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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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- Spring '08
- Solubility, Amount of substance, Freezing-point depression