FLAME TEST LAB


Name: ______Date: ______

Period: ______

Lab: Flame Tests

Discussion: When electrons in the ground state are heated to high temperatures or have electric current run through them, some electrons may absorb enough energy to allow them to “jump” to higher energy levels. These excited state electrons are unstable and they will “fall” back to their normal positions of lower energy. As the electrons return to the ground state, the energy that was absorbed is emitted in the form of electromagnetic energy. Some of this energy may be in the form of visible light.

I. Objective: To observe the characteristic colors produced by certain metallic ions when vaporized

in a flame; and to identify an unknown metallic ion by means of its flame test.

II. Materials and Equipment:

1. Q-Tips 3. Portable burners

2. 7 metallic salts 4. Cups with water.

III. Safety: Goggles must be worn at all times, hair must be tied back, sleeves should be rolled up. Never taste, sniff or touch chemicals used in the lab. No food or drink is permitted in the lab. You must wash your hands before leaving the lab and observe proper safety precautions when using the portable burners.

IV. Procedure:

1.  Put on safety goggles.

2.  Fill a beaker half way with water to depose of used Q-Tips.

3.  Set up Portable Burner.

4.  Take a Q-Tip, Dip it in water and then in the metallic ion coating the Q-Tip with the powder. Put the Q-Tip in the flame and observe and record its color.

5.  Repeat for all 6 ions.

6.  When you have finished testing your seven metallic ion solutions, obtain a sample of an

unknown solution. Perform a flame test and identify the metallic ion present by the color

of the flame.

7.  Clean up your Lab bench and wash your hands.

Metallic Ion / Color in Flame
NaCl
KCl
LiCl
CaCl2
SrCl
CuCl2
BaCl
Unknown

Lab Questions/Assignment:

Define the following terms:

A: Electron

B: Ground state

C: Excited state

1) What is the unknown metallic ion?

2) Some commercial fireplace logs burn with a green flame. On the basis of your data, what element could be responsible for this colored flame?

3) Many street lights give off a yellow glow. What element do you think is in them based on your lab data?

4) Some fireworks contain gunpowder that produces bright colors. What element do you think would produce a crimson red firework?

5) Using an illustrated diagram and the modern atomic theory, explain how light is created:

FLAME TEST RESULTS

Red
Carmine to Magenta: Lithium compounds. Masked by barium or sodium.
Scarlet or Crimson: Strontium compounds. Masked by barium.
Red: Rubidium (unfiltered flame)
Yellow-Red: Calcium compounds. Masked by barium.

Yellow
Gold: Iron
Intense Yellow: Sodium compounds, even in trace amounts. A yellow flame is not indicative of sodium unless it persists and is not intensified by

addition of 1% NaCl to the dry compound.

White
Bright White: Magnesium
White-Green: Zinc

Green
Emerald: Copper compounds, other than halides. Thallium.
Bright Green: Boron
Blue-Green: Phosphates, when moistened with H2SO4or B2O3.
Faint Green: Antimony and NH4compounds.
Yellow-Green: Barium, manganese(II), molybdenum.

Blue
Azure: Lead, selenium, bismuth, cesium, copper(I), CuCl2and other copper compounds moistened with hydrochloric acid, indium, lead.
Light Blue: Arsenic and come of its compounds.
Greenish Blue: CuBr2, antimony

Purple
Violet: Potassium compounds other than borates, phosphates, and silicates. Masked by sodium or lithium.
Lilac to Purple-Red: Potassium, rubidium, and/or cesium in the presence of sodium when viewed through a blue glass.

Flame Test Colors

Symbol / Element / Color
As / Arsenic / Blue
B / Boron / Bright green
Ba / Barium / Pale/Yellowish Green
Ca / Calcium / Orange to red
Cs / Cesium / Blue
Cu(I / Copper(I) / Blue
Cu(II) / Copper(II) non-halide / Green
Cu(II) / Copper(II) halide / Blue-green
Fe / Iron / Gold
In / Indium / Blue
K / Potassium / Lilac to red
Li / Lithium / Magenta to carmine
Mg / Magnesium / Bright white
Mn(II) / Manganese(II) / Yellowish green
Mo / Molybdenum / Yellowish green
Na / Sodium / Intense yellow
P / Phosphorus / Pale bluish green
Pb / Lead / Blue
Rb / Rubidium / Red to purple-red
Sb / Antimony / Pale green
Se / Selenium / Azure blue
Sr / Strontium / Crimson
Te / Tellurium / Pale green
Tl / Thallium / Pure green
Zn / Zinc / Bluish green to whitish green

Limitations of the Flame Test

The test cannot detect low concentrations of most ions.

The brightness of the signal varies from one sample to another. For example, the yellow emission from sodium is much brighter than the red emission from the same amount of lithium.

Impurities or contaminants affect the test results. Sodium, in particular, is present in most compounds and will color the flame. Sometimes a blue glass is used to filter out the yellow of sodium.

The test cannot differentiate between all elements. Several metals produce the same flame color. Some compounds do not change the color of the flame at all.