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# Beer's Law Lab - Light Absorption of Colored Solutions

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Procedure 1
Part I: Light Absorption of Colored Solutions:
1.Take three cuvettes from the Glassware shelf and place it on the workbench.

2. Fill the first cuvette with 4mL of 0.24M CuSO4 solution, the second cuvette with 4 mL of 0.1 M CoCl2 solution and the third one with 4 mL of 1M HNO3 from the Chemicals shelf.

3. Take a spectrophotometer from the Tools shelf and place it on the workbench.

4. Open the Properties window and focus it on the Spectrophotometer. Set the wavelength to 420 nm.

5. Drag the Spectrophotometer and drop it on the cuvette containing the nitric acid. This is your blank solution, set the wavelength to 400nm and click on the set absorbance to zero button found in the Properties window.

Remove the cuvette from the Spectrophotometer.

6. Drag and Drop the Spectrophotometer onto the cuvette with the copper solution. Record the absorbance for the copper solution.

7. Click on the spectrophotometer, and in the Properties window, increase the wavelength 20nm. Record the absorbance of the copper solution at this wavelength.

8. Continue increasing the wavelength by 20 nm and recording the absorbance of the solution up to a wavelength of 720 nm.

Remove the cuvette from the spectrophotometer.

9. Set the wavelength of the spectrophotometer back to 400 nm

10. Drag and drop the spectrophotometer onto the cuvette with the cobalt solution. Record the absorbance for this solution.

11. Increase the spectrophotometer wavelength by increments of 20 nm and record the absorbance of the cobalt solution at each wavelenght up to 720 nm. Repeat steps 5-8 and record absorbance readings for both solutions at 20 nm increments from wavelength of 400 nm to 720 nm.

Remove the cuvette from the spectrophotometer.

Nitric Acid at 420 - .01 (blank solution)

Copper solution at 400 - .01
420 - .01
440 - .01
460 - .02
480 - .02
500 - .02
520 - .02
540 - .02
560 - .02
580 - .03
600 - .53
620 - .63
640 - .74
660 - .84
680 - .95
700 - 1.06
At 720 - 1.19

Cobalt solution at 400 - .01
420 - .41
440 - .27
460 - .29
480 - .64
500 - .91
520 - .88
540 - .54
560 - .28
580 - .14
600 - .01
620 - .01
640 - .01
660 - .01
680 - .01
700 - .01
At 720 - .01

Assignment 1:
1. Make a plot of absorbance readings for each of the solutions vs. wavelength.
(how can I create a plot, using what technology and if I do this right will it be a linear equation?)

2. Connect the data points to create a smooth curve curve in order to depict the ABSORPTION SPECTRA of CuSO4 and CoCl2 respectively.

Procedure 2
Part II : Preparation of Copper Standard Solutions and Plotting the Calibration Curve.

You will be making a set of 3 standard solutions (known concentrations of (Cu²+) plus a blank solution (no Cu²+). The standard Cu²+ solutions will each contain a different amount of Cu²+ stock solution.

1. Take four test tubes from the Glassware shelf and place them on the workbench.

2. To prepare the blank solution, add 10 mL of 1.0 M HNO3 solution from the Chemicals shelf to the first test tube. This is your reference standard for standardizing light control.

Prepare the three solutions of known concentration

3. Add 6.0 mL of 1.0 M HNO3 and 4.0 mL of 0.24 M CuSO4 solutions from the Chemicals shelf to the second test tube.

4. Add 3.0 mL of 1.0 M HNO3 and 7.0 mL of 0.24 M CuSO4 solutions from the Chemicals shelf to the third test tube.

5. Add 10.0 mL of 0.24 M CuSO4 solution from the Chemicals shelf to the fourth test tube. Calculate the copper concentration of each solution you prepared.

6. Take four cuvettes from the Glassware shelf and place them on the workbench.

7. Fill each cuvette with 4 mL of solution from the test tubes respectively.

8. Take a spectrophotometer from the Tools shelf and drop it on the cuvette with the blank solution.

Calibrate the spectrophotometer

9. Open the Properties window, set the wavelength to 700 nm (that is the maximum wavelength at which copper is absorbed) and then click on the set absorbance to zero button to calibrate the spectrophotometer. Remove the cuvette from the spectrophotometer to the workbench.

10. Take the spectrophotometer from the workbench and drop it on the cuvette with the first solution. Measure the absorbance and then remove the cuvette from the spectrophotometer.

11. Drop the spectrophotometer onto the cuvette, read the absorbance and then remove the cuvette from the spectrophotometer.

