Beer's Law Lab - Christina Wong AP Chemistry 4th Hour...

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Christina Wong AP Chemistry, 4 th Hour 12/19/2009 Determining Concentration: Beer’s Law Lab I. Purpose The purpose of this lab was to find the absorbance of five standard copper (II) sulfate solutions and then calculate the molar concentration of an unknown copper (II) sulfate solution after determining the absorbance with the colorimeter. II. Procedure We started by obtaining small volumes of 0.40 M CuSO 4 solution and distilled water in separate beakers, and prepared five standard solutions. Each solution had a different combination of milliliters of water and CuSO 4 , leading to different concentrations. We placed the first solution (then the rest of the solutions, each in their individual cuvettes) in an empty cuvette. We then set up a Logger Pro colorimeter, calibrated it, and collected the absorbance-concentration data for the five standard solutions using the colorimeter. Finally, we took an unknown CuSO 4 solution and used the colorimeter to determine its absorbance. The absorbencies were measured and points were plotted, and a line of best fir was produced on the graph. This graph helped determine the concentration of the unknown copper (II) sulfate solution after the unknown’s absorbance was found. III. Data Collection Trial Concentration (mol/L) Absorbance 1 0.080 0.065 2 0.16 0.168 3 0.24 0.254 4 0.32 0.369 5 0.40 0.432 6 Unknown number 2: 0.339 0.390 Cuvettes Colorimeter
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IV. Data Analysis 1. Calculate the linear regression equation of absorbance vs. concentration for the five standard CuSO 4 solutions. Print a graph showing the data and linear-regression equation for the standard solutions. *graph on separate page* y = 1.030x + 0.04155 (line of best fit, linear-regression equation) 2. Determine the concentration of the unknown CuSO 4 solution. Explain how you made this determination. Since the line of regression is y = 1.030x + 0.04155, with x being concentration and y being absorbance, the concentration can be solved of if the absorbance is known. The absorbance of the unknown solution was 0.390 by using the colorimeter. Since the absorbance is y, Approximate concentration: 0.390 = 1.030x + 0.04155
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This note was uploaded on 12/03/2011 for the course CHEM BIO P 101 taught by Professor Kk during the Spring '11 term at Rochester.

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Beer's Law Lab - Christina Wong AP Chemistry 4th Hour...

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