This is a lab report template for the %Cu in brass lab.
I. Fill in the “Lab Report Title”
II. Fill in the “Research Question”
III. Fill in the “Background Paragraph” – research the use of the Beer’s Law graph and how it is
to be used in this lab.
IV. Pre-Lab
a. Describe the procedure used to collect data for the pre-lab simulation
b. Prepare a graph of the data collected in this section. Embed this graph within your lab report
HERE:
c. Answer the following questions:
1. Look at the different plots for the six different salts. Can you identify the chemical
species doing the absorbing (the metal ion, the polyatomic anion, or both).
2. Based on visual examination of the salt solutions, which were clear and which had a
color? How does this seem to relate to plots for the different salt solutions.
3. Calculate the molar absorptivity constant of the copper (II) sulfate at 460 nm, 540 nm,
and at 600nm.
4. Why is a particular wavelength used when determining the absorption of a particular
chemical species? Is it important to measure absorbance for all wavelengths from 400–
700 nm?
5. If the molar absorptivity of copper (II) sulfate at 630 nm is known, explain how you
could determine a wavelength where the molar absorptivity is half of that simply by
examining the absorption spectrum.
6. Balance and record the redox reaction that will occur. The unbalanced half reactions
are:
Cu(s) → Cu2+(aq)
NO3-1(aq) → NO
7. In your own words, explain the relationship between concentration, absorbance, and
wavelength.
8. There are 4 problems described on Page 16 of the lab supplement. Respond to these
questions HERE:
9. Write your calculations and response HERE for Problem 1 on page 19 of the lab
supplement:
V. Investigation
In class, we divided the procedure into three sections: The pre-lab simulation, prepare and test
brass sample (procedure 1-3,8), prepare and test copper (II) nitrate standard solutions (procedure
4-9,10). In part IV of this lab, you described the pre-lab, please follow the directions for
describing the lab procedure:
a. Prepare and test brass sample:
1. Describe the procedure used to prepare and collect data for the brass sample.
2. Find the mass of the brass sample used for your group and show the calculations used to
determine the amount of nitric acid needed to dissolve the brass sample.
3. What safety pre-cautions should be followed for this portion of the lab?
b. Prepare and test copper (II) nitrate standards solutions:
1. Describe the procedure used to prepare and collect data for the brass sample. Include the
calculations used to determine how to make the 0.200M, 0.100M, 0.050M, and 0.0250M
solutions.
2. Use the data for your assigned group to prepare the graph described in procedure step 8.
Embed this graph within your lab report HERE:
c. Data Evaluation and Calculations:
1. Describe how to determine [brass]. Based on this description, what is [brass] for your group?
2. Show calculations to determine the mass of copper dissolved in the brass solution.
3. Show calculations to determine the mass percent of copper in the brass sample.
VI. Conclusion Paragraph
Restate the original research question. Respond to the original research question and summarize
the methods used to respond to this research question.
VII. Extension
1. Why does the presence of zinc ions not interfere with the absorbance of the brass solution?
2. There is a problem described on Page 28 of the lab directions. Write your calculations and
response HERE: