Lecture_05

The pressure plotted in the phase diagrams and used

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Unformatted text preview: Clausius-Clapeyron equation is applicable to solid-vapor equilibrium as well. The pressure plotted in the phase diagrams and used in these relationships is the vapor pressure of the substance under consideration, not the total pressure. Eq. (5.14) gives the P-T relationship required to plot the lines in the phase diagrams. Therefore, Eq. (5.14) for the liquid-vapor and the solid-vapor equilibria can be used to find the triple point for a one-component system. Examples 5.2, 5.3, Problems 5.1–5.4, 5.7–5.10, 5.12, 5.15, 5.18, 5.20. 2 The Gibbs Equation: By definition, dG = VdP – SdT. At constant temperature, the second term vanishes and we get dG = VdP. For the liquid vapor equilibrium considered earlier, under these circumstances, we have dGm,v = dGm,l or Vm,vdP = Vm,ldPt, where the pressure term on the vapor side is the vapor pressure of the substance while on the liquid side, it is the total pressure acting on the liquid surface. Now, using ideal gas law for the vapor, we get RT dP = V dP or m,l t P dP = V m,l dP . P RT t Now consider a situation...
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This document was uploaded on 02/28/2014 for the course CHEM 311 at LA Tech.

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