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Is Oxyhydrogen a spontaneous reaction at very high temperatures?

  1. Apr 13, 2014 #1
    Hi, this may seem like a noob question for you geeks out there, but I cant wrap my head around this.
    The formula for a spontaneous reaction is [itex]\Delta[/itex]H-T[itex]\Delta[/itex]S < 0
    Basically, since the reaction between hydrogen and oxygen gas has a negative change in enthalpy it must mean that if the temperature in Kelvin is big enough then the reaction between oxygen and hydrogen gas will not be spontaneous.

    Because the negative T multiplied with the negative change in entrophy will be more positive than the enthalpy change and it wont be a spontaneous process? right?
     
  2. jcsd
  3. Apr 13, 2014 #2

    Ygggdrasil

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    Yes, that is correct. This is one reason why performing electrolysis of water at high temperatures is more efficient than at room temperature (http://en.wikipedia.org/wiki/High-temperature_electrolysis).
     
  4. Apr 13, 2014 #3
    Ill read up on this, thanks.
     
  5. Apr 17, 2014 #4
    I'm sorry to bring this up, but does the same count for the burning of magnesium. Burning of magnesium is exothermic, but the change in entropy is negative as well so if the temp is big enough, the reaction wont be spontaneous. Correct?
     
  6. Apr 17, 2014 #5

    Ygggdrasil

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    Yes, that's correct.
     
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