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# Purdue - CHE 211 - Class Notes

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Purdue - CHE 211 - Class Notes

##### Description: Vapor liquid equilibrium for mixtures On page 5 of the review session notes, we wrote the following equation: ???? ???? ???? ???? ???? ???? Then, the left hand side was simplified using the Lewis fugacity rule and the right hand side was expressed using the Lewis/Randall reference state as below: ???? ???? ????????∅ ???? = ???? ???? ???? ???? ???? However, it should be noted that the Lewis fugacity
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Vapor liquid equilibrium for mixtures    On page 5 of the review session notes, we wrote the following equation:  𝑓̂ 𝑖 𝑣 = 𝑓̂ 𝑖 𝑙   Then, the left hand side was simplified using the Lewis fugacity rule and the right hand side was  expressed using the Lewis/Randall reference state as below:  𝑦 𝑖 𝑖 𝑣 𝑃 = 𝛾 𝑖 𝑥 𝑖 𝑓 𝑖 𝑜   However, it should be noted that the Lewis fugacity rule is  not always  applicable for the vapor  state. Whether the Lewis fugacity rule is applicable or not is dependent on type of interactions the  gas phase molecules undergo (Koretsky pg. 411 and 412) and these interactions are represented in  the given equation of state for the vapor phase. For example, the Lewis fugacity rule works  (∅ ̂ 𝑖 𝑣 = 𝑖 𝑣 ) for the equation of state for Problem 6 on the final practice exam, but, it doesn’t work (∅ ̂ 𝑖 𝑣 𝑖 𝑣 )  for the equation of state for Problem 4 on Homework 12. You can determine if the Lewis  fugacity rule works or not, based on the equation of state or it will be mentioned to you in  the problem. Also, Koretsky (pg. 412) mentions that Lewis fugacity rule can be considered to be  valid for species a, in a binary mixture of a and b, if –   1.  The pressure is low or the temperature is high. This condition corresponds to an ideal gas.  2.  Component a is present in large excess (y b  is small).  3.  The chemical nature of species a is similar to that of all the other components (a a  ≈ a b ).    If Lewis fugacity rule doesn’t work, then –   𝑓̂ 𝑖 𝑣 = 𝑓̂ 𝑖 𝑙   𝑦 𝑖 ̂ 𝑖 𝑣 𝑃 = 𝛾 𝑖 𝑥 𝑖 𝑓 𝑖 𝑜   ̂ 𝑖 𝑣  = some expression derived from the equation of state for the gas phase mixture.
If Lewis fugacity rule works, then –   𝑓̂ 𝑖 𝑣 = 𝑓̂ 𝑖 𝑙   𝑦 𝑖 𝑖 𝑣 𝑃 = 𝛾 𝑖 𝑥 𝑖 𝑓 𝑖 𝑜   𝑖 𝑣  = some expression derived from the equation of state for the real gas i   Writing out the full expression for liquid phase (Lewis/Randall reference state) for both cases –  𝑦 𝑖 ̂ 𝑖 𝑣 𝑃 = 𝛾 𝑖 𝑥 𝑖 𝑖 𝑠𝑎𝑡 𝑃 𝑖 𝑠𝑎𝑡 𝑒𝑥𝑝 ( 𝑉 𝑚 𝑙 𝑅𝑇 (𝑃 − 𝑃 𝑠𝑎𝑡 ))       (1)…………. (Lewis fugacity rule doesn’t work)  𝑦 𝑖 𝑖 𝑣 𝑃 = 𝛾 𝑖 𝑥 𝑖 𝑖 𝑠𝑎𝑡 𝑃 𝑖 𝑠𝑎𝑡 𝑒𝑥𝑝 ( 𝑉 𝑚 𝑙 𝑅𝑇 (𝑃 − 𝑃 𝑠𝑎𝑡 ))      (2)…………. (Lewis fugacity rule works)    Writing out the full expression for liquid phase (Henry’s reference state) for both cases –  𝑦 𝑖 ̂ 𝑖 𝑣 𝑃 = 𝛾 𝑖 𝑥 𝑖 𝐻 𝑖                                                             (3)…………. (Lewis fugacity rule doesn’t work)  𝑦 𝑖 𝑖 𝑣 𝑃 = 𝛾 𝑖 𝑥 𝑖 𝐻 𝑖                                                          (4)…………. (Lewis fugacity rule works)    Ideal mixtures:  If the vapor phase is ideal then –   ̂ 𝑖 𝑣 = 1 , ∅ 𝑖 𝑣 = 1, ∅ ̂ 𝑖 𝑣 = ∅ 𝑖 𝑣  (Lewis fugacity rule works)    If the liquid phase is ideal then –  𝛾 𝑖 = 𝛾 𝑖 𝐿𝑅 = 1 , 𝛾 𝑖 𝐻 = 1   𝑖 𝑠𝑎𝑡 = 1, 𝑒𝑥𝑝 ( 𝑉 𝑚 𝑙 𝑅𝑇 (𝑃 − 𝑃 𝑠𝑎𝑡 )) = 1

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##### Description: Vapor liquid equilibrium for mixtures On page 5 of the review session notes, we wrote the following equation: ???? ???? ???? ???? ???? ???? Then, the left hand side was simplified using the Lewis fugacity rule and the right hand side was expressed using the Lewis/Randall reference state as below: ???? ???? ????????∅ ???? = ???? ???? ???? ???? ???? However, it should be noted that the Lewis fugacity
3 Pages 34 Views 27 Unlocks
• Notes, Study Guides, Flashcards + More!
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