1. Properties of Solutions
Chapter 13

2. The Solution Process Section 13.1
A solution is formed when the solute becomes completely dispersed throughout the solvent
Solubility depends on two major factors:
Intermolecular forces
Natural tendency for objects to spread out as much as possible

3. Solvation of NaCl
The solvation process occurs when the intermolecular forces between solvent-solute are greater than that of solute-solute:

4. NaCl vs. Hexane
Why doesn’t NaCl dissolve in nonpolar solvents such as hexane, C6H14?

5. Energy Changes and Solution Formation
Hsoln = H1 + H2 + H3

6. Saturated Solutions and Solubility Section 13.2
A saturated solution exists in
a state of equilibrium between
solvated ions or molecules
and the crystallized form

7. Solubility
The solubility of a substance refers to the minimum amount of solute required to create a saturated solution at a given temperature
Ex: The solubility of NaCl in water is 35.7 g/ 100 mL of water at 0 ºC

8. Supersaturation
A supersaturated solution can be created under certain conditions
Contains more solute than required to make a saturated solution

9. Factors Affecting Solubility Section 13.3
The most common factors affecting solubility of compounds are:
Solute-Solvent interactions
Pressure Effects (Only for gases)
Temperature Effects

10. Solute-solvent Interactions
The stronger the intermolecular forces between solute and solvent (as opposed to solute-solute), the greater the solubility
Ex: NaCl/H2O vs. C6H12O6/H2O
I2/H2O vs. I2/Benzene
What intermolecular forces exist and which have the greatest magnitude?

11. Solutions of Liquids (Miscibility)
Essentially follows the rule that "like dissolves like"
Dipole-dipole interactions between solvent and solute determine the miscibility of liquids
butanol/H2O  soluble
diethyl ether/H2O  only slightly soluble

13. Pressure and Temperature Effects
The solubility of gases increases with increasing pressure
Explains "the bends" for SCUBA divers
Expressed mathematically via Henry's Law:
Solubility for all phases of matter increases with
increasing temperature

14. Expressing Concentration Section 13.4
Concentration is most frequently expressed as moles/L (M)
Other quantitative expressions:
mass %
ppm
ppb
mole fraction
molality (mol solute/kg solvent)

15. Mass Percentage & ppm Mass percent is always expressed as follows:
ppm is very similar to mass percent, sometimes expressed as mg/L:

16. Calculating Mass Percent
A chemical analysis shows that 25.0 g of a solution contains 2.00 g glucose. Calculate the concentration in mass percentage of glucose.
See Sample Exercise 13.4 (Pg. 542)

17. Molality Similar to molarity, but involves kg of solvent and not L
Typically only used when discussing colligative properties of solutions

18. Molality Calculations
Determine the molality of a solution that contains 5.00 g of NaCl dissolved in 200 g of water.
See Sample Exercise 13.5 (Pg. 544)

19. Conversion of Concentration Units
Ammonia is sold as a 24.5% aqueous solution. Express this concentration in both molality and mole fraction
See Sample Exercise 13.6 (Pg. 544)

20. Conversion of Concentration Units (cont.)
Determine the molarity of an aqueous HCl solution that is 2.00 molal. The density of this solution is g/mL.
See Sample Exercise 13.6 (Pg. 544)

21. Colligative Properties Section 13.5
Colligative properties of solutions include those properties that depend only on the quantity of solution and not what the solution is actually composed of
Ex: Lowering of vapor pressure, elevation of melting point, freezing point depression

22. Raoult's Law
Introduction of a nonvolatile solute to a volatile solvent always results in a lowering of the vapor pressure for the new system
Expressed as:

23. Solute Type
The type of solute that is used does not matter. It depends only on the total concentration of solute particles
Why does 1 mol NaCl lower the vapor pressure of water more than 1 mol of methanol (CH3OH)?

24. Raoult's Law Calculations
Cyclohexane (C6H12) has a vapor pressure of 99.0 torr at 25 ºC. What is the vapor pressure (in torr) of cyclohexane above a solution of 14.0 g napthalene (C10H8) in 50 g cyclohexane at 25 ºC?
See Sample Exercise 13.8 (Pg. 547)

25. Freezing Point Depression
For a pure liquid, intermolecular forces help align the molecules so that the phase change from liquid to solid can occur
Introduction of solute molecules disrupts this network and depresses the freezing point
This can be expressed mathematically as:

26. Freezing-Point Depression/Boiling-Point Elevation
The equations shown below takes into account the number of dissolved particles per mole:
The variable i is referred to as the van’t Hoff factor
Represents the number of particles
Remember colligative properties depend only on the quantity of dissolved particles not the type.

27. Calculation of Freezing-Point Depression
Pure ethylene freezes at 9.80 °C. A solution is made by dissolving g of ferrocene (molar mass = g/mol) in 10.0 g ethylene dibromide. The freezing-point depression constant, Kf for ethylene dibromide is 11.8 °C/molal. What is the freezing point of this solution?
See Sample Exercise 13.9 (Pg. 550)

28. Calculation of Boiling Point Elevation
A solution is prepared by dissolving 1.00 g of a nonvolatile solute in 15.0 g acetic acid. The boiling point of this solution is °C. The normal boiling point of acetic acid is °C and it's boiling point elevation constant is 3.07 °C/molal. What is the molar mass of the solute?
See Sample Exercise 13.9 (Pg. 550)

29. Freezing Point Depression in Aqueous Solutions
Arrange the following aqueous solutions in order of increasing freezing point: m sucrose, 0.02 m NaCl, 0.01 m CaCl2, 0.03 m HCl
See Sample Exercise (Pg. 551)

30. Osmotic Pressure
Osmotic pressure is a colligative property that only applies to the processes involving semipermeable membranes
Solvent always flows to the area with the least amount of solute particles
Osmotic pressure is commonly used to determine the molecular weight of large molecules (i.e. proteins or polymers)

31. Determination of Molar Mass via Osmotic Pressure
Hemoglobin is a large molecule that carries oxygen in human blood. A water solution that contains g of hemoglobin in 10.0 mL of solution has an osmotic pressure of 7.51 torr at 25 °C. What is the molar mass of hemoglobin?
See Sample Exercise (Pg. 556)