AP Chemistry
Name: ___________________________
Group Members:
___________________________
___________________________
___________________________
Flame Test
Purpose and Objectives
If an element can be placed in solution and that solution aspirated into a burning flame, the
element’s electrons will absorb energy. This process is sometimes called “exciting” the electrons. As
those electrons then return to their normal or “ground” state, the energy absorbed must be emitted
in the form of electromagnetic radiation.
Every element emits a characteristic wavelength of light energy during this process. If the
wavelength of electromagnetic radiation emitted falls within the range of visible light, it can be seen
as a characteristic color of light energy. Just as a fingerprint is unique to each person, the color of
light emitted after excitation of an element is unique to that element.
Only a few elements emit a characteristic light within the visible region of the spectrum. For most
elements the characteristic wavelength falls within the ultraviolet (UV) or infrared (IR) region of the
spectrum. Barium, calcium, lithium, potassium, copper, boron, sodium, and strontium are examples
of elements that display a characteristic light in the visible region of the spectrum. Salts of these ions
will be used in this demonstration.
This lab utilizes q-tips or wooden splints dipped with a solution of a variety of salts to produce a
brilliantly colored flame. When the solution is placed into the flame of a burner, a spectacular ball of
colored fire forms that is easily visible in even large classrooms.
Equipment
CaCl2 , NaCl, KCl, LiCl, BaCl2, CuCl, (or substituted compounds)
wooden splints, distilled water
AP Chemistry
Procedure
1. Repeat with each solution.
2. Prepare a beaker of water.
3. Obtain the vials with salt solutions. Lower the wooden splint into one of the samples. (If
using wooden splints, you will need to allow them to soak overnight.)
4. Light your Bunsen burner.
5. Lower the q-tip into one of the samples – (If using wooden splints, remove from solution).
Place it in the flame and observe the color.
6. Allow the splint to burn until the color disappears. Try not to get the salts on the Bunsen
burner. Immediately place the burned end of the splint into the beaker with tap water to put
it out.
7. Record the color of the flame in the data table below.
8. Repeat steps 5 - 7 for the remaining salts.
9. Clean up: place the used wooden splints in the solid waste container. Tightly screw the
caps on the salt samples and put them back in the designated bin. Rinse and dry the beakers
you used. Wash your hands.
AP Chemistry
Name: ___________________________
Group Members:
___________________________
___________________________
___________________________
FLAME TEST
LAB DATA SHEET
Data Table
Metal Ion
Symbol w/
Charge
Color of Flame
Wavelength (nm)
Wavelength (m)
Lithium
Sodium
Potassium
Calcium
Barium
Copper (I)
Color of
Light
Wavelength of Light
(nm)
Color of Light
Wavelength of Light
(nm)
Violet
410.
Yellow-green
565.
Blue
470.
Yellow
580.
Blue-green
490.
Orange
600.
Green
520.
Red
650.
AP Chemistry
Analysis Questions
(Show all work – don’t forget units!)
1. What is the relationship between frequency and wavelength?
2. For Li+, Na+, and K+:
a. calculate the frequency of emitted light
b. calculate the energy emitted with one photon in Joules
c. calculate the energy released when one mole of electrons returns to the ground state in kJ
mol–1.
3. Rank the Group 1A elements tested in order of increasing energy emission when 1 mole of
electrons returns to the ground state. Explain this pattern in terms of changes in energy levels.
4. An excited electron falls from n = 4 to n = 2.
a. Calculate the energy change in Joules associated with this transition.
b. What is the wavelength in nm of the emitted electromagnetic radiation? What color is it?
c. Calculate the energy change in kJ mol–1.
5. An excited electron falls from n = 3 to n = 1.
a. Calculate the change in energy in Joules associated with this transition.
b. What is the wavelength in nm of the emitted light? How is this different from the
electromagnetic radiation emitted in Question 5b? Could you detect this light with your
eyes?
c. Calculate the energy change in kJ when one mole of electrons moves from the third principal
energy level to the first principal energy level.
6. A certain line in the spectrum of Hydrogen is associated with the electronic transition from the
fifth energy (n = 5) level to the third energy level (n = 3).
a. In the electronic transition described above, does the atom emit or absorb energy? Justify
your answer.
b. Calculate the wavelength of the photon associated with this spectral line. Account for the
observation that the energy associated with the same electronic transition in the He+ ion is
greater than that associated with the corresponding transition in the H atom.
7. When a chloride solution of an element is vaporized in a flame, the color of the flame is violet.
What element could be in the solution?
Conclusion