LAB- CHEMYSTERY CASE: SPARKY FIREWORKS
(Flame Tests)
Purpose:
To determine the contents of four unlabeled chemical containers by
performing flame tests to identify the metallic ions in each and then matching
them to the list of chemicals found on a shipping list.
CheMystery:
Sparky Fireworks Company has contacted you. They received by freight
train, a shipment of chemicals for use in their fireworks manufacturing plant.
Several of the boxcars had leaky roofs causing the labels to peel off the chemical
containers. Before the company can use the chemical compounds they must
match up the containers with the chemicals that were listed on the shipping
invoice. They have explained that the test for the presence of the metallic
elements in these compounds is to dip a nichrome wire into a solution of the
chemical and then place it in a Bunsen burner flame. Each metallic ion will turn
the flame a color characteristic of that metal. In this experiment you will identify
the contents of each container. The company has provided you with the
following materials:
1st- A nichrome wire wand.
2nd- Concentrated 12 M hydrochloric acid to clean the testing wand each time
a different solution is used.
3rd- Solutions of the chemicals found in the unlabeled containers. For
convenience they are labeled:
*Chemical #1, Chemical #2, chemical #3, and Chemical #4
th
4 - Solutions of the six chemicals listed below.
5th- A list of the six chemical compounds from the shipping invoice:
Barium Chloride
Calcium Nitrate
Copper Sulfate
Lithium Nitrate
Potassium Nitrate
Sodium Chloride
6th- Miscellaneous Lab Equipment: Safety goggles, apron, 10 mL beaker,
6- test tubes, test tube rack, test tube brush
* Each person does not get the same four chemicals.
Background:
When the electron(s) in an atom gain energy they move to a higher energy
level and the atom is said to be in the excited state. Atoms in the excited
state are unstable and as a result give off light energy as they return to
lower energy levels called the ground state. Different atoms give off
different colors of light. Some metallic ions may be excited by heating them
in a Bunsen burner flame. The color of light given off by the excited atoms is
then used to identify the metal. The following chart lists the characteristic
colors of several different metallic ions.
Chart #1: Accepted Flame Tests Results For Some Selected Metallic Ions
Metallic Ion
Lithium
Sodium
Potassium
Calcium
Barium
Copper
Accepted Flame
Color
Pinkish Red
Yellow
Violet
Yellowish Red
Yellowish Green
Emerald Green
Safety Caution:
1. Always wear goggles, an apron, and appropriate shoes while working
in the lab.
2. Assume all chemicals are toxic by ingestion and inhalation. Assume
they are skin and body irritants.
3. Hydrochloric acid is highly toxic by ingestion or inhalation and is
severely corrosive to the skin and eyes. Carefully put about 5 mL of
the acid in a 10 mL beaker to use to clean the testing wand.
4. Hot wands in cold liquid sizzle. Be careful! Put only the wire portion of
the testing wand into the solutions.
5. Open flames may ignite loose clothing or hair.
6. Hot objects may not appear to be hot.
Please Note:
When you begin this experiment, you will be testing the six known metallic
ions to see first hand their flame colors. You will check to make sure your
observations match those listed in the Chart #1: Accepted Flame Tests
Results For Some Selected Metallic Ions that is given to you on the previous
page. Then, you will test the four unknown chemicals to determine their identity.
Procedure:
Day #1
1. Obtain 6 test tubes and a test tube rack.
2. Rinse the test tubes at least three times each with tap water.
3. Label the test tubes one through six.
4. Pour/squirt/drop approximately four to five milliliters each of the six known
chemicals into the appropriately labeled test tubes. Please be sure that
you look at the Data Chart #1- Flame Test Results of Known
Substances shown below.
5. Drop/squirt about 5 mL of 12 M hydrochloric acid into a 10 mL beaker.
6. Using you flint striker light the Bunsen burner flame.
7. Take the nichrome wand and place the end with the nichrome wire into
the hydrochloric acid solution to ensure that the wand is clean. Then,
place the same end into the Bunsen burner flame. (Please note: If the tip
of the wand is hot, it will make a noise or sizzling sound when placed
into the beaker that has the HCl. Don’t jump, it will be o.k.!)
8. Repeat step #7 for a second time to ensure the tip of the wand is clean.
9. Take the tip of the nichrome wire wand and dip it into the Test Tube #1 that
contains barium chloride and place into the Bunsen burner flame. Then,
dip the wand back into Test Tube #1 to confirm your observation. Finally,
record your observation in the Data Chart #1- Flame Test Results of
Known Substances.
