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Dakota state university page 204 of 232 experiment 20

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Unformatted text preview: onfident in your ability to make this transition, and will help you out in this endeavor. Once you realize that you can do this, you may well find that it is the single most important thing you can learn in college; how do I solve a problem that is beyond what we’ve done in a textbook? Towards this end, we will be providing you with a series of problems, and would like you to work with your lab partners to devise an approach to resolve each problem. We’ll start off with very straightforward problems, where the path is relatively clear, but as time goes on, you can expect less and less direction to foster creative independent thought. Unfortunately, regardless of how clever one is in experimental procedure, there is no meaning unless it is clear how to package and present the results. For this reason, we’ll have to begin with experiments that are easy to perform and see, but with a primary focus of searching a topics background and reporting results. This experiment represents a simple straightforward example of just such a project. It is not terribly challenging in and of itself, so it makes a convenient platform on which to build several new skills, such as: - Performing literature searches - Writing scientific papers - Analyzing data in a statistically relevant manner - Preparing scientific presentations - Giving scientific presentations -And using the PASCO system for data acquisition and analysis. As you perform this experiment, we will be giving you guidance on each of these topics, and although we expect good results from you, we will be giving primary focus to each of the aforementioned goals as the project proceeds, and would like you to focus on these points as the primary purpose of this experiment. Dakota State University page 204 of 232 Experiment 20: Beer’s Law General Chemistry I and II Lab Manual Experimental background: Believe it or not, you already have an inherent understanding of Beer’s law. If I were to give you two samples of water and ask you which has more iron contamination, you’d choose the darker one as the most likely suspect. Also, if I were to put the iron contaminated water in a large fish tank and ask you which direction would look darker, you’d say it would be darker looking from the side because the path is longer through the water. This is all Beer’s law says; the solution is darker if the concentration (amount of substance per unit volume of the solution) is higher and/or if the path length is longer. So, you might ask, why, then, isn’t the law named after me? Well, that’s a great question, and there are two answers. First, it’s a lot of fun watching a Board of Regents member turn blue with anger whenever they think we are teaching something, anything, that might possibly involve an alcoholic beverage. Secondly, and most importantly, because Beer was the first one to do a careful quantitative study of the relationship between absorption and concentration (whoever Beer was; I’ve checked several references, most of which referenced Beer’s law, but say nothing of Beer himself, or, herself, as the case may be). When we say quantitative, what we mean is the first study where great care was taken to accurately measure absorptivity and concentration for many substances and many concentrations in an effort to derive a general mathematical expression relating absorption and concentration. Absorption is just that; it’s the amount of li...
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