Ideal Gas Law Equilibrium Requirements

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The ideal gas law is not valid under non-equilibrium conditions, such as during the free expansion of an ideal gas. In free expansion, the velocity distribution of gas particles deviates from the Maxwell-Boltzmann distribution due to the lack of interactions at the boundaries of the gas cloud. Fast-moving particles escape outward while slower particles lag behind, disrupting the equilibrium state. This results in a changing ratio of fast to slow molecules, leading to a non-Maxwellian distribution. Overall, the complexities of particle interactions and velocity distributions challenge the applicability of the ideal gas law in such scenarios.
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It is well known that the ideal gas law applies only to an ideal gas, one consisting of particles infinitesimal in size and exhibits no interactions between the particles. Considering an ideal gas, is the ideal gas law valid under non-equilibrium conditions? For example, does the ideal gas law hold for all instants of in the free expansion of an ideal gas?

References, if available, would be appreciated.
 
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"Free"expansion? How do you define volume for such a condition? PV = MRT is then not valid.
The Maxwell-Boltzman distribution is not valid either. Let's assume the expansion of a Ne
gas volume starts from an initial equilibrium state. At say 20 C the Ne atoms have an average
velocity of ~850m/s, but there are atoms with velocities close to 0 m/s and some which
move at over 2000 m/s. Clearly in a "free" expansion the velocity distribution at the boundaries of the
expanding Ne cloud will not be Maxwellian.
 
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Kazys, thank you. But why is it that "the velocity distribution at the boundaries of the gas will not be Maxwellian" in a "free" expansion?
 
My answer is simplistic, and because of that chances are that it is correct. Consider the Ne cloud before its free expansion. Within the could
the molecules interact, the probability is that fast ones loose energy, slow ones gain it. Equilibrium is maintained. At the edges the fast
molecules move faster in all directions including the outward directions. There they do not interact but keep moving. The slow ones
tag behind. Consequently the ratio of fast to slow molecules changes, thus it is no longer Maxwellian.
 
Thanks Kazys - this makes sense. As an aside, you are referring to Occam's razor, when you say the simple answer is usually the correct one, right?
 
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