1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Compare the recombination rates for 2-body and 3-body reactions (i.e. forming O2)

  1. Oct 30, 2012 #1
    1. The problem statement, all variables and given/known data

    Assume that recombination of atoms proceeds at the gas-kinetic rate of collisions. Compare the recombination rates for a 2-body and 3-body reaction, such as in the formation of O2.
    (hint: you may want to use production rate equations and calculate the number density of molecules needed for equal rates Kr2 = Kr3)

    2. Relevant equations
    (1) 2-body recombination: O + O = O2 + hv
    (2) 3-body recombination: O + O + M = O2 + M (M is an atmospheric molecule that absorbs excess energy)

    gas-kinetic rate of collsions: Kgk = sig*vo ; where sig is collisional cross section and vo is mean thermal velocity (sqrt(2kT/m), where k is boltzmann's constant, T is temp, and m is particle mass)

    The 2-body reaction rate (Kr2) is then Kgk with the above assumption.
    The 3-body reaction rate Kr3 = 2*R/vo * Kgk2

    I think the rate equations would be: (1) d[O2]/dt = [O]^2*Kgk ;
    (2) d[O2]/dt = [O]^2*[M]*Kr3

    If I set Kgk = Kr3, I end up with 2*sig*R = 1 ...which I can't make sense of

    If I equate the rate equations (assuming I derived them correctly), I get 2*sig*R*[M] = 1

    Neither way do I see a way to get at the number density. I expect that I would use the ideal gas law in some way if I could figure out how it would work into these relationships...

    for example, PV = nkT...so n/V would be number density (N); N = P/kT

    I'm totally lost here, any nudge in the right direction would be greatly appreciated

    3. The attempt at a solution
    oh, my attempt is shown above
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted



Similar Discussions: Compare the recombination rates for 2-body and 3-body reactions (i.e. forming O2)
Loading...