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Unformatted text preview: Lecture 22 1 Nonideal Solutions; What makes a Solute? (24.59) Intermolecular interactions between different molecules usually are not the same as the interaction in pure liquids. Fig 24.9 For these three alcohols in water there are large deviations from ideal behavior as x ROH 0. Why? As Rgroup gets larger, less favorable waterROH interaction, since R groups are hydrophobic, but as x ROH 1, interactions are basically ROH … ROH and we get ~pure material, ideal behavior: * ROH ROH P x P = alc Yet in the "nonideal" region as 0, P . Why? ROH ROH x x O Alcohol is surrounded by water, so there is a uniform (but nonideal) interaction between ROH and water: ( 29 * , , Henry's Law ROH H ROH ROH H ROH ROH P k x k P = = MeOH EtOH 1proponol Lecture 22 2 * 1 1 1 1 1 1 1 ,1 In general: as 1, as 0, H x P x P x P x k O = O = In general for a two component system, Henry’s law behavior will be a consequence of Raoult’s law. 1 1 2 2 0 GibbsDuhem eqn. (T,P const) x d x d μ μ + = ( 29 , ln ln , 1,2 i i i i i i i T P P T RT P d RT dx i x μ μ μ 1 = + = = 1 ( 29 1 2 1 1 2 2 1 2 1 2 , , 1 2 1 2 1 2 , , ln ln 0 plug in ln ln T P T P T P T P P P x dx x dx dx dx x x P P x x x x 1 + = =  1 1 = 1 Lecture 22 3 * 1 1 1 1 If 1 obeys Raoult's law, then as 1, x P x P O = * * 1 1 1 1 1 1 * 1 1 1 ln 1 as 1 x P P x x x x x P 1 = = 1 2 2 1 2 2 , ln so 1 as 1 or T P P x x x x 1 = 1 2 2 2 2 2...
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This note was uploaded on 04/13/2008 for the course CHEM 444 taught by Professor Jameslis during the Spring '08 term at University of Illinois at Urbana–Champaign.
 Spring '08
 JamesLis
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