Calculations

1. Determine the molarities of all the solutions in parts one, two, and three. Do

this by using M₁V₁ = M₂V₂

2. Make a calibration curve with a line of best fit. Make a scatter plot with

the absorbance values at λ_max on the y-axis and the concentrations on the x-

axis, using the data from parts 1 – 3. Use a spreadsheet program to draw a

line of best fit and display the equation for the line and the R² value on the

graph.

3. Determine the concentration of dye in the diluted unknown solution.

Use the absorbance value for the diluted unknown dye solution and the line of

best fit to determine this value.

4. Determine the concentration of dye in the original unknown solution.

Use the concentration of dye in the diluted unknown solution and the volumes

used in part 4 along with the dilution equation to make this determination.

Pre-Lab Questions

1. How are absorbance and the transmission of light through the sample related?

As the % transmission decreases, what happens to the absorbance?

2. What is the purpose of the blank in a UV-Vis absorption experiment?

3. Copper solutions have a blue appearance. At what wavelengths of light do you

expect a copper solution to show maximum absorbance?

4. A solution originally has a concentration of 1.3 x 10^-4 M. That solution is

diluted by taking 2.0 mL of it and diluting to a volume of 10.00 mL with a

volumetric flask. What is the concentration of the diluted solution?

5. Using the graph in figure 7, if a solution of the red form of orange carotenoid

protein measured an absorbance of 0.313 at 525 nm, what is the

concentration of the protein in the solution?

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