Colorimetery and Beer's Law

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Calculating the Efficiency of a Fabricator

Introduction. In this experiment the amount of copper in pennies was calculated in order to determine the efficiency of the fabricator in manufacturing the correct amounts of copper and zinc in pennies. The efficiency of the fabricator was calculated through the use of a colorimeter and Beer's Law. This experiment is important in order to find out if the fabricator process is losing money due to the fact that copper ($7.20/kg) costs more than nickel ($3.10/kg).

Experimental Procedure. A post-1982 penny was weighed. Approximately 15 mL of 10 HNO3 was placed into a beaker. The beaker was placed under the fume hood and the penny was added to the beaker of HNO3. During the reaction it was observed that the solution began to bubble, the solution turned green, white foam formed, copper smoke was emitted, and toward the end the solution began to turn blue. After the penny reaction reached completion when the penny fully dissolved, the solution was next diluted to 25.00 mL in a 25 mL volumetric flask. Four dilutions of the stock solution were made with the use of deionized water (0.0500 M, 0.100 M, 0.150 M, 0.200 M). Obtained 7 cuvettes and filled one with deionized water, one with the stock solution, and one with the penny solution. The other four were four cuvettes were filled with each dilution (0.0500 M, 0.100 M, 0.150 M, 0.200 M). The computer was set up and the absorbance of each of the solutions were measured by placing each cuvette in the colorimeter. The concentration was calculated using the colorimeter program on the computer.

Data/ Results. The results show that the experimental values were not equal to theoretical values. This result was reached by using the equation for Beer's law, A = Ɛlc. The equation allowed for the concentration of copper to be determined using stoichiometry and mass percent.


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