[curiouscat]

Another thread (*) got me thinking: What's the most exothermic reaction you know of? To quantify exothermic in a sane manner let's base it on kilograms of reactants. i.e. If you mix a kg of reactants (any number) what's the most kJ of energy any one reaction gets you?

I'm starting with H2 + 0.5 O2  H2O ~16 MJ/kg by my calculation.

So burning a kg of this H2 / O2 cocktail can boil away ~7 kg of water. Not bad.

But can you do better?   


PS. Let's exclude nuclear reactions.

* http://www.chemicalforums.com/index.php?topic=74941.0

[Zensation]

Not a specific reaction here... but surely various concoctions of Thermate would make it onto the list. Thermite burns very hot as it is, Thermate, can get up to 4-5x hotter, easily. If you're familiar with it.... you're talking about less than a gram of this can melt through steel.... Lets see your H2O beat that!

(by the way if anyone has any specific figures for any particular Thermite/Thermate blend, I would love to hear them)

[Borek]

TNT 4.2 MJ/kg

(I am not listing it as a contender, as it is way too low, just to not let others waste the time checking).

[curiouscat]

Not a specific reaction here... but surely various concoctions of Thermate would make it onto the list. Thermite burns very hot as it is, Thermate, can get up to 4-5x hotter, easily. If you're familiar with it.... you're talking about less than a gram of this can melt through steel.... Lets see your H2O beat that!

(by the way if anyone has any specific figures for any particular Thermite/Thermate blend, I would love to hear them)

Actually the numbers don't seem as big. I'm getting ~4 MJ/kg for the thermite mix

Fe2O 3 (s)  +  2 Al (s)    Al2O 3 (s)  +  2 Fe (s)

Exotherm is -849 kJ/mol of iron(III) oxide says an online source.

So on a per kg basis only 1/4th as much as exothermic as a H2/O2 mix. Way to catch up Thermite!

[Borek]

http://en.wikipedia.org/wiki/Energy_density_Extended_Reference_Table

Be/O₂ seems to be a winner.

[curiouscat]

TNT 4.2 MJ/kg

(I am not listing it as a contender, as it is way too low, just to not let others waste the time checking).

Good call. You kinda get to the crux of my post's intention. What reactions one might intuitively (naively?) think of as winners on exothermicity are often not.

PS. TNT, thermite etc. will show up far stronger contenders on a per volume basis, for any reasonable H2 storage pressure I suspect.

[curiouscat]

http://en.wikipedia.org/wiki/Energy_density_Extended_Reference_Table

Be/O₂ seems to be a winner.

Yep. I think that settles it. 24 MJ/kg. 50% higher than H2+O2. I was suspecting something of this sort.

H2  + O2 is surprisingly high, for all it's non exotic-ity.

Also, water is a surprisingly good coolent. I'd never have imagined that the most energetic (non nuclear) cocktail in the world has only enough energy per kg to evaporate barely 10 kg of water.