Is oxygen flammable?

Discussion in 'Chemistry' started by Magical Realist, May 15, 2014.

  1. Magical Realist Valued Senior Member

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    Also, why is it when we combine oxygen and hydrogen, which would SEEM to be flammable concoction, does the nonflammable compound of water result? Why ISN'T water flammable?
     
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  3. billvon Valued Senior Member

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    Alone? No, just as hydrogen isn't flammable without oxygen.
    Hydrogen and oxygen is very flammable. Water is the product of the reaction (the fire, if you will) and is not very reactive.
     
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  5. Magical Realist Valued Senior Member

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    Yes..I know hydrogen and oxygen together are flammable. I said as much. Again, why is water, the combination of hydrogen and oxygen as H2O, nonflammable? What makes a gas flammable to begin with?
     
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  7. billvon Valued Senior Member

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    Because it is relatively nonreactive. Are you saying that since it has oxygen and hydrogen _in_ it it should be flammable?

    Classically, its ability to bind with oxygen with significant heat energy liberated in the process, generally at higher temperatures.
     
  8. origin Trump is the best argument against a democracy. Valued Senior Member

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    Oxygen is typically in the form of 2 oxygen atoms so it is molecular oxygen O2. The same is true of hydrogen. Electron orbitals are most stable when the electrons are paired. Each of the hydrogen atoms has an unpaired single electron. Each oxygen atom has 2 unpaired electrons. Knowing these facts it makes sense that hydrogen and oxygen are usually in the form of H2 and O2 because they can pair up their electrons. H2O has a lower energy state (or is more stable) than O2 and H2, that is if the unpaired electrons in an oxygen atoms are paired with the unpaired electron in 2 hydrogen atoms this is a lower energy state than one O2 molecule and 2 H2 molecules.

    So if you fill a room with 50% H2 why doesn't it just blowup. The reason is that the hydrogen and oxygen are relatively stable because they have paired their electrons by forming O2 and H2. So all you have to do is add a little bit of energy to break the bonds of the O2 and H2 and they will combine to form the lower energy molecule H2O. The lower energy means energy is released (an exothermic reaction). The released energy breaks more O2 and H2 which combine to form H2O releasing even more energy breaking more bonds, etc, etc. This all happens extremely fast resulting in the case of 50% hydrogen - and explosion.

    So this also answered why water isn't reactive - it is already at a very low energy, that is it is very stable. It takes a lot of energy to break the molecules apart but can be done by electrolysis for instance.
     
    Last edited: May 16, 2014
  9. Russ_Watters Not a Trump supporter... Valued Senior Member

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    Water is what you get after it burns.
     
  10. Read-Only Valued Senior Member

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    Yes. Water is the ASH of hydrogen burning (oxidizing). You don't expect ash to burn, do you MR?
     
  11. Kittamaru Now nearly 40 pounds lighter. Staff Member

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    Chemistry is a bitch like that... looking at it macroscopically, some of these things make no sense. once you look at the molecular bonds and such though, it makes much more sense

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  12. wellwisher Banned Banned

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    Oxygen is an electron acceptor, while the fuel of the flame is an electron giver. Flammability is connected to the movement of electrons from the fuel, to the oxygen acceptor. Water, as one product of combustion, can neither accept or give electrons to oxygen or fuel, so it is not reactive with oxygen or fuel and therefore will not burn.

    The movement of electrons does not go directly from fuel to oxygen, but rather occurs through intermediate states called free radicals. These free radicals are not stable, but nevertheless represent short term step down energy states for the electrons, between the reactants and products.

     
  13. origin Trump is the best argument against a democracy. Valued Senior Member

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    The difference of just one electron in an element is actually pretty startling. For instance metalic sodium is very reactive.

    Look what happens when a piece is dropped in water. (from the site: http://www2.uni-siegen.de/~pci/versuche/english/v44-1-1.html)

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    Chlorine gas is very deadly. For example it can be used as a weapon of mass destruction:

    (Reuters) - Syria may have used chemical weapons involving chlorine in 14 attacks in recent months, French Foreign Minister Laurent Fabius said on Tuesday, expressing concerns that Syrian President Bashar al-Assad is hiding toxic weapons.

    If you add 1 electron to a Sodium atom and remove 1 electron from a Chlorine atom you have this:

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  14. KitemanSA Registered Senior Member

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    Is oxygen flammable? Yes, in away, but it requires special circumstances.
    Basically, something is flammable when it can oxidize rapidly as with a flame. Very high pressure O2 can burn to O3 with the right catalyst and ignition source. But most people won't think of that as flammability.
     
  15. KitemanSA Registered Senior Member

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    I think that in the presence of fluorine, it is.

    2H2O + 2F2 > 4HF + O2

    No?
     
  16. sideshowbob Sorry, wrong number. Valued Senior Member

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    Is the Titanic sinkable? Not any more. It already sunk; it can't sink any deeper.
     
  17. exchemist Valued Senior Member

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    Out of all the replies THIS is the one that best encapsulates the answer.
     
  18. KitemanSA Registered Senior Member

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    Except that it is not correct.
     
  19. Read-Only Valued Senior Member

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    Except that it certainly IS! How many years have you spent as a chemist? I'm betting NONE.
     
  20. exchemist Valued Senior Member

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    The Enthalpy of Formation of ozone from diatomic oxygen is +143kJ/mol : http://butane.chem.uiuc.edu/pshapley/GenChem2/A9/1.html

    So there is not a snowball's chance in hell that O₂ will "burn" to O₃, whether catalysed or not.

    You need to dissociate O₂ into atomic oxygen first, which involves putting in a lot of energy. In the upper atmosphere this occurs by photolysis, i.e. absorption of a UV photon.
     
  21. Read-Only Valued Senior Member

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    That's absolutely not true. It's pretty obvious that you have NEVER really studied chemistry!
     
  22. exchemist Valued Senior Member

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    It is true that this reaction occurs quite violently, but it would not normally be referred to as "burning".

    The term "burning" generally refers to a strongly exothermic and self-sustaining reaction of a substance with oxygen, characterised by flames (emission of light).
     
  23. Kittamaru Now nearly 40 pounds lighter. Staff Member

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    Oxygen, technically speaking, is not flammable... it is an oxidizer. If you had a room with non-reactive sides, filled with 100% O2 and nothing else, no other gases, it would not be possible to ignite it.

    Now, high oxygen environments are easily flammable. Take Apollo 1 for example - the high oxygen environment in the flight capsule, coupled with the plethora of combustible materials (velcro, the insulation on the wires, etc) were so much more flammable in the pure oxygen environment - this is because Nitrogen is non-reactive and will actually help snuff-out a fire.
     

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