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Spontaniety of gas(Nitrogen) adsorption over solid(Zeolite).

  1. Jul 12, 2012 #1
    Hello!

    The other day I was reading about adsorption(gas over solid), and there it stated that it is a spontaneous process. I wanted to know how spontaneous the process is. I therefore took nitrogen adsorption over zeolite as a candidate to find its spontaneity, and to my surprise, my calculations showed it to be a non-spontaneous process. I guess I am wrong somewhere, but I just cannot find where.

    Following are the calculations that I did;
    dG = dH - T*dS
    Assuming adsorption to be equivalent to converting gas to liquid.
    Therefore,
    dH = Heat of vaporization of Nitrogen = -5560J/mole
    T = 300K (Adsorption at 300K).
    S1 = Entropy of Nitrogen at 300K = 192J/moleK.
    S2 = Entropy of Nitrogen in liquid form (I did not find entropy data of liquid Nitrogen, but I did find data at 100K) = 160J/moleK.

    Which gives,
    dG = 4040J/mole - non-spontaneous.

    I saw a graph which showed quite a lot of adsorption at 300K.

    I speculate that, adsorption needs pressure and the source of this pressure has more than enough negative dG?

    Could you please help me understand this?

    Thanks!
     
  2. jcsd
  3. Jul 13, 2012 #2
    No reply? Not even an opinion?
     
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