Lab 11
Flame Test Lab
Shiva Senthil
7/25/17
Introduction
The purpose of this lab was to observe how different atoms release different amounts of energy during chemical reactions. Nine known metallic ion solutions and two unknown solutions were heated to make the metal ions release energy and give off light.
Prelab Questions
1. What is the difference between ground state and an excited state?
The ground state is the lowest energy that an electron can have and excited state is when the electron has more energy than the ground state.
2. What does the word "emit" mean?
It means to "give off."
3. In this experiment, where are the atoms getting their excess energy from?
The atoms get energy from the heat from the flame.
4. Why do different atoms emit different colors of light?
Different atoms emit different colors of light because they release different amounts of energy during the reaction. The different energy levels mean different colors of light are emitted.
Data
Analysis Questions
2. What patterns do you notice in the groupings?
The color depends on the metal ion in the compound.
3. Predict the flame color for a substance called strontium sulfate.
The flame color would probably be red because the flame for strontium chloride was red.
4. What evidence do you have that atoms of certain elements produce flames of certain colors?
All of the compounds with the same metal burned at about the same color (e.g. all of the copper compounds burned green/green-blue, and both sodium compounds burned orange).
5. Can a flame test be used to identify a metal atom in a compound? Why or why not? What about a nonmetal atom?
Most of the time, a flame test can be used to identify the metal atom. This is because during a chemical reaction, the ion will always release the same color of light as the electron gains energy and moves closer to the electron. This is not true for a nonmetal ion because it is pushing the electron away from its nucleus, so it absorbs light rather than emitting it. Thus, nonmetal ions do not emit visible light and cannot be identified using a flame test.
6. Identify the two unknowns. What are they and how do you know?
Unknown 1 is a lithium compound and Unknown 2 is a potassium compound. The color of the flame in the first unknown was pink, the same as LiCl. The color of the flame in the second unknown was purple, the same as KCl. The nonmetal in the compounds cannot be identified, but the metals can.
7. What color flame would CuO produce?
Copper (II) oxide would produce a green or green-blue flame because all copper compounds produce the same colored flame. The three copper compounds in the lab all burned green or greenish blue.
2. What patterns do you notice in the groupings?
The color depends on the metal ion in the compound.
3. Predict the flame color for a substance called strontium sulfate.
The flame color would probably be red because the flame for strontium chloride was red.
4. What evidence do you have that atoms of certain elements produce flames of certain colors?
All of the compounds with the same metal burned at about the same color (e.g. all of the copper compounds burned green/green-blue, and both sodium compounds burned orange).
5. Can a flame test be used to identify a metal atom in a compound? Why or why not? What about a nonmetal atom?
Most of the time, a flame test can be used to identify the metal atom. This is because during a chemical reaction, the ion will always release the same color of light as the electron gains energy and moves closer to the electron. This is not true for a nonmetal ion because it is pushing the electron away from its nucleus, so it absorbs light rather than emitting it. Thus, nonmetal ions do not emit visible light and cannot be identified using a flame test.
6. Identify the two unknowns. What are they and how do you know?
Unknown 1 is a lithium compound and Unknown 2 is a potassium compound. The color of the flame in the first unknown was pink, the same as LiCl. The color of the flame in the second unknown was purple, the same as KCl. The nonmetal in the compounds cannot be identified, but the metals can.
7. What color flame would CuO produce?
Copper (II) oxide would produce a green or green-blue flame because all copper compounds produce the same colored flame. The three copper compounds in the lab all burned green or greenish blue.
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| The bright pink flame emitted when LiCl is heated. |
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