# Penny Lab Report

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Penny Lab Report
CHM151LL Laboratory Report Form Fall 2011

Title: Project 5: SPECTROPHOTOMETRIC ANALYSIS OF A PENNY

Date Run: 04/03/2012
Date Submitted: 04/15/2012

Objectives: The purpose of this experiment is to use spectrophotometry to determine the percentage of copper in a copper-clad penny, and to determine the thickness of copper layer on the copper-clad penny.

Introduction: In the spectrophotometric analysis of a penny lab, we will be conducting three experiments. The purpose of the first experiment is to find the maximum absorbance on the spectrometer to obtain the optimum wavelength. Once we have gathered that information, we will use the results in the other two experiments. The purpose of
It is the linear relationship between absorbance and concentration of an absorber of electromagnetic radiation. The law states that there is a logarithmic dependence between the transmission of light through a substance and the product of the absorption coefficient of the substance, and the distance the light travels through the material. In simplest terms, Beer’s Law is a physical law stating that the quantity of light absorbed by a substance dissolved in a non-absorbing solvent is directly proportional to the concentration of the substance and the path length of the …show more content…
When you carefully added ammonia to your solutions containing copper, a light-blue precipitate formed initially that eventually disappeared as more ammonia was added. What do you think this precipitate was? Write an equation.
The ammonia molecules attach slowly, and in between each attachment, there is a chemical equilibrium. The more ammonia is added, the more complex is formed, as the equilibrium is pushed to the product side. The blue color is the result of the complex absorbing light in the visible light spectrum, and having a concentration high enough for the eyes to detect.

7. If the atomic radius of a copper atom is 1.28 x 10-8 cm, how many atoms thick is the copper coating on your penny? R = 1.28 x 10^-8 cm (2) = d = 2.56 x 10^-8 cm Thickness in atoms = 9.11 x 10^-4 cm/ 2.56 x 10^-8 = 35623.8 atoms

Error Analysis:
8. What assumptions were made in the experiment and in the calculations? We assumed that the reaction would go to completion and that we would get a close to accurate

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