Ok, let's say we have at our disposal a thermometer of constant volume gas.(adsbygoogle = window.adsbygoogle || []).push({});

Inside it, we'll put a real gas, like Helium or Molecular Hydrogen. Ok, the gas compartment is placed inside a mixture of liquid water and ice, so we guarantee the gas inside is at 273.15 K. We measure its pressure (from a Hg column bar), and annotate it. Let's say the value is Pm, pressure for molten ice.

We repeat the process, but this time we place the gas into a mixture of boiling water, so we guarantee the gas will be at 373.15 K. We also register its new pressure, let's call it Pb, pressure for the gas in contact with boiling water.

Ok, after we do that, we are interested in the fraction y = Pb/Pm, for that real gas. Of course this y will vary depending on the number of mols of the real gas in the compartment, let's call it n. But we could, in theory, make a graph of y X n, or maybe y X Pm, which would look similar (the graphs will be equivalent).

We could make this graph for various substances, like H2, O2, N2, He.

Now is the main part: if there were an ideal gas in the compartment, the rate Pb/Pm would be a constant, since the volume is constant, and it would be yIdeal = 1.3661.

The question is: is it possible for any real gas, like H2, in any circumstance, to have Pb/Pm smaller than 1.3661, the value for the perfect gas? Or is it just impossible?

Thanks in advance

Astronauta

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# Limits of Real Gas Behavior

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