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Hydrogen Balloons

  1. Mar 22, 2005 #1
    If you were to explode two different balloons, one filled with H2 gas and another filled with a mixture of H2 and O2 gasses in a 2:1 volume ratio, which balloon would have a much larger fireball associated with it and why?
    Also, why is it necessary to start the reaction with a flame?

    Would the H2 balloon have the largest fireball because of its higher concentration of hydrogen gas?
    I was thinking that starting the reaction with a flame heats things up creating a faster movement of molecules. The faster movement of molecules means a higher velocity for collision creating the explosion. Is this correct?
  2. jcsd
  3. Mar 22, 2005 #2


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    Staff: Mentor

    Pure hydrogen will not explode nor burn without oxygen, so you will get only reaction on the surface. Mixture 1:2 has optimal proportions so the reaction will take place in whole volume almost instantly.

    How it translates into fireball I have no idea.

    Your answer for the second question sounds OK with me, unless you are asked at your PhD exam :)

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  4. Mar 22, 2005 #3


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    assumming both balloons had equal volumes of total gas, that would mean that the balloon containing pure H2 would (although take logner to compleatly combust), create a bigger fireball because the is more hydrogen to burn, bigger explosion, I dont think that the speed of reaction is all that noticible on a small of scale as a ballon, both seem pretty instantaneuos to the naked eye.

    you need to start it off with a flame, since the both together wont react/combust by themselves, they might slowly combine to form water, but wont (necesarly, under normal conditions) explode by themselves, something must set it off.
    You could set it off by another means, say a very hot heating element, but a flame is a very simple and effective way of both starting the reacting and breaking/melting the ballon to allow air (and oxygen) to join in on the reaction.
  5. Mar 22, 2005 #4
    Which balloon reaction is going to result in the largest increase in entropy of the surroundings and why?

    Does the H2 filled balloon give off a higher heat content than the H2/O2 balloon?
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