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Mixture of hydrogen and oxygen

  1. Aug 23, 2010 #1
    Does mixture of hydrogen and oxygen actually has to be ignited or the reaction occurs even without ignition when some critical H:O proportion is reached?
     
  2. jcsd
  3. Aug 23, 2010 #2

    alxm

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    Nope, it doesn't spontaneously react at any concentration.
     
  4. Aug 23, 2010 #3

    Borek

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    In theory such mixture reacts even at room temperature, albeit very slowly. But I don't have access to any kinetic data, so I have no idea whether the reaction at room temperature is observable or not.
     
  5. Aug 23, 2010 #4
    Which reminds me: if you heat the mixture continuously (starting at room temperature and gradually increasing but not to slow) at what temperature would it ignite?
     
  6. Aug 23, 2010 #5

    alxm

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    In theory, diamonds turn into graphite at room temperature, albeit very slowly :wink:

    Thank god for slow reaction kinetics - or we'd all instantly die in a ball of flame.
     
  7. Aug 23, 2010 #6
    Actually I think I've found it:

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

    "The hydrogen autoignition temperature, the temperature of spontaneous ignition in air, is 500 °C (932 °F)."

    That high! ...I would have thought it's much lower. ...No way; that must be wrong. (?)
     
  8. Aug 23, 2010 #7

    Borek

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    This is only some kind of approximation, as autoignition temperature is surely a function of the mixture composition.

    --
     
  9. Aug 23, 2010 #8

    alxm

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    Sounds about right to me.

    As Borek said, it changes a bit with composition though.
     
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