Chemical Forums
Specialty Chemistry Forums => Other Sciences Question Forum => Topic started by: crack3rjack on April 21, 2004, 01:36:52 PM
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If you introduce a small to fair amount of CO2 to a fire, mixed with O2, how much will it prevent the fire from burning? Also, is it the O2 that a fire needs to burn? or is it just air in general?
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I don't know a terrible amount of the actual chemistry of combustion, but you DO need the O2. C02 doesn't help a fire, its a byproduct of fire.
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Yes here's the composition of air:
78 percent nitrogen, 21 percent oxygen, 0.9 percent argon, 0.03 percent carbon dioxide
So, most of the air is nitrogen, which does not participate in combustion. So generally, the equation for combustion is:
Organic material (C,H,O atoms) or fossil fuels (C,H atoms) + O2 => H2O + CO2
And yes, combustion produces water, which is how mufflers can develop rust and why they're seen to drip out water on cold days.
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Not all combustions involves oxygen. Lithium, for example, will burn in an atmosphere of pure nitrogen. Magnesium will burn in the presence of carbon dioxide. Just about everything will burn in the presence of fluorine. So whether or not something burns really depends on the chemical composition of the substance, and whether or not there is an oxidizer present. (Because it's the oxygen atoms that allow things to burn. It's the presence of an oxidizer which is able to take electrons, so to speak, away from a fuel.)
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When I think oxidizer, I automatically think oxygen. But an oxidizer can be anything that takes away electrons, right? I also remember hearing that florine is REALLY dangerous stuff, so if you used that as an oxidizer, wouldn't that make a nice lethal byproduct?
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Right, there are many reactions, that are spontaneous and involve burning, but combustion of hydrocarbons are their own catagory of reactions. I wonder if combustion reactions also encompass those type of reactions too.
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I remember reading somewhere that combustion, strictly speaking, involves the consumption of O2. Although people use the term combustion loosely
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agreed. I've never read anything to the contrary. combustion is not combustion without O2
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As for fluorine, it isn't really the byproduct in most cases you need worry about, F2 is a plain VICIOUS gas, and is a great problem to handle it, try to vent some from a monel/passivated nickel metal pressurised canister, through a standard hose, and that hose bursts right into flames, spewing lethal fluorine gas everywhere.
If you were to theoretically make sodium fluoride directly, I would be FAR more happy around the NaF, than around fluorine gas, I tried making elemental fluorine a couple of years ago on a nano scale, didn't succeed, as my chemistry knownledge was not quite up to the level it is now, but put it this way, it involved a gas mask with acid gas filter, and FULL body protection, with elbow length gloves, full facial protective hood and eye protection, and a somewhat nervour chemist working in a very well ventilated garage with the door WIDE open ;D
Be careful with fluorine, it bites, and when it does, it bites like a bone-dissolving pit bull ;D
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F2 is a plain VICIOUS gas, and is a great problem to handle it, try to vent some from a monel/passivated nickel metal pressurised canister, through a standard hose, and that hose bursts right into flames, spewing lethal fluorine gas everywhere.
Are you speaking from experience? :P
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obviously!
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I used the monel metal canister as an example of what it takes to store F2 safely, I have once prepared elemental F2 on a very small scale, which, as expected, set the rubber hose on fire at contact.
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Whoaaa how do I make this stuff(Flourine)?
JUST Kidding. Sounds like a dangereous gas. Isn't it one of the most reactive elements known to man?
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Whoaaa how do I make this stuff(Flourine)?
JUST Kidding. Sounds like a dangereous gas. Isn't it one of the most reactive elements known to man?
Fluorine is made by electrolysis of NaF(l)
Fluorine is the most reactive element
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Getting back to combustion,
Fluorine is the most reactive of the non-metals, and will combine with most other elements. Only a few of the noble gases do not combine with this element. It corrodes platinum, a metal that resists most other chemicals. In a stream of fluorine gas many substances burn with a bright flame, including finely-divided metals, glass, ceramics, carbon, wood, rubber and even water.
from Visual Elements (http://www.chemsoc.org/viselements/pages/data/fluorine_data.html)
GLASS?? Now THAT I've gotta see...a movie of it I mean :P...Pretty rough stuff.
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Wow. Corroding ceramics and glass. THAT"S NUTS.
How are you suppose to store the stuff?
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I think that fluorine reacts with glass forming silicon tetrafluoride (Glass is a silicate). No idea how fluorine is stored, though.
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It is enough to cover inside of the bottle with paraffin.
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Borek, are you suicidal? the F2 would definately first fluorinate the hydrocarbons, then would gradually exchange fluorine bonded to the hydrocarbons with free F2, and slowly begin to attack a non-resistant container.
That is, if the fluorine didn't just burn the grease on contact, although I don't think it would, I do know a film of hydrocarbon grease is only a temporary stopgap though to increase the life of glass ampoules.
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Borek, are you suicidal?
My mistake - parafin works not for F2 but for HF. For F2 nickel or Monel alloy should be used, as they get passivated.
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Crackerjack--
"If you introduce a small to fair amount of CO2 to a fire, mixed with O2, how much will it prevent the fire from burning?"
Since the equilibrium of most combustion reactions lies incredibly far towards the formation of products, the accumulation of products (CO2 + H2O will not drive the reaction backwards or even approach equilibrium. Therefore, you can be sure that as long as the atmosphere contains a decent percentage of O2 like say 21% it doesn't matter whether the other gas is N2, Argon, or CO2
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agreed. I've never read anything to the contrary. combustion is not combustion without O2
I can second that..