Lec-18-Chap10-2-Complete

Lec-18-Chap10-2-Complete - Lec-18-Chap10-2-Complete...

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Lec-18-Chap10-2-Complete 10/14/2011 Colligative properties. 1 Lec-18: Solutions, Concentration Variables and Colligative Properties Chapter 10 1 Review Session for Second Exam Friday, October 14, 6:00 – 9:00 PM Harriman Hall 137 Please fill your midterm course evaluations Deadline is on Sunday October 16 Vapor Pressure, Boiling and Freezing points of Solutions Colligative Properties: properties that do not depend on the nature of the solute or the solvent, but rather depend only on the number of dissolved solute particles (molecules or ions). Examples of colligative properties are 1. Vapor pressure lowering. 2. Boiling point elevation. 3. Freezing point depression. 4. Osmotic pressure. 2 In the following we use the labels: ; 2 1: : solv so ent lute
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Lec-18-Chap10-2-Complete 10/14/2011 Colligative properties. 2 Colligative Properties: Vapor Pressure Lowering At temperatures above the temperature of the triple point a pure liquid can coexist with its vapor. 3 Colligative Properties: Vapor Pressure Lowering At temperatures above the temperature of the triple point a pure liquid can coexist with its vapor. 4
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Lec-18-Chap10-2-Complete 10/14/2011 Colligative properties. 3 Dissolution of Gases in Liquids Because the addition of solute to a solution makes x 1 <1 we have that P 1 < P 1 °. Addition of an amount of solute changes the vapor pressure of the solvent, according to Raoult’s law 0 1 1 1 P P x where P 1 is the vapor pressure of the solvent above the solution and P 1 ° is the vapor pressure of the pure solvent at that temperature . x 1 is the mol fraction of the solvent in the solution.   0 0 0 0 1 1 1 1 0 0 0 1 1 1 1 11 2 relative decrease of the vapor pressure of the 1 solvent x P P P P P P P P x x    5 Dissolution of Gases in Liquids We can easily see that that the magnitude of the relative decrease of the solvent vapor pressure is proportional to the number of particles of the solute in the solution. 0 1 1 2 0 1 P P P x We found that Considering x 2 : in the case of a dilute solution we have 22 2 0 1 0 1 2 1 number of particles of the solute in the solution P P nn P xN n N 6
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Lec-18-Chap10-2-Complete 10/14/2011 Colligative properties. 4 7 1)
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This note was uploaded on 03/06/2012 for the course CHE 132 taught by Professor Hanson during the Fall '08 term at SUNY Stony Brook.

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Lec-18-Chap10-2-Complete - Lec-18-Chap10-2-Complete...

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