Lecture23A(2) - Lecture 23 1 Solid-Liquid Solutions...

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Unformatted text preview: Lecture 23 1 Solid-Liquid Solutions Non-electrolytes (Chapter 25.1-4) We started last week with slightly soluble liquids (solutes) in solvents. Now we will treat more formally: solvent=component #1, solute (solid)=component #2. 1 1 * 1 1 1 1 Raoult's standard state: Recall: as 1 P a P a x x = 1 4 4 2 4 4 3 2 2 , 2 2 2 Henry's standard state: as x H x P a k a x x = 1 4 442 4 4 43 x represents mole fraction scale Note that while P 2 may be very small, k H,x may be small as well such that P 2 /k H,x is finite. For solutes there are two other standards to use as the solute goes to zero. Mole fractions are large units, so we will consider standards that are appropriate for small amounts of solute. 1 st As we all know, one standard of measure is molarity (concentration) for a solute: 2 moles of solute, n L of solvent c a 2 2 2 , as c 0; c c H c P a c a k a = While this is quite useful, there is a problem. Molarity, c, is temperature dependent because solvent volume is T-dependent! Lecture 23 2 2 nd A more useful concentration unit is molality, m: 2 solvent n m kg a Mass of solvent is T-independent. 2 2 2 , as 0; m m H m P a m m a k a = It is easy to switch between these measures. For the solvent the number of moles in 1 kg is ( 29 1 1000 / / g kg M g mol where M 1 is the molecular weight in g/mol....
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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.

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Lecture23A(2) - Lecture 23 1 Solid-Liquid Solutions...

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