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Lab Report #6 - Calculating Percent Composition of Pennies...

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Calculating Percent Composition of Pennies Using Colorimetry Introduction. In this experiment the concentration of a post-1982 penny was measured to find if the fabricator that makes planchets for the U.S. Mint was putting the correct composition of copper and zinc into the pennies. The concentration was calculated by first dissolving a single penny, and then using colorimetry and a Beer’s Law plot on the diluted penny solution. From the measured concentrations, the composition of the penny was calculated. The effectiveness of the experiment was found using experimental error calculations. Experimental Procedure. A post-1982 penny was weighted and dissolved into 15 mL of a 10 M nitric acid solution. Then the solution was diluted to 25 mL in a flask. To the side, 25 mL of a 0.299 M copper stock solution and de-ionized water were used to make four diluted solutions: 0.0500 M, 0.100 M, 0.150 M, and 0.200 M. Using the rules of proper cuvette use, 7 cuvettes were each filled with a single solution of the stock solution, each of the four copper dilutions, deionized water, and the penny solution. The colorimeter was set to 635 nm, and the cuvette of deionized water was placed in the colorimeter in order to calibrate the colorimeter. The standard solution cuvettes was then placed one-by-one into the colorimeter, and the data was collected on the computer chart in order to create a Beer’s Law plot. Finally, the penny solution was placed into the
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