# To calculate average thickness of the copper coating

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To calculate average thickness of the copper coating, the mass of Cu in one penny is divided by the density of copper (8.96 gcm-3) to give the volume of Cu on the penny1. This volume is then divided by the surface area of the entire penny. According to the U.S. Mint, a penny has a 19.05 mm diameter and a 1.52 mm height2. olumeofCu.196 cmCu96 mmCuV: 8.96 gcm−30.1759 gCu= 031 cm31000 mm3= 13urfaceAreaFace1ace2andS= +F+burfaceArea2[π () ]9.05mm.52mmS= 219.05 mm2+ 1• π • 1urfaceArea61.01 mmS= 62verageThickness(mm)297 mmA=196 mm3661.01 mm2= .To calculate the thickness in terms of atoms of copper, the atomic radius of copper (1.35 x 10-8cm)3is used. 297 mm, 00, 00 atomsofCu.1 cm10 mm1 atomCu1.35 x10−8 cm= 2 20The penny used in this lab was from 2015. Since it was minted post-1982, it is expected that it be composed of ~2.5% copper by mass, with the remaining ~97.5% being zinc2. This amounts to approximately .0625 g Cu in a penny, a value smaller than g. Therefore, the calculated.17590value of copper shell thickness is going to be larger than the actual value.
Given the calculated mass of copper in the penny, and a total penny mass of 2.500g, it
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