12. Measure the absorbance of the final remaining solution you prepared and record the absorbance values.

Cuvette with first solution - .42 absorption
Cuvette with second solution - .74 absorption
Cuvette with third solution - 1.06 absoroption

Assignment 1 of Procedure 2:
1.Calculate the actual concentration of Cu²+ ion in your samples. Because you are simply diluting a copper containing solution of known concentration, you can use the equation

(conc. of original solution )*(volume of standard Cu²+)=(concentration of dilute solution)*(total solution volume)

(I don't even know where to begin with this one)

2. Make a plot of absorbance as a function of the copper (II) concentration (M) in each of the standards.

Procedure 3
Procedure Part III: Determine the Amount of Copper in a solutions of unknown copper concentration:

1.To prepare the unknown solutions, take three cuvettes from the Glassware shelf and place them on the workbench.

2. Add 4 mL of the unknown copper solution #1 from the Chemicals shelf to the first cuvette, and 4 mL of the unknown copper solution #2 from the Chemicals shelf to the second cuvette.

3. Add 4 mL of 1.0 M nitric acid from the chemicals shelf to the third cuvette. This is your blank solution.

4. Take a spectrophotometer from the workbench and drop it on the blank solution.

5. Open the Properties window of the spectrophotometer. Set the wavelength to the wavelength maximum as you determined from Procedure #1 and click on the 'set absorbance to zero' button. Remove the cuvette from the spectrophotometer.

6. To measure the unknown solutions you prepared, drop the spectrophotometer onto each cuvette, measure and record the absorbance of the solution and then remove the cuvette from the spectrophotometer.

Cuvette 1 - .04
Cuvette 2 - .4

Assignment 1 of Procedure 3
1. Determine the copper concentrations in your two unknown samples from the calibration plot. (Find the concentration that matches the measured absorbance of each sample.)

Record this information.

(I imagine this one should be easy once I figure out how to do the plot, so mainly I need help with #1 and #2)

Thank you.

https://brainmass.com/chemistry/beer-lambert-law/beers-law-lab-light-absorption-colored-solutions-424738

#### Solution Preview

Spectrophotometry / Beer's Law Lab/Assignment
Procedure 1
Part I: Light Absorption of Colored Solutions:
1.Take three cuvettes from the Glassware shelf and place it on the workbench.

2. Fill the first cuvette with 4mL of 0.24M CuSO4 solution, the second cuvette with 4 mL of 0.1 M CoCl2 solution and the third one with 4 mL of 1M HNO3 from the Chemicals shelf.

3. Take a spectrophotometer from the Tools shelf and place it on the workbench.

4. Open the Properties window and focus it on the Spectrophotometer. Set the wavelength to 420 nm.

5. Drag the Spectrophotometer and drop it on the cuvette containing the nitric acid. This is your blank solution, set the wavelength to 400nm and click on the set absorbance to zero button found in the Properties window.

Remove the cuvette from the Spectrophotometer.

6. Drag and Drop the Spectrophotometer onto the cuvette with the copper solution. Record the absorbance for the copper solution.

7. Click on the spectrophotometer, and in the Properties window, increase the wavelength 20nm. Record the absorbance of the copper solution at this wavelength.

8. Continue increasing the wavelength by 20 nm and recording the absorbance of the solution up to a wavelength of 720 nm.

Remove the cuvette from the spectrophotometer.

9. Set the wavelength of the spectrophotometer back to 400 nm

10. Drag and drop the spectrophotometer onto the cuvette with the cobalt solution. Record the absorbance for this solution.

11. Increase the spectrophotometer wavelength by increments of 20 nm and record the absorbance of the cobalt solution at each wavelenght up to 720 nm. Repeat steps 5-8 and record absorbance readings for both solutions at 20 nm increments from wavelength of 400 nm to 720 nm.

Remove the cuvette from the spectrophotometer.

Nitric Acid at 420 - .01 (blank solution)

Copper solution at 400 - .01
420 - .01
440 - .01
460 - .02
480 - .02
500 - .02
520 - .02
540 - .02
560 - .02
580 - .03
600 - .53
620 - .63
640 - .74
660 - .84
680 - .95
700 - 1.06
At 720 - 1.19

Cobalt solution at 400 - .01
420 - .41
440 - .27
460 - .29
480 - .64
500 - .91
520 - .88
540 - .54
560 - .28
580 - .14
600 - .01
620 - .01
640 - .01
660 - .01
680 - .01
700 - .01
At 720 - .01

Assignment 1:
1. Make a plot of absorbance readings for each of the solutions vs. wavelength.
(how can I create a plot, using what technology and if I do this right will it be a linear equation?)

2. Connect the data points to create a smooth curve in order to depict the ABSORPTION SPECTRA of CuSO4 and CoCl2 respectively.

Procedure 2
Part II : Preparation of Copper Standard Solutions and Plotting the Calibration Curve.

You will be ...

#### Solution Summary

A Beer's law lab for light absorption of colored solutions are examined.

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