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

  1. Jul 12, 2012 #1

    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.
    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?

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