Chapter 3 Outline

1. Chemical Equations. Chemical equations are simply a shorthand notation for the recipe of a chemical reaction. They tell you what you start with, what you end with, how much you need, and how much you make. You start with the reactants (things on the left) and make the products (things on the right). The arrow in the middle tells you what way the reaction goes (for now it will always be left to right). The chemical equation tells you how everything is related in a chemical reaction. Understanding this is a key point in this class.

2. Balancing Chemical Equations. In a chemical reaction, molecular bonds are broken and created. Basically things are rearranged. It is critical that when you do this rearrangement, you don't leave anything out. That is what balancing equations is all about. If you don't balance your equations, all the mathematical problems that you work using the information in the chemical equation will be WRONG! This is another must learn point for the class. Be careful, take your time, and get enough practice that you ALWAYS get the right answer when balancing reactions. Always check to see that an equation is balanced. If you don't check, YOU WILL GET THE WRONG ANSWER!

3. Properties of Compounds in Aqueous Solution. This section explains what happens to ionic compounds in solution. The model shown in Figure 5.1 of an ionic compound dissolving is really important. Always keep in mind what happens when ionic compounds dissolve. For this semester we will stick with reactions of strong electrolytes, where things dissolve completely. The concept of a week electrolyte is also introduced, these are compounds that dissociate a little bit. This complicates what happens in solution and you will learn how to deal with these complications next semester. For now, you can assume that things are either strong electrolytes or nonelectrolytes. Figure 5.4 shows solubility rules for ionic compounds in water. If you know these rules, you can predict what will happen to an ionic compound in water. You can answer the question (will it dissolve). You MUST know this. If you do not, you will probably fail every exam this semester, and several next semester. So get out your notecards and get to work.

4. Precipitation Reactions. After you know the solubility rules, it will be easy to predict when a precipitation reaction will occur. The general setup is that you take two different soluble compounds and dissolve them seperately in water. These two solutions are then mixed together. IF there is a combination of ions that is insoluble in this new mixture, they will form a precipitate. These reactions can be written several different ways; the overall equation (where things are written as compounds), the ionic equation (where all ions are written as ions); and the net ionic equation (spectator ions that do not react are dropped from the ionic equation).

5. Acids and Bases. You will need to be able to identify and name acids. Memorize the strong acids listed in table 5.2. Recognize bases, usually metal hydroxides ammonium is the common exception.

6. Reactions of Acids and Bases. This is the next type of reaction, we will do LOTS of work with acid base reactions this year, so get to know what they are all about. There are several different "theories" of acid base reactions that explain what is happening. Writing out ionic equations will be very helpful for determining what will react. In general if an acid and a base react, they produce a salt and water.

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