44 0140 00 01 RPT Beers Law Colorimet

Beer’s Law & Colorimetry

Angela Carraway, Ph.D. and Peter Jeschofnig, Ph.D. Version 42-0140-00-01

Lab Report Assistant

This document is not meant to be a substitute for a formal laboratory report. The Lab Report Assistant is simply a summary of the experiment’s questions, diagrams if needed, and data tables that should be addressed in a formal lab report. The intent is to facilitate students’ writing of lab reports by providing this information in an editable file which can be sent to an instructor.

Exercise 1
Questions from Procedures

1. Convert %T to absorbance and prepare a Beer’s Law plot using this data.

Concentration of Various Samples
Sample Identification
Code
Concentration of M
(mol/L)

%T

A = 2 - log(%T)
Q5000
4.00 x 10-4
17.9

Q5001
3.20 x 10-4
25.0

Q5002
2.40 x 10-4
35.7

Q5003
1.60 x 10-4
50.2

Q5004
8.000 x 10-5
70.8

Questions from Procedures

3. What is the concentration of M in these samples?

Concentration of M
Sample Identification
Code

%T

A = 2 - log(%T)

A

M
Q021015-01
43.7
0.35951856
0.36
0.000192
Q021015-02
44.1
0.35556141
0.36

Q021015-03
43.8
0.35852589
0.36

Q021015-04
44.1
0.35556141
0.36

Q021015-05
43.8
0.35852589
0.36

4. What was their percent error?

5. Does Batch 021015 meet legal requirements?

Exercise 2
Observations

Data Table 1: Concentrations of Blue Dye

Well #

1

2

3

4

5

6

7

8

9

10

Drops of Blue Dye Solution

1

2

3

4

5

6

7

8

9

10

Drops of Distilled Water

9

8

7

6

5

4

3

2

1

0

Calculated Concentration

Exercise 3
Observations

(Only if colorimeter is used in this experiment.)

Data Table 2: Dilution
Test tube
Number

Solutions
Concentration
(M)
Concentration
(ppm)

3
Starting dilution (100 mL water and drops of blue#1 dye)

2
1:1 Dilution (1 part water - 1 part starting dye solution)

1
2:1 Dilution (2 parts water - 1 part starting dye solution)

0

Zero standard – distilled water

0

0

Data Table 3: Resistance vs. Concentration

Zero standard
2:1 standard
1:1 standard
Original
dilution
Commercial drink sample
Concentration (M)
0

Concentration (ppm)

Resistance, Ω

Resistance, Ω

Average Resistance, Ω

Exercise 3
Questions

Fully discuss answers to the following questions. Yes or No responses are not sufficient. A. Was your calibration curve as linear as you expected?

B. Did you experience any “drift” of the resistance readings?

C. What is the equation of your best-fit line?

D. What commercial drink did you analyze?

E. Assuming that the same commercial drink was analyzed in both colorimetry methods, how did the results compare?

F. Which technique should give more accurate results?

G. What are some of the potential sources for errors in this experiment