Pyrovus
Hazard to Others
Posts: 241
Registered: 13-10-2003
Location: Australia, now with 25% faster carrier pigeons
Member Is Offline
Mood: heretical
|
|
Most energetic chemical reaction
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
International Hazard
Posts: 1042
Registered: 30-3-2003
Member Is Offline
Mood: No Mood
|
|
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
Hazard to Others
Posts: 228
Registered: 21-12-2003
Member Is Offline
Mood: No Mood
|
|
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
Hazard to Others
Posts: 241
Registered: 13-10-2003
Location: Australia, now with 25% faster carrier pigeons
Member Is Offline
Mood: heretical
|
|
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
International Hazard
Posts: 1042
Registered: 30-3-2003
Member Is Offline
Mood: No Mood
|
|
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)
Search tool
10 Feb 1995 16:43:40 -0500
Messages sorted by: [ date ][ thread ][ subject ][ author ]
[ Next ][ Previous ] In reply to: David M. Stoner
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.)
|
|
|
Hermes_Trismegistus
National Hazard
Posts: 602
Registered: 27-11-2003
Location: Greece, Ancient
Member Is Offline
Mood: conformation:ga
|
|
My chem text....
seems to think that the thermite reaction is one of/the most powerful commonly run reaction, all depending on how you define "common"
Arguing on the internet is like running in the special olympics; even if you win: you\'re still retarded.
|
|
|
Geomancer
Hazard to Others
Posts: 228
Registered: 21-12-2003
Member Is Offline
Mood: No Mood
|
|
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
International Hazard
Posts: 3253
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline
Mood: Rock n' Roll
|
|
Burning zirconium in a pure oxygen atmosphere can reach temperatures of 4930 K.
|
|
|
Nick F
Hazard to Others
Posts: 439
Registered: 7-9-2002
Member Is Offline
Mood: No Mood
|
|
Geomancer, don't make up elements!!
Does tetrafluorohydrazine exist..?
|
|
|
Mr. Wizard
International Hazard
Posts: 1042
Registered: 30-3-2003
Member Is Offline
Mood: No Mood
|
|
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.
http://www.chemistry.nmsu.edu/Instrumentation/AAS_Gases.html
|
|
|
Nick F
Hazard to Others
Posts: 439
Registered: 7-9-2002
Member Is Offline
Mood: No Mood
|
|
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...
|
|
|
chloric1
International Hazard
Posts: 1147
Registered: 8-10-2003
Location: GroupVII of the periodic table
Member Is Offline
Mood: Stoichiometrically Balanced
|
|
Oxy-acetylene
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).
Fellow molecular manipulator
|
|
|
Mr. Wizard
International Hazard
Posts: 1042
Registered: 30-3-2003
Member Is Offline
Mood: No Mood
|
|
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
Harmless
Posts: 34
Registered: 9-4-2004
Location: Iowa US
Member Is Offline
Mood: Inspired
|
|
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.)
C2H2+O2 -> 2CO +H2 + 106,500 calories of heat.
CO+2N2 + (1/2)O2 -> CO2+ 2N2+68,000 cal.
H2+(1/2)O2+2N2-> H2O +2N2+58,000 cal.
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...
I haven\'t failed, I\'ve found 683 ways that don\'t work. -- Me.
|
|
|
AndersHoveland
Hazard to Other Members, due to repeated speculation and posting of untested highly dangerous procedures!
Posts: 1986
Registered: 2-3-2011
Member Is Offline
Mood: No Mood
|
|
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
International Hazard
Posts: 1379
Registered: 26-4-2008
Location: Neon Thorium Erbium Lanthanum Neodymium Sulphur
Member Is Offline
Mood: pyrophoric
|
|
| 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'.
-----
"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
