Honors Chemistry
Mr. Trubic
St. John’s College High School
Lab: Flame Tests for Metals
F LAME T ESTS
FOR
Name _________________________________
M ETALS
Date ________________
Lab Partner(s) _______________________________________________________________________
Purpose
To observe and identify metallic ions, using flame tests.
Background
Have you ever wondered why a candle flame is yellow? The characteristic yellow of a candle flame
comes from the glow of burning carbon fragments. The carbon fragments are produced by the
incomplete combustion reaction of the wick and candle wax. When elements, such as carbon, are heated
to high temperatures, some of their electrons are excited to higher energy levels. When these excited
electrons fall back to lower energy levels, they release excess energy in packages of light called photons,
or light quanta. The color of the emitted light depends on its energy. Blue light is more energetic than
red light, for example. When heated, each element emits a characteristic pattern of light energies, which
is useful for identifying the element. The characteristic colors of light produced when substances are
heated in the flame of a gas burner are the basis of flame tests for several elements.
In this experiment, you will perform flame tests in order to identify several metallic elements. When
you enter the lab, you will find various solutions in test tubes with wooden splints immersed in them.
Flame tests will be performed using a wire loop, followed by the same tests performed using a wooden
splint.
Materials (per group)
Solutions:
potassium nitrate, KNO3
calcium nitrate, Ca(NO3)2
strontium nitrate, Sr(NO3)2
lithium chloride, LiCl
copper(II) nitrate, Cu(NO3)2
sodium nitrate, NaNO3
barium nitrate, Ba(NO3)2
6 M hydrochloric acid, HCl
unknown salt
wire loop
wooden splints
bunsen burner
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Honors Chemistry
Mr. Trubic
St. John’s College High School
Lab: Flame Tests for Metals
Laboratory Safety
Notify your teacher of any spills immediately.
Caution: Hydrochloric acid (HCl) is corrosive. If hydrochloric acid comes in contact with your skin,
CALMLY go to the nearest sink and wash the area with soap & water. Continue to rinse the area with
water for an additional 2 to 3 minutes.
Caution: Do not taste any of the substances or touch them with your hands. If any of the solutions come
in contact with your skin, CALMLY go to the nearest sink and wash the area with soap & water.
Continue to rinse the area with water for an additional 2 to 3 minutes.
Caution: Do not at any time touch the end of the wire loop used in the flame tests. This wire gets
extremely hot.
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Honors Chemistry
Mr. Trubic
St. John’s College High School
Lab: Flame Tests for Metals
Procedure
As you perform the experiment, record your observations in the data table on page 4.
1. Dip the wire loop into the 6 M HCl and then heat it in the flame of a gas burner, as shown in the
figure, for approximately 3 to 5 seconds. DO NOT heat it to the point where the wire loops turns
orange.
Note: 6 M HCl means “six molar” HCl = 6 mol HCl per liter of solution.
2. Dip the clean wire loop into a metal salt solution and heat the wire loop in the burner flame, as
shown in the figure. Record the color of the flame, as well as any other information you feel is
relevant, in the data table. Test the remaining known samples, cleaning the wire loop, as described
in Step 1, before each new sample is tested. Record your observations.
3. Perform a flame test on your unknown salt, marked “ ? ”. Record your observations.
4. Repeat Steps 2−3 using the wooden splints instead of the wire loop. After the flame test, dip the tip
of the wooden splint in a beaker of water before disposing of it.
5. In an empty test tube, mix small amounts of the various salt solutions. You may mix anywhere
from 2 to 7 solutions at once. Using the mixture, perform a flame test (using both the wire loop and
a wooden splint) and record your observations. Rinse the test tube with distilled water and repeat
this step with at least 3 additional combinations of solutions. Record your observations.
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Honors Chemistry
Mr. Trubic
St. John’s College High School
Lab: Flame Tests for Metals
Observations
DATA TABLE
Ion
Observations
sodium, Na+
potassium, K+
calcium, Ca2+
barium, Ba2+
strontium, Sr2+
lithium, Li+
copper, Cu2+
unknown
mixtures
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Honors Chemistry
Mr. Trubic
St. John’s College High School
Lab: Flame Tests for Metals
Analysis and Conclusions
1. List the elements that produced the most easily identified colors.
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2. Which elements are least easily identified? Explain.
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3. Which element produces the most intense color?
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4. Is a flame test useful for detecting metal ions present in a mixture of metal ions? Explain based on
your results for Step 4.
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5. The energy of colored light increases in the order red, yellow, green, blue, violet. List the metallic
elements used in the flame tests in order of increasing energy of the light emitted.
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Honors Chemistry
Mr. Trubic
St. John’s College High School
Lab: Flame Tests for Metals
6. Which method produced more brilliant colors that were easier to identify, the use of the wire loop
or the wooden splints? Develop an explanation for your observations. DO NOT simply restate your
observations.
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7. Identify the ion present in the unknown solution. Justify your response. If you are unsure, explain
why.
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8. Using the Bohr model, account for your observations.
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