# After this was done the percent of copper was then

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interpolated value and the amount of solution in the volumetric flask. After this was done, the percent of copper was then calculated by dividing the grams of copper by the mass of the penny; this was done for all 3 pennies separately. Following this the mean of the percent was calculated for and then the standard deviation was also calculated for. Results : The results show that the older the penny was, the more it weighs, and the more absorbent. This clearly shown in (Table 1). This data also showed that as the penny got dirtier and more oxidized, it became lighter. Penny number 3, while being the newest (minted in 2000) was the lightest and had the least absorbance. Penny number 1 was the heaviest, cleanest, and most absorbent penny that was used in this experiment. Penny Age Condition Wavelength Absorbanc e Weight 1 1993 Clean 610.00 nm 0.711 AU 2.546 g 2 1996 Semi-cloudy 610.00 nm 0.621 AU 2.517 g 3 2000 Dirty with some oxidation 610.00 nm 0.470 AU 2.483 g Table 1, Data of penny characteristics In (Table 2), the pennies are shown to have a very low percentage and grams of copper. Penny number 1 had the highest percentage of copper, 0.0243%, while Penny number 3 had the lowest with 0.061% copper. This also corresponded with the grams of copper in the pennies, as penny number 1 had 6.18e-3gCu, while penny number 3 had only 1.52e-3gCu. The mean of the 4
percent of copper was calculated to be 0.149% and a standard deviation was calculated to be 0.0911. Penny g Cu % Cu Mean of % Cu Standard Deviation T-Test 1 6.18e-3 g 0.243% 2 3.61e-3 g 0.144% 0.149% 0.0911 0.0235 > 0.226 3 1.52e-3 g 0.061% Table 2, Data of penny properties According to Figure 1 and Table 3, as the concentration increased, so did the absorption. The Values that were used for Figure 1 are demonstrated in Table 3. The correlation for the graph was calculated by liner fit to be 0.962. This value was then used to solve for the interpolation value. The observances of the standard solutions corresponded with the absorbance of each penny. As a result the, the standard solutions were used as a framework to show how concentrated each penny actually was. The penny with its absorbance closest to the absorbance of a standard solution, had a concentration that corresponded to the absorbance of that standard solution. Concentration Wavelength Absorbance Interpolation Value 1.0 g/L 610.00 nm 0.900 AU 1.02 0.8 g/L 610.00 nm 0.660 AU 0.773 0.6 g/L 610.00 nm 0.495 AU 0.602 0.4 g/L 610.00 nm 0.283 AU 0.381 0.2 g/L 610.00 nm 0.127 AU 0.219 Table 3, Data of standard solution properties 5
Figure 1, Plotted points of Absorbance vs. Concentration for the 5 standard solutions Discussion: The mandated maximum amount of copper in pennies was set at 2.5% by Congress, starting in 1982. This meant that pennies made before 1982, were minted from 95% Copper and 5% Zinc. However, current pennies are minted from 97.5% Zinc and 2.5% Copper. The
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