beleive the products are extreamly toxic/deadly.
All in all though, if you figure your highest melting point of most metals and metal alloys is well below its max heat of 3,200C (it just might take
you awhile to head up some tungstun...AndersHoveland - 26-5-2012 at 12:32
The most energetic reaction, on a weight basis, is between beryllium and oxygen. This releases slightly more energy than even the reaction between
lithium and fluorine. Actually the most energetic reaction would react beryllium with ozone, but ozone is typically unstable, and much more difficult
to work with.
Beryllium and Oxygen together release 24.36 kJ/g. Lithium and Fluorine release 23.75 kJ/g. Using ozone instead to burn Be would yield 26.26 kJ.
Another possibility would be to burn OF2 with a Li-Be alloy. Oxygen difluoride will yield 23.8 kJ/mol extra energy than a comparable mixture of O2 and
F2. There are 54g/mol for OF2, thus it is calculated that the use of OF2, rather than O2 and F2, reacting with Li2-Be should provide an extra 0.44
kJ/g.
"A New Determination of the Heat of Formation of Oxygen Difluoride" by WARREN R. BISBEE, Rocketdyne Division, North American Aviation
The heat of formation of OF2, with this newly determined value, is 16.994 kJ/mol (0.3147 kJ/g); this calculation does not agree with my earlier one.
Wikipedia claims a 24.5 kJ/mol heat of formation, which gives a value of 0.454 kJ/g. Thus, three different values have been calculated for the
additional energy OF2 would contribute.
Lithium is fairly expensive (US$95/kg). Beryllium is much more so ($745/kg), explaining why these metals are not commonly used in rocket propellents.
The highest specific impulse for a chemical propellant ever tested in a rocket engine was lithium, fluorine, and hydrogen (a tripropellant),
which gave a value of 542 seconds (5320 m/s). In normal rockets that burn H2 with O2, extra liquid hydrogen is used beyond the stoichiometric
quantity. The heat released from formation of water molecules causes the excess liquid hydrogen to boil, and this is what provides the thrust. Liquid
oxygen is much heavier than liquid hydrogen, and this is why using extra hydrogen has a higher specific impulse than burning all the hydrogen.phlogiston - 26-5-2012 at 16:38
Quote:
No Phlogiston?
Seriously. I read where Acetylene and Nitrous Oxide are used in a flame doing atomic absorbtion testing and it reaches 2900 C. Very warm.
Talking to me?
In terms of flame temperature, dicyanoacetylene rules.
5260K (4990 C, 9010F) if burned in oxygen...
@Pyruvus, reactions like U(92+) +92 e- -> U 'cost' a lot of energy. I think most people here are assuming you mean reactions that 'yield' energy.
Please define 'most energetic'.
