Chapter 7 : Slide 1

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Chapter 8 Phase Diagrams
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OUTLINE SECTION 8.1 -Definitions SECTION 8.2
-The Phase Rule SECTION 8.3 -Two Component Systems
HOMEWORK EXERCISES 8.4,8.5,8.6 parts (a) only
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Definitions

• Phase A state of matter that is uniform
  throughout in both chemical composition and
  physical properties. Given the symbol P.
• Component A chemically independent constituent
  of a system. Given the symbol C.
• Variance Is the number of intensive variables
  that can be changed independently without
  disturbing the number of phases in equilibrium.
  Given the symbol F.

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The Phase Rule
The phase rule relates the number of components,
phases and independent intensive variables F
C P 2
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Consider the Phase diagram for water.
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Two-component systems
C 2, F 4 - P

• The maximum number of independent variables, F,
  is 3
• (one phase). These are temperature, pressure and
  composition.
• We generally look at the behavior of two
  component systems by either
• Keeping T constant and seeing how the composition
  varies with p.
• Keeping p constant and seeing how the composition
  varies with T.

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Vapor Pressure diagrams
The partial vapor pressures of the components of
an ideal solution are related to the composition
by Raoults Law pA xApA pB xBpB
Now, p pA pB and xA xB 1 so p pB
(pA - pB) xA
The composition of the vapor The mole fractions
in the gas phase , yA pA/p and yB pB/p,
hence
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Vapor Pressure diagrams
Mole fraction of A in vapor, yA
Mole fraction of A in liquid, xA
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Vapor Pressure diagrams
Pressure
Composition
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Temperature composition diagrams
Simple Distillation
Temperature
Composition
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Temperature composition diagrams
Azeotropes
Temperature
Composition
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Liquid-liquid phase diagrams
Temperature
Composition