Chemical Forums
Specialty Chemistry Forums => Other Sciences Question Forum => Topic started by: tortoise on May 02, 2005, 03:02:37 AM
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hey brothers :) :)Help me solve this problem: Why doesn't water burn???
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What would the product be?
H2O + O2 ---> ???
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nothing. but... I think it's not an answer :-\
I explain that the burn needs oxigen. In the water the a little oxigen (it's only enough for the fish to breath :)). So the burn can't tace place in the water. But I don't know whether it's right or wrong ???
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That would be the right answer but the wrong reasoning.
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so, please help me :)
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For something to 'burn', you need a fuel and an oxidizer. In most cases, the oxidizer is oxygen but that doesn't always have to be the case. In explosive compositions, the fuel and oxidizer are either contained in the same compound, or in a mixture of different compounds. The other requirement for something to burn is that when the fuel and oxidizer combine, they have to form a product, or products, which are more energetically stable than the starting compound(s). Graphite will burn because CO2 is more energetically stable than Graphite and Oxygen are on their own. Helium won't burn because any compound it could possibly form would be far less stable than any mixture of Helium and an oxidizer. Water doesn't 'burn' in the classic sense because water and free oxygen is far more stable than any compound those two could create together. However, that doesn't mean that water can't burn.
Add some fluorine gas to water and you will see water burn. This is because the product formed when fluorine and water react is far more energertically stable than pure water and pure fluorine alone. So in order for things to 'burn', you need three things;
1) An oxidizer.
2) A fuel.
3) Product(s) which is/are more energetically stable than the reactant(s).
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sorry, but i can't understang this sentence (maybe my English is quite bad :-\): "Graphite will burn because CO2 is more energetically stable than Graphite and Oxygen are on their own"
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That means that the CO2 compound (Carbon dioxide) is more stable than a mixture of Oxygen and Carbon (Graphite) are.
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but in the reaction of water and F2, F2 or water burns?
By the way, please delete the topic "Does water burn?"
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"burning" is a violent reaction between a substance and oxygen (either in elemental form, O2, or taken from some other compound, such as saltpeter, KNO3). Now, burning is, by definition, a red-ox reaction, and the laws of redox tell us that an atom cannot have an oxidation state that is higher than the number of electrons it can lose to obtain a full octet, or lower than the number of e- it can gain to have a full octet. Since hydrogen can only gain or lose one electron, its max oxidation state is +1, so in H2O hydrogen can no longer be oxidized. If you don't know what red-ox is (I didn't learn it in my first year of high school chemistry), then I could explain it in more depth.
Of course, many reactions *look* like a combustion reaction, such as that of flourine gas with, say, iron (or pretty much anything, including water), where the flourine acts just like oxygen would, and it looks as if the iron is burning, but in the technical sense, it isn't really, since no oxygen is involved:
2Fe (III) + 3F2 ----> FeF3 + lots of heat
Also, many reactions (such as iron rusting) would seem to be a combustion reaction; after all, the reaction is the same, whether you are burning iron or just letting it rust. (many people don't realize it, but iron burns very easily: just put a match to some steel wool. Not very exciting, but the iron's definitely burning).
Now I could be entirely wrong with my definition of "burn", but the red-ox bit is the reason for water not burning.
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The re-dox definition is correct. The definition of 'burning' or 'combustion' doesn't require the presence of oxygen, however. It only requires the presence of an oxidizer. (However, in the vast majority of the cases, most 'burning' or 'combustion' takes place with oxygen so people just say that you need oxygen to burn).
In the reaction between F2 and water, water 'burns' because it is what is being oxidized and F2 is what's being reduced. When something 'burns', it is being oxidized and is the 'fuel'. The substance being reduced is the 'oxidizer'.
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Some of my friends suppose that water is the product of combustion (?) so water can't burn !? They say they has never seen any product of combustion which can burn ::)
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Maybe water can burn. I think I may have posted about this before, but I did a search and couldn't find it. Anyhoo, these people at BlazeLabs said they made COHh and used that instead of gasoline to power a small electric generator. Will COHh burn? Its got carbon and hydrogen, and therefore I assume hydrocarbon... but whats the deal with that oxygen in there? If anyone wants the link where I got this from:
http://www.blazelabs.com/n-aquagen.asp
Maybe I posted about this on the HV forums before and forgot to mention it here... I've been very forgetful lately.
