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The Van der Waals equation (P+an^2/V^2)(V-nb) = nRT looks a bit like the ideal gas law, except for two correction terms. The first term (an^2/V^2) arises from the real intermolecular attraction that two of the same molecules have for one another (remember in the ideal gas law, the two assumptions made are that gases have no volume and are non-interacting). It is an additive term because interactions tend to lower the pressure (rearranging, P=nRT/(V-nb) - an^2/V^2). The "a" constant is specific to a particular gas, and reflects its strength of intermolecular interaction. The second term (nb) arises from the real volume that molecules have. The true volume of the system is larger than expected, so it is a negative term (that is, you have to subtract the true volume of the molecules from the system to account for them). as a result, the "b" constant relates to molecular "size" Then, the answer to your question is "yes". When the "a" and "b" terms are removed (assumed to be zero), you end up with the Ideal Gas Law, which is a generalization for all gases (non-specific). Please feel free to email with further questions at weibelm@battelle.org best regards, Mike

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