Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Can O2 combine with H2 to form water without activation energy?

  1. May 31, 2014 #1
    Let say that I have hydrogen gas and oxygen gas mix together, is there any chance that some H2 and O2 will react to form water without doing anything to it? I know that there needs to be activation energy to start the reaction, but are there any chance of reaction happening without activation energy? Thank you
     
  2. jcsd
  3. May 31, 2014 #2

    hilbert2

    User Avatar
    Science Advisor
    Gold Member

    Even at room temperature, some small fraction of the gas molecules has high enough kinetic energy to react with each other (look up Boltzmann distribution). However, the fraction is very small and the reaction would probably take literally billions of years at room temp.
     
  4. May 31, 2014 #3
    Thank you, so in lower temperature the less probability of H2 and O2 combining is lower because the gas molecule with high kinetic is less than high temperature, did I understand it correctly?
     
  5. May 31, 2014 #4

    hilbert2

    User Avatar
    Science Advisor
    Gold Member

    Yes, the reaction rate is proportional to ##e^{-\frac{E_{a}}{kT}}##, where ##E_{a}## is the activation energy and ##k## is the Boltzmann constant. Because of the behavior of the exponential function, the reaction rate very rapidly becomes slower when temperature is decreased.
     
  6. May 31, 2014 #5
    Thank you, now I understand
     
  7. Jun 7, 2014 #6
    No, you still need activation energy.

    [itex]2~H_{2}(g)+O_{2}(g)~\xrightarrow{\Delta}~2~H_{2}O(g)~\ \ \ \ \ \ \ \ \ \ \Delta H^{\circ}=-483.6~kJ~mol^{-1}[/itex]
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Can O2 combine with H2 to form water without activation energy?
  1. Combining H2 with 0 (Replies: 8)

  2. H2o o2 energy (Replies: 1)

Loading...