LAB - Flame Test
Introduction
Chemists began studying colored flames in the 18th century and soon used “flame tests" to distinguish between some
elements. They discovered that different elements burn with different colored flames. Although some of the flames you will
be seeing will appear similar in color, their light can be separated with a prism into distinctly different bands of colors on
the visible light spectrum. These bands of colors are called atomic line spectra, and they are UNIQUE to each element.
How does an electron move between energy levels?
When an atom is heated to high temperatures, some
of the electrons may absorb enough energy to allow
them to jump to a higher energy level or excited state.
This state is highly unstable so the electrons fall back
into the lower energy levels, but as they are falling
back, the energy that was absorbed is emitted in the
form of electromagnetic radiation or as we know it,
visible light. The color of this light can be used as a
way to identify the elements involved.
Only metals with loosely held electrons are excited in a flame of a burner. Thus, flame tests are useful in identifying
metallic ions. A number of common metal ions (Li+1, Na+1, K+1, Ca+2, Ba+2, Sr+2 and Cu+2) give a distinct color to a flame.
Therefore, flame tests are useful in determining the identity of an unknown metal. Compounds of these ions provide the
beautiful colors you see in fireworks displays.
In this experiment, you will be performing a flame test of 7 known metal ions in a solution. In addition, you will be given an
unknown metal that you must determine the identity of by comparing it to the other flames.
Objectives:
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To determine the color flame of 7 known metallic ions and the identity of an unknown metallic ion.
Materials:
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Goggles and apron
Bunsen burner
7 chemicals and an unknown solution
Wooden splints
Procedure:
You will be observing the colors of flames for 7 different elements. Each element is dissolved in a solution of its
chloride salt. There is a different solution at each lab station. You will rotate to each station to perform the flame test and
make observations of the colors. You will then be given an unknown and will determine what metal is present in the
unknown based on your data.
At each station you will burn ONE splint while holding the splint with crucible tongs. When you are done dispose
of the splint in the waste beaker. Wait until told to rotate stations. You will leave the Bunsen burner on while rotating, be
extremely careful when moving from station to station.
Name ________________________________________________ Date_________________________ Period _______
Group Member Names_____________________________________________________________________________
Data Table: Fill in the color that the element emitted below.
Ion Name
Color of Flame Observed
Ion Name
Lithium Ion
Sodium Ion
Potassium Ion
Calcium Ion
Strontium Ion
Barium Ion
Copper (II) Ion
Unknown
Color of Flame Observed
Post Lab Questions:
1. Based on your data table, what metal do you believe is in your unknown sample? _______________________
2. Based on the data from the lab, which metal(s) emits the most energy?
_______________________
3. Based on the data from the lab, which metal(s) has the longest wavelength?
_______________________
4. Does a flame test identify the metallic ion or the nonmetallic ion?
_______________________
5. A student recorded the following results when testing 3 unknowns. Identify them by referring to your data table.
a. Red -
_________________________
b. Green -
_________________________
c.
_________________________
Yellowish green -
6. From the information provided in the introduction and the class discussion, explain how a color is produced in a
flame when a chemical is heated. Be sure to discuss what is happening to the electrons in terms of energy and
energy levels. Use complete sentences.
__________________________________________________________________________________________
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Perform the following wavelength, frequency and energy calculations. Write out the equation for each problem and show
ALL work with units. Round answers to the correct number of significant figures and answers must have a unit.
7. If the frequency of a red spectrum line is at 1.60 x 1014 Hz, what is its wavelength?
#7 Answer:
8. If the frequency of a violet spectrum line is at 2.50 x 1014 Hz, what is its energy?
#8 Answer:
9. Orange light has a wavelength of 600 nanometers, what frequency does this correspond to?
#9 Answer:
10. Yellow light corresponds to 3.40 x 10-19J of energy, what wavelength does this correspond to?
#10 Answer:
11. You are being paid to make a firework that should start off blue, turn red, and finally orange. In order to create the
display wanted with the chemicals that you have chosen, which drawing represents the correct firing order?
(Assume the first chemical to be fired should be placed nearest the fuse end of the cylinder.)
A
NaCl
NaCl
CuSO4
CuSO4
Sr(NO3)2
Sr(NO3)2
Sr(NO3)2
KCl
NaCl
B
C