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Deviation of a gas from ideal gas behaviour

  1. Mar 6, 2015 #1
    Hi all, I have a question from a tutorial sheet that I'm stuck with. The question is

    Estimate the pressure at which a gas of argon atoms, at a temperature of 300 K, will begin to show deviations from the ideal gas behaviour due to the finite size of the atoms. Answer: Of order 10^9 Pa.

    So I tried taylor expanding the hard sphere gas equation: P'(V-b)=NkT, to get P'=P(1+b/V) to first order, where P is the ideal gas pressure. However, I don't know if this is the right approach or just what to do next really. Could someone point me in the right direction please?
     
  2. jcsd
  3. Mar 7, 2015 #2

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    What magnitude of deviations?
    Please check this number --- it's somewhat beyond ridiculous.
     
  4. Mar 8, 2015 #3
    It just says deviations & that's the answer given
     
  5. Mar 8, 2015 #4
    It just says deviations & that's the answer given
     
  6. Mar 8, 2015 #5

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    Without some specification of magnitude of departure, there's no way to answer the question. You could make an assumption of 0.1% (or 0.3 to perhaps 1 % for ordinary measurement accuracies), and at the fixed temperature calculate a pressure at which the excluded volume reached that value, but you're never going to see 109 Pa for such a calculation.
     
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