1. Multicomponent systems
Doba Jackson, Ph.D.
Huntingdon College

2. Problem 1: Acetone has a normal boiling point of 56. 2
Problem 1: Acetone has a normal boiling point of 56.2*C and a molar enthalpy of vaporization of kJ/mol. Calculate the equilibrium vapor pressure of acetone at 20.0*C.

3. Problem 2: The vapor pressure of bromine is 133 torr at 20. C and 48
Problem 2: The vapor pressure of bromine is 133 torr at 20.0*C and 48.1 torr at 0.00*C. Calculate the enthalpy of vaporization of bromine.

4. Chemical Potentials of Liquids and liquid mixtures
Θ is pressure at 1 bar
* is pressure of pure A
Rauolt’s Law
Rauolt’s law states that the chemical potential
of the liquid is altered by the presence of a solute.
The amount of the deviation is based on the mole
fraction of the solute.

5. Ideal Solutions
Ideal solutions are solutions that obey Rauolt’s law throughout its composition range from pure A to pure B.

6. Rauolt’s Law is observed when two solutions have similar structures
Obey’s Rauolt’s Law
Does not obey’s Rauolt’s Law

7. Dilute solutions typically do not obey Rauolt’s Law but follows Henry’s Law
Θ is pressure at 1 bar
* is pressure of pure A
Henry’s Law
Henry’s law states that the chemical potential
of the liquid is altered by the presence of a solute.
The amount of the deviation is based on the mole
fraction of the solute.

8. Vapor-Pressure Lowering of Solutions: Raoult’s Law
The vapor pressure of pure water at 25 °C is mm Hg. What is the vapor pressure of a solution made from 1.00 mol glucose in 15.0 mol of water at 25 °C? Glucose is a nonvolatile solute.
Psoln = Psolv Xsolv
= 22.3 mm Hg
1.00 mol mol x
23.76 mm Hg
15.0 mol =

9. Basis for Rauolt’s and Henry’s Law
Rauolt’s Law
Henry’s Law

10. General model of solutions

11. Problem 5.24a
It is found that the normal boiling point of a binary solution of A and B with XA=.6589 is 88*C. At this temperature the vapor pressures of pure A and B are kPa and kPa, respectively.
(a) Is the solution Ideal?
(b) What is the composition of the vapor above the solution mixture?

12. Temperature-composition diagrams
Distillation- separation of mixtures by withdrawing the more volatile component in the vapor phase.
Theoretical plates- number of vaporization-condensation steps required to achieve a given composition.

16. Theoretical Plates # of Theoretical Plates depend on several factors:
Temperature
Distillation Apparatus
Composition
Vaporization temp. difference
Azeotropes
-Amount of each phase can be
determined by the lever rule

17. Types of Phase Diagrams
Vapor Pressure-Composition Diagrams
Upper Liquid Phase (P=1)
Bi-Phase intermediate (P=2)
Lower Vapor Phase (P=1)
Liquid-Composition Diagrams
Upper vapor Phase
Bi-Phase intermediate
Lower vapor Phase
Two miscible liquids
Two partially miscible liquids
Azeotropic composition

18. Liquid-only Phase diagrams
Upper consolute temp. (Tuc)-
Is the temperature at which
both liquids are miscible.
Inside the circle, two phases
exist.
Each composition is given
by the lever rule.
Hexane-Nitrobenzene

19. Liquid-only Phase diagrams
Water-Triethanolamine
Lower consolute temp. (Tlc)-
Is the temperature at which
both liquids are miscible.
Inside the circle, two phases
exist.
Each composition is given
by the lever rule.

20. Liquid-only Phase diagrams
Lower consolute temp. (Tlc)-
Is the temperature at which
both liquids are miscible.
Inside the circle, two phases
exist.
Each composition is given
by the lever rule.
Water-Nicotine solution

21. Liquid-only Phase diagrams

22. A temperature-composition diagram in which boiling occurs before the solution becomes miscible

23. Colligative Properties
Colligative Properties- properties of solutions that depend only on the number of molecules present in a volume of solvent and not on the identity of the solute.
Vapor Pressure lowering
Boiling Point Elevation
Freezing Point Depression
Osmosis

24. Osmosis Osmosis: the spontaneous
passage of a pure solvent into
a solution while separated by a
semi-permeable membrane.
- Cell membrane transport
- Dialysis
- Blood Transfusions
- Osmometry (M.W. determinations)
Osmotic Pressure (π): the pressure required to stop the
influx of solvent.

25. Calculation of Osmotic Pressure
Fundamental Equation;
Assume const. Temperature
Change in pressure is due to solute
concentration in the solution.

26. Calculation of Osmotic Pressure
Assume the solute
concentration is small
Molar
Concentration