Full Lab Report
Callie Gray
Introduction:
In the flame test lab we undergo flame tests, a quick method of producing the characteristic colors of metallic ions. The loosely held electrons are easily excited in the flame and this energy emitted in the visible portion of the spectrum enables electrons to return to lower energy, producing a colored flame. This color is a combination of the wavelengths of each transition used to determine the identity of the ion. In the lab we are doing just this, testing different ions to see what color they produce. With the flame, the wire loop and our samples of ions, we should be able to identify each metallic ion by the emitted colors.
Pre-Lab Questions
1. Write out the electron configurations for each of the metallic ions to be tested in this investigation.
A) Ba2+ = Xe
=1s22s22p63s23p64s23d104p65s24d25p6
B) Cu2+ = Co
=1s22s22p63s23p64s233d7
C) Li+ = He
=1s2
D) K+ = Ar
=1s22s22p63s23p6
E) Sr2+ = Kr
=1s22s22p63s23p64s23d104p6
F) Ca2+ = Ar
=1s22s22p63s23p6
G) Na+ = Ne
=1s22s22p6
2. The flame tests indicate producing the characteristic colors of metallic ions. The color is a combination of the wavelengths of each transition and may be used to determine the identity of the ion
3. A metallic ion produces characteristic color in a flame test because the loosely held electrons of a metal are easily excited in the flame of a lab burner. The emission of energy in the visible portion of the spectrum as those electrons return to lower energy produces a colored flame.
4. Wavelengths that correspond to the visible spectrum are visible light. The color that has the shortest wavelength is cosmic rays. The color that has the longest wavelength is radio wave.
5. When handling 6.0 HCI you should wear your goggles and lab apron at all times.
6.It’s important to use a clean nichrom wire for each test because if you use a dirty wire you can contaminate your samples.
Materials:
– Chemical splash goggles
-Laboratory apron
-Latex gloves
-Well plate
-Marker pen
*Solutions of the following salts:
-Barium nitrate (Ba(NO3)2)
-Copper nitrate (Cu(NO3)2)
-Strontium nitrate (Sr(NO3)2)
-Lithium nitrate (LiNO3)
-Potassium nitrate (KNO3)
-Sodium chloride (NaCl)
-Calcium nitrate (Ca(NO3)2)
-Nichrome wire loop
-Beaker, 50-mL
-Hydrochloric acid, 6.0 M
-Lab burner
-Wash bottle with distilled water
-3 unknown solutions
Procedure:
1. Put on goggles and lab apron and secure any other safety precautions. Get a well plat and Label 7 wells with the given names of the known solutions. Put dropperful of each known solution into designated well.
2. Obtain latex gloves; retrieve a beaker filled with about 10 mL of 6.0 M HCI and a nichrome wire loop. Light the Bunsen burner and be sure to adjust the flame to low.
3. After moving on to each test, be sure that the nichrome wire is clean so you don’t contaminate the solutions. Clean the wire by rinsing it in distilled water using the wash bottle over the sink. Then dip it into the 6.0 M HCl Solution. Place in the flame for a few moments representing the control of the clean wire, you should see this after every trial.
4. *TEST SODIUM LAST as it has strong color which may affect other results. Dip the clean wire into one solution and place it in the burner flame and observe, record your observations in the data table 1. Clean the wire and repeat this step with the rest of the known solutions.
5. Obtain 3 unknown solutions from your teacher and repeat step 4 for each. Record observations in data table 2.
6. Turn off the Bunsen burner and clean up your work area, be sure to wash your hands before leaving.
Observations
DATA TABLE 1 FLAME TESTS OF KNOWN SOLUTIONS
Salt Solution Color
Barium Nit. (BA(NO3)2) yellow
Lithium Nit. (LiNO3) red
Strontium Nit (Sr(NO3)2) Red (lighter)
Potassium Nit. (KNO3) Purple
Copper Nit. (Cu(NO3)2) Green
Calcium Nit. (Ca(NO3)2) Pink
Sodium Chloride (NaCl) Orange
DATA TABLE 2 TESTS OF UNKNOWN SOLUTIONS
Unknown Color
A Red
B Red
C Pink
Analysis and Conclusion Questions:
1. The metallic ions present in the unknown solutions are Lithium in A and B and Calcium in C.
2. The color of each ion is the combination of the wavelengths in the transition. Barium nitrate and calcium nitrate both produce a pinkish color, and thus are some of the shorter wavelengths. Strontium nitrate produces a red color, while lithium nitrate puts off a red-orange color, thus also having the longest wavelengths. Copper (II) nitrate is a light violet, so it is one of the shorter wavelengths. Lastly is potassium nitrate, which puts off a yellow color, and lies in the middle of the visible spectrum, therefore, being a medium wavelength.
3. The visible spectrum ranges from red to indigo, covering the entire rainbow. Red is measured as the longest length at 700 nm, while pink is measured at the least at 400 nm. In between lie the green and blues, which lines are 500-600 nm in length.
Applications:
1. The yellow flame around the point of heating indicates that the solution is most likely potassium nitrate. The yellow flame also means that the wavelength is medium in length. It is observed when glass is heated because the electrons within the nitrate are excited and thus put off a yellow color.
2. The energy of a photon with the wavelength of 670.8 nm is about 1010 cm in wavelength size and puts off a dark red color.
3. If a burner were not available you could use another source of heat that produces a flame, but is safe.
4. Metallic salts are used in fireworks because the metallic salts are what give the fireworks incandescence and luminescence, therefore creating light from the heat and other sources.
Conclusion:
From this experiment I have learned that salt solutions containing strontium and lithium, both producing red, have longer wavelengths meanwhile salt solutions containing barium, calcium, and copper have shorter wavelengths. Practical problems that could have occurred during my experiment that could have affected my outcomes were contamination of the wire, in the future I will double check that I have thoroughly cleaned the wire, so not to cross contaminate any of the salt solutions.
Extra Credit:
1. Neon lights form different colors because even though the light is called neon, it is not always neon being used. Different colors besides red are created from different chemicals such as Mercury, along with the phosphor-coated tubes.
2. Kirchhoff and Bunsen discovered cesium and rubidium. When a material is heated to incandescence it emits light that is characteristic of the atomic makeup of the material. In the original spectroscope design in the early 19th cent., light entered a slit and a collimating lens transformed the light into a thin beam of parallel rays
