Lab 7 - Flame Test

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					Name___________________________________________Date________________Hour____________
                                                                                                Lab #
     Lab         Flame Test                                                                     Clean up Stamp




     7
Objectives
 To experiment with flame test on different salts.
 To predict the identity of an unknown metal ion from a flame test.
 To list the flame color of three Group 1, three Group 2, and one Transition Group metals.

Equipment
      Bunsen Burner and Tubing              Sparker                              test tube holder
      8 test tubes                          Q-tips (8)                           Crucible tongs

Materials
      0.5 M NaCl solution                   0.5 M NaNO3 solution                 0.5 M LiNO3 solution
      0.5 M KNO3 solution                   0.5 M Ca(NO3)2 solution              0.5 M Ba(NO3)2 solution
      0.5 M Sr(NO3)2 solution               0.5 M Cu(NO3)2 solution              Solid NaCl
      Unknown A                             Unknown B
Introduction
A number of common metal ions (Li1+, Na1+, K1+, Ca2+, Ba2+, Sr2+, and Cu2+) give a distinct color to a flame.
Therefore, a flame test is often used as a confirmatory test in identifying an unknown metal.

Compounds of these ions provide the beautiful colors in a fireworks display. When glass is melted in a Bunsen
burner flame, sodium ions color the flame. A copper wire inserted into the flame often results in a striking flame
color. While the light emitted from a few excited metals ions is beautiful, in the laboratory a simple flame test is
often very helpful in identifying an unknown metal ion.

In this experiment you will observe and record the flame colors of several metals of Group 1 and 2.


Procedures
1.    To obtain good results in this experiment, your test tubes must be exceptionally clean to avoid
      contamination. To clean the ten test tubes, a 6 M HCl solution can be used. (NOTE – HCl is dangerous, be
      very careful when working with HCl and always use goggles.) To clean the tubes place a few drops into
      each test tube and use a test tube brush to clean the test tubes. Then rinse the test tubes with lots of water.

2.    Transfer about 5 mL of each solution from your teacher to your clean test tubes

3.    Light your Bunsen burner and adjust it so that you have a bright blue flame.

4.    Using a clean Q-tip, dip it into the NaCl solution so that the end of the Q-tip is saturated with the solution.
      Hold the tip of the Q-tip into the hottest part of the burner flame. **NOTE** Do NOT catch the Q-tip
      on fire. Observe the color of the flame and record in Data Table 1. Repeat this process again with the
      same Q-tip in the NaCl solution to confirm your results.


                                                     Lab 7
5.   Get a new clean Q-tip and repeat step 4 for the other 6 solutions. Use a new, clean Q-tip for each solution.
     Each time record the color of the flame in Data Table 1.
6.   Place a few crystals of solid NaCl on your lab table. Dampen a Q-tip with water and pick up the solid
     sodium chloride. Hold the sodium chloride into the flame and record your observations in Data Table 1.
7.   From your instructor obtain an unknown solution. Test it in the flame as you did with the known solutions.
     Place your answers in Data Table 1.



                                                  Data Table 1
                       Solution                                                Color of Flame

 0.5 NaCl solution ……………………………………
 0.5 M Ba(NO3)2 solution ……………………………
 0.5 M LiNO3 solution ……………………………….
 0.5 M KNO3 solution ……………………………….
 0.5 M Ca(NO3)2 solution ………………………….
 0.5 M NaNO3 solution ………………………………
 0.5 M Sr(NO3)2 solution ……………………………
 0.5 M Cu(NO3)2 solution ……………………………
 Solid NaCl ………………………………………….

            Unknown                              Color(s) of flame                 Metal Ion(s) it contains



Questions
1.   Is flame coloration a test for the metallic ion or for the nitrate ion?

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2.   Why do dry sodium chloride, and the solutions of sodium nitrate and sodium chloride all impart the same
     color to the flame?

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3.   If milk was boiling on a gas stove and it boiled over, what color would you expect to see? Explain.
     ______________________________________________________________________________

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4.   Why do the chemicals have to be heated in the flame before the colored light is emitted?



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                                                     Lab 7
Lab 7

				
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