Determining the Concentration of a solution: Beer's Law

Determining the Concentration of a solution: Beer's Law Objective In this lab of Determining the concentration of a unknown solution: Beers Law. We determined the concentration of a unknown CuSO4 solution by measuring its absorbance with the colorimeter. With all the calculations we were able to solve the linear regression Equation of absorbance vs. concentration and the alternate method. Materials

Vernier LabPro or CBL 2 interface .40 M CuSO4 solution Computer or handheld CuSO4 unknown solution Vernier Colorimeter Pipet pump or pump bulb one cuvette Distilled water five 20*150 mm test tubes test tube rack two 10 mL pipets or graduated cylinders stirring rod

two 100 mL beakers procedures 1. Obtain and wear goggles. 2. Obtain small volumes of 0.40 M CuSO4 solution and distilled water in separate beakers. 3. Label four clean, dry, test tubes 1–4. Use pipets to prepare five standard solutions according to the chart below. Thoroughly mix each solution with a stirring rod. Clean and dry the stirring rod between uses. Trail number

0.40 M CuSo4 (mL) Distilled H2O (mL) Concentration (M) 1 2 8 0.08 2 4 6 0.16 3 6 4 0.24 4 8 2 0.32 5 10 0 0.40

4.Set up the data collection system. Connect the LabPro or CBL 2 interface to the computer or handheld with the proper cable. a) Connect a colorimeter to channel 1 of the interface b) Start the data collection program. Be sure the program shows correct reading for the colorimeter. c) Set up data collection for events with entry. d) Follow the appropriate steps to calibrate the colorimeter.

5. Collect and record the absorbance values for each of the five standards solutions. Print a graph of absorbance vs. concentration.

6.Collect and record the absorbance value for the unknown solution that you have been assigned.

7. discard the solutions as directed by your instructor

Observation Trail Concentration (mol/L) Absorbance 1 0.080 .541 2 0.16 .845 3 0.24 1.057 4 0.32 1.206 5 0.40 1.31 6 Unknown number_ .967 In this observation as we placed more distilled water the absorbance was lower. We would rinse the cuvette with the next test tube that we were going to check the absorbance because there was ions and the more concentrated the cuvette was the reading or results wouldn't be as good. This was a indirect relationship the more ions that were left over the transmittance wouldn't be able to read through


1.Calculate the linear regression (best-fit line) equation of absorbance vs. concentration for the five standard CuSO4 solutions. Print sketch a graph showing the data and linear-regression equation for the standard solutions

2.Determine the concentration of the unknown CuSO4 solution. Explain how you made this determination.

3.Describe and alternate method for determining the molar concentration of your unknown sample of copper(2) sulfate solution using the standard data.

Conclusion In this lab I noticed the more CuSO4 ml you put in the testube and the less distilled water you put in the higher the concentration was. We came pretty close to the professors results and we didn't push enter the first trail we did so we had to start all over because otherwise our results would not be as accrued.