1. Solution Properties 11.1 Solution Composition
11.2 The Energies of Solution Formation
11.3 Factors Affecting Solubility
11.4 The Vapor Pressures of Solutions
11.5 Boiling-Point Elevation and Freezing-Point Depression
11.6 Osmotic Pressure
11.7 Colligative Properties of Electrolyte Solutions
11.8 Colloids

2. An Aqueous Solution and Pure Water in a Closed Environment

3. Liquid/Vapor Equilibrium

4. Vapor Pressure Lowering: Addition of a Solute

5. Colligative Properties
Lowering of solvent vapor pressure
Freezing-point depression
Boiling-point elevation
Osmotic pressure
Colligative properties depend only on the number, not on the identity, of the solute particles in an ideal solution.

6. Lowering of Solvent Vapor Pressure
The presence of nonvolatile solute particles lowers the number of solvent molecules in the vapor that is in equilibrium with the solution.
The solvent vapor pressure is lowered;
Assuming ideal behavior, the lowering of vapor pressure is proportional to the mole fraction of solute:
DP = Xsolute.Posolvent (for nonelectrolytes)
= iXsolute.Posolvent (for electrolytes)
(i is the van’t Hoff’s factor, which approximately relates to the number of ions per formula unit of the compound)

7. Changes in Boiling Point and Freezing Point of Water

8. Freezing-Point Depression
When a solute is dissolved in a solvent, the freezing point of the solution is lower than that of the pure solvent.
ΔT = Kfmsolute (for nonelectrolytes)
= iKfmsolute (for electrolytes)
ΔT = freezing-point depression
Kf = freezing-point depression constant
msolute = molality of solute

9. Freezing Point Depression: Solid/Liquid Equilibrium

10. Freezing Point Depression: Addition of a Solute

11. Freezing Point Depression: Solid/Solution Equilibrium

12. Boiling-Point Elevation
Nonvolatile solute elevates the boiling point of the solvent.
ΔT = Kbmsolute
ΔT = boiling-point elevation
Kb = boiling-point elevation constant
msolute = molality of solute

13. Boiling Point Elevation: Liquid/Vapor Equilibrium

14. Boiling Point Elevation: Addition of a Solute

15. Boiling Point Elevation: Solution/Vapor Equilibrium

16. Exercise #1
What mass of ethylene glycol (C2H6O2), in grams, must be added to 1.50 kg of water to produce a solution that boils at 105oC?
(Boiling point elevation constant for water is Kb = 0.512oC/m)
At what temperature will the solution freeze?
(Freezing point depression constant for water is Kf = 1.86oC/m)

17. Osmotic Pressure = MRT = osmotic pressure (atm)
Osmosis – flow of solvent into the solution through a semipermeable membrane.
= MRT
= osmotic pressure (atm)
M = molarity of the solution
R = gas law constant
T = temperature (Kelvin)

19. Osmosis

21. van’t Hoff Factor, i
The relationship between the moles of solute dissolved and the moles of particles in solution is usually expressed as:

22. Modified Equations for the Colligative Properties of Electrolytes

23. Examples
The expected value for i can be determined for a salt by noting the number of ions per formula unit (assuming complete dissociation and that ion pairing does not occur).
NaCl i = 2
KNO3 i = 2
Na3PO4 i = 4
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24. Ion Pairing
At a given instant a small percentage of the sodium and chloride ions are paired and thus count as a single particle.

25. Ion Pairing Ion pairing is most important in concentrated solutions.
As the solution becomes more dilute, the ions are farther apart and less ion pairing occurs.
Ion pairing occurs to some extent in all electrolyte solutions.
Ion pairing is most important for highly charged ions.

26. Exercise #2
A solution was prepared by dissolving g glucose in g water. The molar mass of glucose is g/mol. What is the boiling point of the resulting solution (in °C)? Glucose is a molecular solid that is present as individual molecules in solution. °C

27. Exercise #3
When 33.4 mg of a compound is dissolved in 10.0 mL of water at 25°C, the solution has an osmotic pressure of 558 torr. Calculate the molar mass of this compound.
111 g/mol

28. Colloidal Mixtures A suspension of tiny particles in some medium.
Tyndall effect – scattering of light by particles.
Suspended particles are single large molecules or aggregates of molecules or ions ranging in size from 1 to 1000 nm.

29. Scattering of Light by Colloid Particles

30. Tyndall Effect of Colloidal Mixture

31. Tyndall Effect of Morning Mist

32. Types of Colloids

33. Micelle – A Colloidal Suspension

34. Micelle in Soap Bubbles

35. Coagulation Destruction of a colloid.
Usually accomplished either by heating or by adding an electrolyte.