Chem 15 Lab 5 Formal writeup

Chem 15 Lab 5 Formal writeup - Tien Wei (Tom) Lee SID:...

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Tien Wei (Tom) Lee SID: 21846711 Chem 15 Lab Lab Section 101 GSI: Jamie Kulp Lab Partner: Yun Liang Experiment 5 Spectrophotometric analysis of mixtures: Simultaneous determination of two dyes in solution Abstract: Purpose: The purpose of this experiment is to use spectrophotometry to figure out the concentration of an unknown uncolored sample. Theory and Methods: The experimental technique used in this lab is called spectrophotometry, which uses light to measure the chemical concentrations. Students will use absorbance measured by the photometer at a given wavelength and the Beer’s law equation to calculate the concentrations of both the red dye and the yellow dye in the unknown orange solution. The Beer-Lambert Law states that the absorbance is directly proportional to the concentration of a solution (Potts). Using the relationship between the cell path length and the analyte concentration, the Beer’s law equation A = ε l c is generated (Blauch). Here, A is the absorbance of the sample solution, ε is the molar absorptivity, sometimes also called extinction coefficient, l is the path length of the sample cell, and c is the concentration of the sample solution. The instrument used is called a spectrophotometer. It produces light of selected wavelengths from the spectrograph. The intensity of the light beam is then measured by the photometer. Students will first measure the absorbance at certain wavelength for both the yellow dye and the red dye solutions using the spectrophotometer. They will select two particular wavelengths that produce the greatest accuracy. Then, they measure the
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absorbance spectra of each of each known solution and the unknown solution at both of the chosen wavelenths. Results: .Data of the standard curves - Wavelength: 414 nm - Wavelength: 501 nm Concentration (mg/L) Absorbance (Au) Red 50: 50 2.2209 Red 50: 25 1.1879 Red 50: 12.5 0.77585 Red 50: 6.25 0.57888 Red 50: 3.125 0.46143 Yellow 5: 50 0.058506 Yellow 5: 25 0.14992 Yellow 5: 12.5 0.0072818 Yellow 5: 6.25 -0.0070796 Yellow 5: 3.125 -0.0050006 -Unknown mixture (undiluted) Wavelength: 414 nm Wavelength: 501 nm Absorbance (Au) 0.8577 0.81738 Concentration (mg/L) Absorbance (Au) Red: 50 0.64385 Red: 25 0.30931 Red: 12.5 0.18871
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This note was uploaded on 02/11/2012 for the course CHEMISTRY 15 taught by Professor Bordel during the Fall '11 term at Berkeley.

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Chem 15 Lab 5 Formal writeup - Tien Wei (Tom) Lee SID:...

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