Virtual lab: Beer's law [30 points; 2 points / question in purple]

 

This virtual laboratory activity is based on investigations 1 (Beer's lab) and 2 (calibration curve) in your AP chemistry lab manual and handout to the in-person lab. The purpose of this virtual lab activity is to learn about Beer's law, a calibration curve, to apply it to determine the concentration of KMnO4 in a simulation, and laboratory error analysis.

introduction:

question: 1. what is beer's law ?; video 1 (view ~ 2:15 - 3:45) or video 2 (~ 1:00 - 4:00) or website 1

experimental protocol; take brief notes

colorimeter calibration - video 3 (duration ~ 2:45)

dilution to generate data for calibration curve: video 2 (view ~ 4:00 - 7:30; pipets have 2 sets of numbers, where the zero is either at the top or bottom)

measure absorbance or % transmission of samples: video 2 (view ~ 7:30 - 10:30)

questions regarding experimental protocol

2. what is a blank ? what is the purpose of a blank ?

3. why fill the cuvette ~ 75% ? hint: potential consequence if fill cuvette << 75 % ?

4. why wipe the outside of the curvette ? consequence (be specific; value is higher ? lower ? than the true value ?) of not doing so on your results ?

5. fill-in data table for concentration in video 2 @ ~ 7:30; show your work

experimental data collection using virtual lab, where YOU design the lab, collect the data, and analyze the data (e.g. calculations ? graph ?) to address the following questions use the KMnO4 simulation. refer to your data to support your answer as appropriate.

6. what is the relationship between absorbance versus wavelength (include the color of the light) ? include a graph of your simulated data and values of other parameters in your experimental conditions.

7. relate the color of the simulated KMnO4 solution and the preceding relationship between the absorbance versus wavelength (i.e. color of light). basis / rationale ? (hint: is the color of the simulated KMnO4 due to the absorbance or transmission of various wavelengths of light)

8. what is the role of cell length on absorbance ? refer to experimental data and your answer to question 1

9. which wavelength of light should you use in your measurements ? basis / rationale ?

10. what is a complimentary color ? answer question 7 using the term "complimentary color"

11. describe the relationship between the absorbance versus concentration of KMnO4. include a graph and values of other parameters in your experiemental conditions. what is a calibration curve (or standard curve) ? what is it's use ?

12. what is the concentration of KMnO4 if it's absorbance was 0.5 based on your calibration curve ? basis / rationale ?

in answering each question, as appropriate, include the data & its description; include appropriate data analysis

supplemental questions: AP chem student lab manual (investigation 2; video (~ 6" duration) of lab)

13. in regards to figure 1 on p. 26, justify the validity of the equation associated with the figure using Beer's law

14. in regards to figure 1 on p. 26, if the concentration in the left test tube is 75 µM, then what is the concentration in the right test tube ? justify your answer and describe how this lab could be done without a colorimeter or spectrophotometer and its basis / rationale. what is the similarity / difference between a colorimeter versus spectrophotometer ?

15. solve the problem on p. 28; show your work

 

lab report format

use Word (or google doc) and Excel (or google sheets)

work in pair (or 3 students with prior teacher approval, since there might be an odd number of students in the class; attach a note stating that your group can have 3 students and you got prior teacher approval onto your lab report)