by Todd A. Carlson, Grand Valley State University, Allendale, MI 49401
Dilution calculations are common in all areas of chemistry, particularly biochemistry. They also prove to be particularly difficult for many students. You may find this worksheet helpful as you work through some of the problems you will be doing this semester. Consider the following samples problems:
The definition given in Rule 1 provides the basic equation for calculating concentration and the two variations used to calculate volume and amount.
OR 
This approach to dilution calculations is based on the fact that all problems are based on very simple fundamentals outlined in Rules 1 through 3 The difficulty lies in the organization of the problem. Rules 1 through 3 are applied using a dilution chart. The chart provides visual clues to help you organize the problem. The chart has three rows (one each for concentration, amount and volume) and a column for each different solution in the problem. In this example there are four solutions: the original solution, a sample of the original solution, the diluted solution, and a sample of the dilution. Identifying the different solutions that need to be analyzed is probably the most difficult but also the most important aspect of the problem. All of the values given in the problem are written in the appropriate box of the chart. The box for the desired answer should be highlighted. The initial dilution chart for the sample problem above is shown in Table 1. The three rules above are then applied as shown in the example shown below. Table 2 shows the completed dilution chart with arrows indicating the procession of steps.
This procedure may seem tedious at first. There are shortcut methods that will give the answer with less work. If you can get the right answer using a different approach, then this chart method may not be necessary for you. However, all solution to this problem will ultimately use the same calculations organized differently. With practice, many students find that they can do these types of problems without the chart as the concepts of dilution calculations become intuitive. You do not have to use this method. However, I have found that for many students, the primary obstacle in problem solving is organization. If you find yourself saying "I don't know where to begin" when solving problems, then this method may help.
A Step By Step Solution To The Sample Problem:




















Table 2: The completed chart for the sample problem. The arrows
indicate the progression of the calculation.



















