Lecture_7_091608

Lecture_7_091608 - Lecture 7 September 16, 2008 Failings...

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Page 1 of 12 Lecture 7 – September 16, 2008 Failings and Success of van der Waals, Lever Rule, Law of Corresponding States, Work Last Time Show the expressions, 2 c b 27 a p = , b 3 V c = , Rb 27 a 8 T c = Hence: 2 c c V p 3 a = , 3 V b c = , c c c T 3 V p 8 R = , and 375 . 0 8 3 RT V p Z c c c c = = = Reality for van der Waals Eq. of State • Although it is better than the perfect gas law, there is no experimental validation • Only predicts phase behavior (gas to liquid transition), qualitatively • Does predict T c • Fails quantitatively Hence, other equations of state like the virial expansions and those found in Table 1.7 do better jobs of predicting real gas behavior.
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Page 4 of 12 (1) For a given T in the coexistence region A gas ρ = ρ B liquid ρ = ρ (2) Amounts of gas and liquid vary according to the overall molar density ρ which lies between ρ A and ρ B . Lever Rule to obtain amounts g g g g N V 1 V = ρ = , where ρ is molar density l l l l N V 1 V = ρ = and total total N V 1 V = ρ = Below T c in the two phase region l ρ < ρ < ρ g and at critical point, l ρ = ρ = ρ g at g ρ = ρ , infinitesimal amount of l ρ at l ρ = ρ , infinitesimal amount of g ρ What are g x and l x (mole fraction)? N V V N V 1 V g total total l + = = ρ = Noting that ࢓ࢋࢇ࢔࢙ ࢂ ൌࡺ &
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This note was uploaded on 09/29/2008 for the course CHEM 3615 taught by Professor Aresker during the Fall '07 term at Virginia Tech.

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Lecture_7_091608 - Lecture 7 September 16, 2008 Failings...

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