Analysis Of Copper In A Penny By Ultraviolet-Visible Spectroscopy

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Sarah Everett CHEM 316 Monday 12-3:50 February 15, 2017 Analysis of Copper in a Penny by Atomic Absorption Spectroscopy and Ultraviolet-Visible Spectroscopy Introduction: The United States cent coin, also known as the penny, was originally composed of pure copper from 1793 to 1837 and the composition of copper in the penny has been diminishing since. For the next 145 years, the penny’s copper composition wavered between 95% and 88% until 1982 where the copper composition was reduced to 2.5% while the rest of penny was composed of 97.5% zinc. The reason for this drastic change of copper composition is unknown. However, the use of copper extends further than just penny composition. Copper is quite useful in many realms, especially construction, since it is both water damage resistant and it can conduct electricity. Copper …show more content…

The first is atomic absorption (AA) spectroscopy which is a more sensitive tool of measurement in that it excites individual metal atoms. The second is ultraviolet-visible (UV-Vis) spectroscopy which is a less sensitive tool of measurement in that it excites the whole molecule or ion. Atomic spectroscopy is used for the measurement of metallic elements at major and trace levels. In AA spectroscopy, light of a specific frequency is passed through a flame containing free atoms. Absorbance of light is measured and is proportional to the concentration of atoms. In an atomic spectroscopy experiment, the liquid sample is sucked through a plastic tube into a flame whose high temperature will break molecules apart into atoms. The concentration of the element in the flame is measured by the absorption of light. From there, a monochromator selects the wavelength that will reach the detector. UV-Vis spectroscopy is used for quantitative determination of compounds that absorb UV radiation. This determination is based on Beer’s

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