Lecture_05

In other words the partial pressure of a substance in

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Unformatted text preview: apor pressure of pure A as PA* and that of B as PB*. Raoult’s law can now be written as PA = xAPA* and PB = xBPB*. In other words, the partial pressure of a substance in the vapor phase is determined by its mole fraction in the liquid phase. Compare this to the Dalton’s law of partial pressures, which states PA = yAP and PB = yBP, where the total pressure is denoted as P. If only A and B are present in the gas phase above the solution, we have P = xAPA* + xBPB*. Since A and B are the only substances present in solution, we may re-write this as P = xAPA* + (1 – xA)PB*, which gives the variation of total pressure as a function of xA Problems 5.19, 5.21, 5.28. . 4 Henry’s Law: Henry’s Law may be written in terms of molality, molarity or mole fractions as PB = kBmB ≈ kB″cB ≈ kB′xB. In the limit of infinite dilution, solvents usually follow Raoult’s law and solutes usually follow Henry’s law. The form of Henry’s law preferred by the authors of the textbook is: PB = kB′xB, (5.28) where B refers to the component present in small amounts in the solution. One place w...
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This document was uploaded on 02/28/2014 for the course CHEM 311 at LA Tech.

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