1. CH 11: Properties of Solutions
Describing Solutions – concentration units
Energetics of solution formation
Factors impacting solubility – P and T
Colligative Properties of solutions
BP elevation
FP depression
Osmotic pressure
Vapor Pressure

2. Terms Solution – homogeneous mixture
Solvent – generally the larger component of the solution
Determines the physical state of the solution
Solute – generally the smaller component of the solution
Solute is dispersed in the solvent

3. Solution Composition
Concentrated solution – relatively large amount of solute
Dilute solution – relatively small amount of solute

4. Solution Composition
Unsaturated solution –solution with less than the maximum amount of solute that will normally dissolve at a given temperature
Saturated solution - solution with maximum amount of solute that will normally dissolve at a given temperature

5. Solution Composition
Super-saturated solution - solution with more than the maximum amount of solute that will normally dissolve at a given temperature

6. Concentration Units Molarity (M) = moles solute/Liters solution
Molality (m) = moles solute/kg solvent
Mass % = Mass solute/mass solution x100%
Mole fraction (cA) = moles A/total moles

7. Normality Normality (N) = # gram equivalent wt./L solution
Gew = mass of an acid or base that produces 1 mole of H+ or OH -1
Normality = Molarity x (# H+ or OH -1 /mol)
1 M HCl = 1 N HCl
1 M H2SO4 = 2 N H2SO4
For acid base titrations:
(NAcid) (VAcid) = (NBase) (VBase)

8. Practice! Start by writing definitions for the concentration units M =
Mass % =
Mole fraction =

9. Starting with Molarity
Solution:
3.75 M H2SO4 solution with a density of 1.23 g/mL
Calculate:
Mass %
Molality
mole fraction of H2SO4

10. Starting with Masses Solution: Calculate:
A solution is made by combining 66.0 grams of acetone (C3H6 O) with grams of water.
Solution has a density of g/mL
Calculate:
Molarity – need volume of solution
Mass %
Molality
Mole fraction of acetone

11. Starting with Mass % Solution: Calculate: 35.4 % H3PO4
Density of 1.20 g/mL
Calculate:
Molarity
Molality
Mole fraction of H3PO4

12. Starting with Molality
Solution:
2.50 m HCl solution
Density of 1.15 g/mL
Calculate:
Molarity – need _______
Mass %
Mole fraction of HCl

13. Solution Formation Formation of a solution involves 3 steps
Separate the solute particles
expand the solute
Separate the solvent particles
Expand the solvent
Form the solution
Solute and solvent interact

14. Solution Formation
Each step of solution formation involves energy and has a DH.
DH1 = energy needed to separate the solute
DH2 = energy needed to separate the solvent
DH3 = energy released when solution forms

15. Solution Formation DHsolution = DH1 + DH2 + DH3
Solutions form when the DHsolution is a small value – see page 504

16. Factors Impacting Solubility
Structure – like dissolves like
#44 on page 533

17. Factors Impacting Solubility
Pressure
Pressure has little impact on the solubility of liquids and solids
Pressure has a significant impact on the solubility of gases in a liquid
The higher the pressure of gaseous solute above a liquid the higher the concentration of the gas in the solution

18. Henry’s Law Henry’s Law: C = kP C = Concentration of dissolved gas
k = solution specific constant
P = partial P of the solute gas above
the solution
What does Henry’s Law mean?
No calculations required.
Page 506

19. Temperature and Solubility
Temperature has variable effects on the amount of solid that will dissolve in an aqueous solution!
See figure 11.6 page 508
Solutes will dissolve more rapidly at higher temperatures

20. Temperature and Solubility
The solubility of a gas in water decreases as temperature increases.
See figure 11.7 on page 508
Thermal pollution – read the story on page 510 when you get a chance

21. Vapor Pressure of Solutions
See Raoult’s Law on page 510
Psolution = csolvent P0 solvent

22. Colligative Properties
properties of a solution that depend upon the amount of dissolved solute, not the identity of the solute.
Freezing point depression
Boiling point elevation
Osmotic Pressure
Note: I will be weaving section 11.7 and the van’t Hoff factor (i) into my consideration of these properties and not consider it separately.

23. Colligative Properties
FP = Kf m i
BP = Kb m i
See page 517 for needed constants

24. Calculating the bp or fp of a solution
Calculating the molar mass of a solute from fp or bp data

25. Osmotic Pressure
Osmotic Pressure (P) is often used to determine the molar mass of large biological molecules
P = MRTi