Hydrogen Inversion Temperature & non-Joule Thomson cooling

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  Kaustubh Katdare

  Thread moved to Chemical/Metallurgy engineering section.
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  Voltaire

  The J-T point is basically where the gas molecule has so much kinetic energy when it is released from pressure that it heats when it expands. Consider any gas that expands at constant enthalpy such as through a hole in a pipe.
  Impulse: During a collision between two gas molecules they slow down or may, for an instant, even become stationary. This raises the average potential energy in the system and the average kinetic energy decreases, causing the gas to cool [conservation of energy]
  Intermolecular forces: (Van der Waal forces) are an array of forces that attempts to keeps molecules together, similar to gravitational forces.
  
  So, the potential energy of the escaping molecules is converted to kinetic energy because there are less collisions and the intermolecular forces diminish. In 'ordinary' gases the effect of weakening intermolecular forces overcome the effect of 'less collisions' and the gas cools. In the 'quantum' gases i.e. H, He and Ne, the 'less collisions' dominate and the gas heats up viz. less collisions equals more kinetic energy = heat.
  
  Several works approximate the critical J-T coefficient near enough to mc = Tc/6Pc