10. Repeat steps 7 & 8 in order to clean the wand.
11. Dip the wand into each of the remaining solutions contained in the labeled
test tubes and record your observations in Data Chart #1 shown below.
Repeat steps 9 & 10 for the remaining chemicals.
Data Chart #1- Flame Test Results of Known Substances
#
of
Test
Tube
1
2
3
4
5
6
Identity of Chemical
Compound
Metallic
Ion
Accepted
Flame
Color
Barium Chloride
Calcium Nitrate
Copper Sulfate
Lithium Nitrate
Potassium Nitrate
Sodium Chloride
Barium
Calcium
Copper
Lithium
Potassium
Sodium
Yellowish Green
Yellowish Red
Emerald Green
Pinkish Red
Violet
Yellow
Observed
Flame
Color
12. Discard all of the chemicals from the test tubes down the drain being sure to
flush with plenty of water.
13. Turn the water faucet at your lab station on and tell everyone at your station
to stand back while you dump the HCl down the drain.
14. Clean all laboratory equipment and return each item to the proper location.
15. Wipe down and dry your area at the lab station.
16. Go to the front of the laboratory and work on conclusion questions for the
remainder of the period.
Day #2
1.
2.
3.
4.
Obtain 4 test tubes and a test tube rack.
Rinse the test tubes at least three times each with tap water.
Label the test tubes one through four.
Give the four labeled test tubes in the test tube rack to your chemistry
instructor so the test tubes can be fixed for you with the unknown
solutions. Please be sure that you look at the Data Chart #2- Flame Test
Results For Unknown Chemicals shown below.
5. Drop/squirt about 5 mL of 12 M hydrochloric acid into a 10 mL beaker.
6. Using you flint striker light the Bunsen burner flame.
7. Take the nichrome wand and place the end with the nichrome wire into
the hydrochloric acid solution to ensure that the wand is clean. Then,
place the same end into the Bunsen burner flame. (Please note: If the tip
of the wand is hot, it will make a noise or sizzling sound when placed
into the beaker that has the HCl. Don’t jump, it will be o.k.!)
8. Repeat step #7 for a second time to ensure the tip of the wand is clean.
9. Take the tip of the nichrome wire wand and dip it into the Test Tube #1 that
contains your first unknown chemical and put it into the flame. Then, dip
the wand back into Test Tube #1 to confirm your observation. Finally,
record your observation in the Data Chart #2- Flame Test Results For
Unknown Chemicals.
10. Repeat steps 7 & 8 in order to clean the wand.
11. Dip the wand into each of the remaining solutions contained in the labeled
test tubes (#2, #3, & #4) and record your observations in Data Chart #2
shown below. As you test the remaining chemicals please be sure to
repeat steps 9 & 10 for the remaining chemicals.
Data Chart #1- Flame Test Results of Known Substances
#
of
Test
Tube
1
2
3
4
Observed Flame
Color
Metallic
Ion
Identity of Chemical
Compound
12. Discard all of the chemicals from the test tubes down the drain being
sure to flush with plenty of water.
13. Turn the water faucet at your lab station on and tell everyone at your
lab station to stand back while you dump the HCl down the drain.
14. Clean all laboratory equipment and return each item to the proper
location.
15. Wipe down and dry your area at the lab station.
16. Go to the front of the laboratory and work on conclusion questions for
the remainder of the period.
Conclusion Questions For Sparky Fireworks
1. What was the purpose of this lab? (Hint: Look at the first page of this lab.)
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2. In three of four sentences explain why you were able to do this in terms of
excited atoms. (Hint: See Background information to this lab.)
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3. Write about anything in the experiment that might have went wrong or
could have caused error in your results. Include at least 2 possible
sources of error.
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4. What happens to the potential energy of an atom when an electron moves
from its ground state to an excited state? ______________________
5. As an atom in the excited state returns to the ground state, the energy of
the atom _______________________.
6. During a flame test, ions of a specific metal are heated in the flame of a
Bunsen burner. A characteristic color of light is emitted by these ions
in the flame when the electrons ______________ energy as they move
to _____________ energy levels.
7. The diagram below represents the bright-line spectra of four elements and a
bright-line spectrum produced by a mixture of three of these elements.
Which element is not present in the mixture? _______________
8. What is a possible electron configuration for a bromine atom in the excited
state?
________________________
9. Below is a diagram of the nucleus of an atom and principle energy
levels. Please draw an arrow that is labeled “Energy is increasing” in the
appropriate direction regarding the energy of electrons in relationship to the
distance from the nucleus.