FLAME TESTS FOR METALS

Background:  The active metals of groups 1 and 2 can be "excited" in a flame.  The energy (in the form of heat) in the flame causes the electrons in the metal to jump up into higher energy levels.  When the electrons fall from the excited state, they produce light.  Each metal produces a characteristic color of light.

Purpose:  To identify the presence of a metal found in each solution by observing the color produced when metal compounds are excited in a flame.  To determine the identity of a metal ion in an unknown solution.

Lab Safety:
** ALWAYS WEAR YOUR SAFETY GOGGLES! **
** TIE BACK LONG HAIR! **

Procedure:
1.  Rinse the nichrome wire in the beaker of water.

2.  Dip the nichrome wire found at your lab station into one of the solutions.  Place it into the flame as demonstrated by your instructor.  Carefully observe the color and record your observations.

3.  Use a beaker filled with water to rinse your wire again.  Now heat the wire and observe the color.  If the same color is produced as the last one you tested, rinse your wire again.  Repeat this process until there is no color change of the flame.

4.  Test the remainder of the solutions remembering to rinse the wire between solutions.

5.  Compare the known solutions with the unknown solution and record your observations.

6.  When you have finished the procedure, and tested all of the solutions, rinse and burn the wire one last time.

7.  Clean up your lab station as directed by your instructor.

Data:  Record the color of the flame for each of the known solutions.

Metal Ion

Color of Flame

Lithium

 

Sodium

 

Potassium

 

Calcium

 

Barium

 

Copper

 

 

 

 

 

Unknown # ____

 

Questions:
1.  What is the identity of the unknown based on your observations?  How did you know?

2.  According to the Bohr model of the atom, what happens in the atom that causes colors to be emitted during these
     flame tests?

3.  Why is it necessary to clean the wire before you test each solution?

4.  What do you think would happen if the unknown substance contained a mixture of two compounds?  Could each metal be identified?

5.  Understanding the flame test properties of the group 1 and 2 metals, what application could these chemicals be used for?

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