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Corvettaholic,
Ethanol has hydrogen, carbon, and oxygen in it. Throw some vodka on a fire what happens. It burns very fast depending on concentration, but from my expierence very fast. Interesting post made me think Corvettaholic. I'd imagine that your COHh would burn. It would just requires more oxygen. Ethanol is C2H5OH. I'd imagine "burning" it would look something like this:
C2H5OH + 6O2--->2CO2 + 3H2O
Correct me if I made a mistake.
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So if it DOES burn, why not make fuel on the fly while driving? The setup they used had a low voltage (50V) high current discharge through water using carbon electrodes. I guess while the water is a plasma the carbon from the electrodes somehow gets fused in with it and you get that new compound. It then bubbles to the surface and you can collect it at a little spout.
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Can Axetylen (C2H4) burn water?
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Can Axetylen (C2H4) burn water?
1. Acetylene is C2H2, not C2H4.
2. How do you imagine that acetylene can burn water? Acetylene can give a very high temperature of burning in pure oxygen, but that won't make water burn. Water can vapourise quicker, though.
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coverttolic's of burning water is effectively burning carbon. The carbon is somehow activated by water. energy is produced from the formation C=O bonds in the final combustion process. water is used to increase the reactivity of carbon, then it is regenerated in the combustion process. it isn't really burning water.
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thank you very much
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Qoute from Garneck
-"Water can vapourise quicker, though."
i think that just might be the answer(we need one dearly ;D).water has a b.p. much lower than its burning point ???
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Some of my friends suppose that water is the product of combustion (?) so water can't burn !?
In a way they are right - if you burn hydrogen in the oxygen you will get water.
They say they has never seen any product of combustion which can burn
So they haven't seen all :)
If there is not enough oxygen carbon compounds burn only halfway to carbon monoxide which can later burn to carbon dioxide.
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I think that just might be the answer(we need one dearly ;D).water has a b.p. much lower than its burning point ???
Whatever burning point is (is it ignition point?), I doubt water has one :)
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At room temperature, it burns quite violently in an atmosphere of fluorine gas. ;D
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Burning is by the common sense of the word, ignition of a combustible material in 20% O2 atmosphere
Well, water is already "burnt", it's hydrogen oxide, you can't really oxidize an oxide, unless using F2, as posted a lot of times above.
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So, does CO2 burn?
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for any reaction to occur whether it is chemical or physical,the change in the gibbs free energy has to be negative this applies to "burning of water" too or "burning of carbon di oxide" too(by burning i mean a redox reaction with free oxgen molecule where oxygen act as a ).so oxidation of carbon di oxide with oxygen is possible at some suitable temperature, but i dont think this is possible for water as in water we have hydrogen which has no electrons to donate to oxygen atoms...where as in the case of carbon we still have some electrons in the inner 1s shell which can be taken out at some suitable temperature.....therefore combustion of carbondioxide is possible
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what does re-dox mean?
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red - ox refers to reduction and oxidation
in a redox reaction, a reactant is oxidised, and another reactant is reduced. products cannot be oxidised or reduced, unless they become the reactants of a subsequent reaction.
oxidation is the increase of oxidation number, while reduction refers to the reverse.
oxidation number is the charge of an atom or ion or cation or anion whichever seems best
take a look at http://en.wikipedia.org/wiki/Redox for further info
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I recieved a question:
When we add some flourine gas to water, the reaction take places with 2 half-reactions:
F2 + H2O ----------> 2HF + O
F2 + nO -----------> OnF2
where n gainthe value from 1 to 8.
So where does the combustion process take place?
I really shock! I have never seen O2F2 or O3F2 ... I only see OF2.
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to combust something, u'll need an oxidiser and fuel. i'll think the 1st reaction sounds suitable because its redox and thus has an oxidising agent (not very sure about combustion and redox)
its possible obtain O2F2 or O3F2 in theory...
F-O-O-F and F-O-O-O-F
but there's got to be a catch.. either thermodynamic instability or something about those lines
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water can actually burn, but in the presence of the right oxidiser. at least in theory that is. of course u cant burn water in oxygen.
and if water burns... aliens that we do not wish to contemplate will live on earth instead :P
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you mean water can burn in the air?
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If we define burning as the abillity to undergoe combustion, then water can not undergoe combustion and can not be burned. Could it be oxidized? Perhaps in the presence of a good oxidizer.
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Again, that all depends on your definition of 'combustion'. As I know that steel wool can combust in an atmosphere of chlorine gas. (Here's where sematnics becomes a real pain in the ass when trying to define something). ;)
To really sum it up:
If you define 'combustion' as a chemical reacion with oxygen, then no, water cannot combust/burn.
If you define 'combusion' as a chemical reaction with a strong oxidizer, then yes, water can combust/burn.
