Introduction:
In this lab, we sought to determine the identity of 10 unknown solutions by using the flame test. We burned the 10 unknown solutions using a Bunsen burner and an iron wire and observed the various colors of light produced.
Alexander Krzyston FT Alexander J Krzyston FT Alex James Krzyston
Alex Krzyston FT Alex J Krzyston FT Alexander James Krzyston
NORTHWESTERN UNIVERSITY FT EVANSTON FT BURR RIDGE
Different chemical produce different colors of light when burned because they have different energy levels (as a result of having different amounts of electrons). By known which chemical produce which colors of light we could determine the identities of the 10 solutions.
Overview:
The biggest challenge in this lab was differentiating become the colors. Deciding upon what color flame was produced by the different ions was very subject especially when trying to differentiate between the various colors of red and orange, between blue and green, and between pale blue and bluish white. Some of the solutions produced colors so similar we had to guess which ions were present. This was especially problematic with solution #1 and solution #8, both of which produced an orange yellow flame. Another issue we encountered with trying to determine the flame color was the fact that the iron wire loop we were using to burn the solution would start to turn orange when heated and alter the color of the flame. In addition, because the iron wire loops were had been frequently used before, there was residue left behind which would also alter the flame color. As a result, we had to guess which ions were present in a few of the solution.
An alteration to this lab which I think would be helpful in determine which ions were present in which solutions would be if when were given 10 solution in which the ions present were given. This way would could compare between the known and unknown solutions which would be help to determine what the colors produced by the ions looked like we burned. (This would prevent error due to the subjecting of differentiating between red and red orange and yellow is very subjective.)
Data/Observations:
Solution Flame Color and Intensity
1 Yellow, fairly intense
2 Pale blue/green intense
3 White Fairly intense
4 Red-orange Intense and persistent
5 Red Very intense and bright
6 Green Very intense
7 Yellow/green Pale
8 Yellow Intense
9 Pale purple almost white Not intense
10 Red intense
Results:
solution Identity of Ions
1 Na
2 Pb
3 Sb or As
4 Ca
5 Li
6 Cu
7 Ba
8 Na
9 K
10 Sr
A. Colored light is emitted as a result of burning the solutions because the electrons in the solution absorb energy in the form of heat from the flame and they are they are excited causing them to jump to the next energy level. When the electrons fall back to their ground state they emit energy in the form of light. Because different chemicals have different energy levels, they require different amounts of energy to be excited. As a result, they emit different colors of light when the electrons fall back to their ground state. (the different energy levels are a result of chemicals having different amounts of electrons)
The purpose of the cobalt blue glass is to eliminate the sodium effect. Sodium in flame produces a strong yellow light that empowers the weaker light produced by other metal ions. The cobalt blue glass absorbs the yellow light but allows other colors to pass through.
B. The flame test cannot be used to determine the identity of unknown mixtures of solution because the color produced by heating the solution would be a mixture/combination of the two colors. For instance if a solution contained Na and Pb, the resulting color of light would be green and one might confuse the solution of Na and Pb for one of Cu. In addition, some chemicals produce the same color light such as Sb and As which makes in difficult to differentiate between the two. Other chemicals produce weak colors that are difficult to see.
C. The electrons are excited by the heat from the flame, meaning that they are absorbing energy in the form of heat which raises them to the next energy level.
D. The chemicals need to be burned to get color in the flame because if they were just heated and not burned, they would not absorb enough energy to jump to the next energy level.
Additional Analysis:
i. Ions highest to lowest energy
K, As, Sb, Pb, Cu, Ba, Na, Ca, Sr, Li
ii. Ions highest to lowest frequenc
K, As, Sb, Pb, Cu, Ba, Na, Ca, Sr, Li
iii. Ions shortest to longest wavelength
K, As, Sb, Pb, Cu, Ba, Na, Ca, Sr, Li
iv. The relationship between energy, wavelength, and frequency is that as energy increase frequency increases and wavelength decreases. This is seen in our results; the elements with the highest energy also had the highest frequencies, but had the shortest wavelengths.
Overview:
The biggest challenge in this lab was differentiating become the colors. Deciding upon what color flame was produced by the different ions was very subject especially when trying to differentiate between the various colors of red and orange, between blue and green, and between pale blue and bluish white. Some of the solutions produced colors so similar we had to guess which ions were present. This was especially problematic with solution #1 and solution #8, both of which produced an orange yellow flame. Another issue we encountered with trying to determine the flame color was the fact that the iron wire loop we were using to burn the solution would start to turn orange when heated and alter the color of the flame. In addition, because the iron wire loops were had been frequently used before, there was residue left behind which would also alter the flame color. As a result, we had to guess which ions were present in a few of the solution.
An alteration to this lab which I think would be helpful in determine which ions were present in which solutions would be if when were given 10 solution in which the ions present were given. This way would could compare between the known and unknown solutions which would be help to determine what the colors produced by the ions looked like we burned. (This would prevent error due to the subjecting of differentiating between red and red orange and yellow is very subjective.)
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