Chapter 12 Outline

This chapter is about Solutions and Their Behavior. There are several basic concepts that are important and a couple of different mathematical relationships in this chapter. Because you should be very familiar with many of the characteristics of solutions, it is an easy chapter if you use some common sense. This chapter is also a nice example of how a model of what happens on the molecular level will help make sense of the macro scale behavior of a system. Take a close look at the video clips for this chapter and keep them in mind as you solve problems.

12.1 Thirsty Solutions: Why You Should Not Drink Seawater

12.2 Types of Solutions and Solubility

This section discusses the properties of liquids and shows how the intermolecular forces effect these properties. Understanding the strength of the intermolecular forces between: ions, permenant dipoles and induced dipoles is used to explain differences in these properties.
  1. Interactions between Ions and Molecules with a permenant dipole. Molecules like water have a permentant dipole - review what makes a molecule polar in chapter 8. These interactions are fairly strong.
  2. Interactions between molecules with a permenant dipole. Since a permenant dipole is not as charged as an ion, these interactions are a bit weaker.
  3. Hydrogen bonding. Since OH and NH bonds are fairly polar and H atoms are very small. Dipole interactions with these molecules are much stronger than other permenant dipole interactions. Since OH and NH bonds are very common in bological systems, these interactions are very important for biochemistry.
  4. Hydrongen Bonding and the unusual properties of water. Water has OH bonds and since water is so common so hydrogen bonding in water is important. It is used to explain a number of unusual properties of water.
  5. Dipole/Induced Dipole forces. A non-polar molecule may have a temporary dipole induced by a polar molecule. These induced dipoes are not as strong a charge as a polar molecule so these interactions are not very strong.
  6. London Disperison Forces: Induced Dipole/Induced Dipole forces. These interactions betweeen two temporary diples are very weak.

12.3 Energetics of Solution Formation

12.4 Solution Equilibrium and Factors Affecting Solubility

This section discusses what happens on a molecular level when something dissolves in a solution. Check out the video clips. Remember "like dissolves like". Understand what it means if a solution is saturated. Henry's law describes the solubility of a gas in a liquid.

12.5 Expressing Solution Concentration

Units of Concentration. Concentration units may be experessed a variety of different ways. The units used depend upon the application. You need to know the definitions for solvent, solute and solution in order to understand these problems. The abbreviations are important; M for molarity, m for molality, X for mole fraction, ppm for parts per million. Know each of the following:

12.6 Colligative Properties: Vapor Pressure Lowering, Freezing Point Depression, Boiling Point Elevation, and Osmotic Pressure

This section is the bulk of the chapter. Colligative properties are properties that depend only upon the concentration of the solute, not the identity of the solute. Colligative properties include vapor pressure (Raoult's law), boiling point elevation, freezing point depression and osmotic pressure. Understand the practical implications of these, look carefully at the figures and video clips to understand the molecular basis for this behavior, and be able to work problems.

12.7 Colligative Properties of Strong Electrolyte Solutions

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Scott Van Bramer
Department of Chemistry
Widener University
Chester, PA 19013

Please send any comments, corrections, or suggestions to svanbram@science.widener.edu.

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Last Updated Friday, May 25, 2001 2:11:17 PM