;D
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Hi again :)
I receive an answer to the question "Does water burn?" :
Water - I would say that it does burn. In fact when cooking and the boiling water in a pot overflows, the flame turns yellow (a sooty/carbon flame) meaning that it is being burned.
Also (this is a trick answer) if water is hot and you pour it onto your hand it burns you ;)
Is it right? What do you think?
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It is so wrong it hurts my brain. If you put liquid nitrogen on your hand it burns too, it doesn't mean it is burning! The rate of heat transfer is meaningless.
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burning is a chemical process. the key word is "you". obiviously water isnt the one being burned :P
the part about spilling boiling water on a flame is familar; i've tried it before in my younger days. i think its more accurate that water is vapourised into steam, the flame becomes yellow as it has combusted something.
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The flame turns yellow because sodium ions tend to contaminate EVERYTHING and sodium ions emit a yellow color when excited in a flame.
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Weter does burn. In fact when cooking and the boiling water in a pot overflows, the flame turns yellow (a sooty/carbon flame) meaning that it is being burned.
Please check it.
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water doesn't burn because water is a product of complete combustion
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water doesn't burn because water is combustion product.
So is carbon monoxide, but CO can burn. ;)
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IF H²O could burn you probably get water
Or am i talk b*llsh*t again ???
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Now that was an interesting read! I'm going to go and convert my car to water :D
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So is carbon monoxide, but CO can burn. ;)
He said that water is the product of 'COMPLETE' Combustion - CO is not 'complete' but partial. CO2 is complete and does not burn.
So.. are we all now certain that water doesn't burn (in the conventional sense)? ;D :D ???
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He said that water is the product of 'COMPLETE' Combustion - CO is not 'complete' but partial. CO2 is complete and does not burn.
So.. are we all now certain that water doesn't burn (in the conventional sense)? ;D :D ???
Yeah, that was after he edited his original post. Hence my 'wink' face. ;D
And yes, I agree that in the conventional sense water does not burn. (Convential Sense are the important words there). ;D
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O my. This topic is really, really old.
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water doesn't burn because water is a product of complete combustion
Water can burn!!!
over a high temperatur !!!
-> H2
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Water can burn!!!
over a high temperatur !!!
-> H2
Huh? You want to elaborate on that more please.
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Well said constant thinker. Maybe we need a professional semanticist. I wonder when you translate burn into German you get a different meaning.
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If you want to see something that looks like water that burns, get some highly concentrated alcohol solution and put a match to it. It will burn, and it LOOKS like water!
Yipee! Problem solved!
:P
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One of the products of alcohol combustion is water.
Problem with that is that with some alcohols at various concentrations the color it burns it will be washed out by the ambient color. Trust me I've burnt myself doing it and it hurts.
You can use alcohol for a make shift bunsen burner. Take a glass vile and some sort of wick (napkin can work, but it tends to burn to easily).
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Corvettaholic,
Ethanol has hydrogen, carbon, and oxygen in it. Throw some vodka on a fire what happens. It burns very fast depending on concentration, but from my expierence very fast. Interesting post made me think Corvettaholic. I'd imagine that your COHh would burn. It would just requires more oxygen. Ethanol is C2H5OH. I'd imagine "burning" it would look something like this:
C2H5OH + 6O2--->2CO2 + 3H2O
Correct me if I made a mistake.
OK! ;D
C2H5OH + 3O2 ---> 2CO2 + 3H2O
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Wow will17. That was 11 months ago and I'm surprised no one caught that. I didn't eve know I had made a mistake.
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Thats a snack for sure.
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WOW- I was wondering why my scooby snack count jumped from 4 to 5! So much credit for such a little correction (I wouldn't have mentioned it if he didn't say 'Correct me if I made a mistake'!)- thanks ;)!
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Steam Explosion (http://en.wikipedia.org/wiki/Steam_explosion)
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so are you guys saying that when hydrogen and oxygen come together there is no "burning". because i've been told different.
i've been told that a hydrogen-oxygen reaction at first burns. is this then incorrect?
please explain
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North - of course hydrogen H2 and Oxygen O2 burn:
2H2 + O2 + heat > 2H2O + big bang
But what these guys are saying is that the H2O then will 'burn' no further as the reaction (2H2 + O2 > 2H2O) is fully complete. The '' marks around the word burn are there because alot of the discussion has been about what 'burn' really means.
:)
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hey brothers :) :)Help me solve this problem: Why doesn't water burn???
water is the oxide of hydrogen so essentially it is the product of a combustion reaction, thus it has already been burned.
edit: dam ^ he got to it before me.