Experiment No.
FLAME SPECTRA
OBJECTIVE:
To identify a metal by flame test.
Materials: Materials: Strontium chloride, Lithium chloride, Barium chloride,
Calcium chloride, Potassium chloride, Sodium chloride, and dilute
Hydrochloric acid
Apparatus: test tubes, alcohol lamp, nichrome wire, beaker
INTRODUCTION:
When an atom absorbs energy, an electron is displaced from lower to
higher quantum level. This is not the stable configuration for these atoms and
therefore the excited electrons return to their stable state called the ground state.
As the electrons return to their ground state, they emit radiant energy
corresponding to the energy difference between the excited state and the more
stable quantum level to which they return.
Some of these energy emissions occur in the visible portion of the
electromagnetic spectrum and can observed with the naked eye. To be certain of
this identification of the metal ion by this technique requires the use of an
instrument called spectrometer. However, many elements can be identified
usually by flame test. In this experiment, you will excite atoms in a nitrate salt
using an alcohol lamp to provide energy and observe the color emitted by
electrons when they return to their stable configuration.
PROCEDURE:
I. Flame Spectra
1. Obtain a clean 14 cm long nichrome wire. Wash it with distilled water,
then heat in the alcohol lamp.
2. Heat the wire until all colors except the color of the flame disappeared.
If any color persists, dip the wire in dilute hydrochloric acid solution
and repeat the procedure. Allow to cool and dip the still warm wire
into your sample. Place the wire in the flame.
3. Observe and record the color produced.
4. Repeat the procedure with each of the metals that have been provided.
Before dipping the nichrome wire in another solution, make sure that
it is free from other solution. This may be done by rinsing the wire
with distilled water and then with the dilute hydrochloric acid and
finally heating over the flame.
5. Record the flame color of each known metals.
II. Unknown Salts
Using the same procedure above, compare the flame color of each known
salts with that of the unknown and identify the metal contained in the unknown
solutions. Identify the unknown salts.
Questions:
1. What is the principle behind flame test?
2. Why does nichrome wire need to be rinsed every time it will be used in
another solution?
Report Sheet no. 6
Name __________________ SecCode _____ Group No. _____ Date________
Experiment No. 6
FLAME SPECTRA
Flame Test
Metal Chlorides Color of the Flame
Lithium chloride __________________
Potassium chloride __________________
Barium chloride __________________
Strontium chloride __________________
Sodium chloride __________________
Calcium chloride __________________
Unknown: __________________
