Teacher Notes – Flame Test Lab
Preparation:
Prepare 0.5 M stock solution of NaCl, KCl, LiCl, BaCl2, CuCl2, SrCl2, CaCl2
Select at least one of the solutions to prepare double the amount of stock. Label this solution(s)
“Unknown”.
*This test can be done using cotton Q-tips also. Heat the Q-tip until no color is imparted to the
flame. Recommend to the students that they try sodium last as it can overwhelm the other
colors. Wet the tip in water before dipping in the salt. Then introduce it to the flame.
Pre lab Exercise:
1. Why do we expect different metals to produce different color flames when burned?
Explanation of the Bohr model – different elements have did stable orbits around their
nuclei, this results in different wavelengths when electrons fall from higher energy orbits
to lower energy orbits.
2. The metal ions being tested are Na+, K+, Li+, Ba2+, Cu2+, Sr2+, and Ca2+. How many
electrons are in each ion?
Na – 10; K – 18; Li – 2; Ba – 2; Cu – 27; Sr – 36; Ca - 18
3. Classify the following processes as physical or chemical changes:
a. Dissolving the ionic compounds in water physical
b. Flame testing the solutions chemical
DATA TABLE
Metal
Flame Color
Na
Yellow
K
Pale purple
Li
Carmine red
Ba
Pale green
Cu
Green
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Sr
Crimson red
Ca
Brick red/red orange
Unknown
Analysis Questions
1. What is the identity of the metal in the unknown?
Various
2. Estimate the wavelength for each of the tested metal ions. Calculate the approximate
energy being emitted by each.
Na – about 3.4 x 10-19 J; K – about 5 x 10-19J; Li – about 3 x 10-19 J; Ba – about 3.5 x 1019
J; Cu – about 3.8 x 10-19 J; Sr – about 2.8 x 10-19 J; Ca – about 3.2 x 10-19 J
3. Some commercially available fireplace logs burn with a red and/or green flame. On the
basis of your data, what elements could be responsible for these colored flames?
Red – lithium; strontium; and calcium
Green – Barium; copper
4. Aerial fireworks contain gunpowder and chemicals that produce colors. What elements
would you include to produce the following colors?
a. Crimson red
Strontium
b. Yellow
Sodium
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Chemistry
Atomic Structure