Lesson

Background

On a color wheel, red + yellow = orange and blue + yellow = green. In this lab, you will investigate whether this idea works when doing flame tests of metallic ions.

Purpose

Student will mix various metallic salts and then perform flame tests to determine if some dominant colors correspond to the reactivity of metals.

Safety

• Use caution around open flames.
• Wear protective gear when handling hot glassware.
• Always wear safety goggles when handling chemicals in the lab.
• Always be aware of an open flame. Do not reach over it, tie back hair, and secure lose clothing.

Materials

• The following solutions
  • 1.0-M NaCl
  • 1.0-M LiCl
  • 1.0-M KCl
  • 1.0-M SrCl₂
  • 1.0-M BaCl₂
  • 1.0-M CaCl₂
  • 1.0-M CuCl₂
• Wood splints
• Forceps
• Bunsen burner
• 22 small test tubes
• Test tube rack

Procedure

1. Place six small test tubes into a test tube rack.
2. To all six of the test tubes add 10 drops of NaCl solution.
3. To each of the test tubes holding the 10 drops of NaCl add:
   - 10 drops of LiCl to the first test tube and swirl to mix.
   - 10 drops of KCl to the second test tube and swirl to mix.
   - 10 drops of SrCl₂ to the third test tube and swirl to mix.
   - 10 drops of BaCl₂ to the fourth test tube and swirl to mix
   - 10 drops of CaCl₂ to the fifth test tube and swirl to mix
   - 10 drops of CuCl₂ to the sixth test tube and swirl to mix.
4. Break three wood splints in half and place one of the pieces into each of the six test tubes. Allow them to soak in the solution.
5. While the wood splints are soaking, five additional test tubes into the test tube rack and add 10 drops of LiCl to each of the five test tubes.
6. To each of the test tubes holding the 10 drops of LiCl add:
   - 10 drops of KCl to the first test tube and swirl to mix.
   - 10 drops of SrCl₂ to the second test tube and swirl to mix.
   - 10 drops of BaCl₂ to the third test tube and swirl to mix
   - 10 drops of CaCl₂ to the fourth test tube and swirl to mix
   - 10 drops of CuCl₂ to the fifth test tube and swirl to mix
7. Break three wood splints into half, and place one of the pieces into each of the five test tubes and allow them to soak in the solution.
8. Using the forceps, test each of the mixtures of sodium chloride by placing the wood splint into a Bunsen burner flame. Record the colors of the flame. Make sure to put only the wet portion of the wood splint into the flame.
9. Place four more test tubes in the rack and add 10 drops of KCl to each.
10. To each of the four test tubes holding the 10 drops of KCl add:
    - 10 drops of SrCl₂ to the first test tube and swirl to mix.
    - 10 drops of BaCl₂ to the second test tube and swirl to mix
    - 10 drops of CaCl₂ to the third test tube and swirl to mix
    - 10 drops of CuCl₂ to the fourth test tube and swirl to mix
11. Break two wood splints into half and place one of the pieces into each of the four test tubes holding the KCl. Allow them to soak into the solution.
12. Using the forceps, test each of the mixtures of lithium chloride by placing the wood splint into a Bunsen burner flame. Record the colors of the flame. Make sure to put only the wet portion of the wood splint into the flame.
13. Place three additional test tubes in the rack and add 10 drops of SrCl₂ to each of these.
14. To each of the three test tubes holding the 10 drops of SrCl₂ add:
    - 10 drops of BaCl₂ to the first test tube and swirl to mix
    - 10 drops of CaCl₂ to the second test tube and swirl to mix
    - 10 drops of CuCl₂ to the third test tube and swirl to mix
15. Break two wood splints into half and place one of the pieces into each of the four test tubes holding the SrCl₂. Allow them to soak into the solution.
16. Using the forceps, test each of the mixtures of potassium chloride by placing the wood splint into a Bunsen burner flame. Record the colors of the flame. Make sure to put only the wet portion of the wood splint into the flame.
17. Place two additional test tubes in the rack and add 10 drops of BaCl₂ to each of these.
18. To each of the two test tubes holding the 10 drops of BaCl₂ add:
    - 10 drops of CaCl₂ to the first test tube and swirl to mix
    - 10 drops of CuCl₂ to the second test tube and swirl to mix
19. Break a wood splint into half and place one of the pieces into each of the two test tubes holding the BaCl₂. Allow them to soak into the solution.
20. Place one more test tube in the rack and add 10 drops of CaCl₂ and 10 drops of CuCl₂. Swirl to mix. Add one of the left over wood splints and allow to soak.
21. Using the forceps, test each of the mixtures of strontium chloride by placing the wood splint into a Bunsen burner flame. Record the colors of the flame. Make sure to put only the wet portion of the wood splint into the flame.
22. Using the forceps, test each of the mixtures of barium chloride by placing the wood splint into a Bunsen burner flame. Record the colors of the flame. Make sure to put only the wet portion of the wood splint into the flame.
23. Using the forceps, test the mixtures of calcium chloride and copper(II) choride by placing the wood splint into a Bunsen burner flame. Record the colors of the flame. Make sure to put only the wet portion of the wood splint into the flame.
24. Place one last test tube in the test tube rack. To this test tube, add drops of each of the seven chemical solutions. Place a wood splint in the test tube and allow it to soak.
25. Before doing the flame test on the solution holding all of the metallic salts, predict what color you think the flame will be and why. After making your prediction, perform the flame test by putting the wood splint into the fire. Record the color of the flame.
26. When you have finished testing all of the solutions, dispose of the wood splints, pour any of the mixtures left in the test tube into the sink, rinsing with water, and wash the test tubes carefully.

Results/Observations

Prediction of Color of All Metallic Salts Mixed Together:

Analysis

1. In your testing, did any one color seem more predominant that others?

2. If a predominant color corresponds to higher reactivity, place the chemicals tested in order of reactivity. Check the activity series of metals and see if your order was correct.

1. ___________________________

2. ___________________________

3. ___________________________

4. ___________________________

5. ___________________________

6. ___________________________

7. ___________________________

3. Would flame testing be a good way to distinguish between mixtures of different chemicals? Explain.

Did any of the chemicals change their characteristic color found in regular flame when they were mixed with other chemicals? Explain your answer.