Chem Lab
Flame Tests
Wendy Brewer
Completed: 3-21-08
(Make-up Assignment)
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Abstract
To understand the electromagnetic spectrum produced by metals simply by rea ding text is unnecessarily ridiculous. This experiment will give to such tired readers and any other observer a display to help them better understand the spectrum in the most sensible and much more appealing way- visually. When done, the lab researcher will be able to distinguish the different qualities of colour within a flame for each solution- known or unknown. Each element will be induced into an excited state, via burner, and will emit this absorbed energy by colouring the flame with its own unique hue.
Introduction
The colour of a flame depends on both element and the energy change taking place. Theorist of the atom, Bohr, explained that atoms absorb energy, which in turn makes its electrons “jump” to the successive, higher energy level. When energy is released, these electrons “fall” to their original level. This difference in levels are called photons, whose singular energy is described by the equation E=hv, where h stands for Planck’s constant (he was another scientist) and v is the frequency of the radiation. We can see the result of this- light, if the wavelength of the photon is anywhere from 400 nm to 700 nm. All wavelengths of visible light can be found in white light. Atoms of a specific element will, if excited, have a unique wavelength- meaning a unique colour of flame. In turn, a coloured flame can be used to find the identity of the element, and vice versa. This is precisely what we will do, asking ourselves “What colours are characteristic of particular metallic ions in a flame test?”
Materials
Chemical splash goggles
Laboratory apron
Solutions of the following salts:
Barium Nitrate
Copper Nitrate
Strontium Nitrate
Lithium Nitrate
Potassium Nitrate
Sodium Chloride
Calcium Nitrate
Nichrome wire loop
Beaker, 50-mL
Hydrochloric acid, 6.0 M
Lab burner
One unknown solution
Procedure
1. Put on your goggles and apron.
2. Obtain a beaker with about 10 mL of 6.0 M Hydrochloric acid and a nichrome wire loop. Light the burner, and adjust the flame to low. USE CAUTION.
3. For each test, dip wire loop in one solution. Place the wire in the burner flame and observe. Record your observations on Data Table 1. Repeat this step until you have tested all seven solutions. Repeat also for Unknown solution but record observations in Data Table 2.
Results
Data Table 1
Salt Solution
Colour
Barium Nitrate
Greenish
Copper
Teal-Green
Lithium Nitrate
Deep Red
Potassium Nitrate
Pale Pink-Purple
Sodium Chloride
Yellowy-Orange
Calcium Nitrate
Sparkly Orange
Strontium Nitrate
Reddish
Data Table 2
Salt Solution
Colour
UNKNOWN solution
Light Yellow Green
Conclusion
In conclusion, during the lab procedures I found that Barium was the metallic ion present in the unknown solution, mainly because the colours both flames shown a similar, light green. What was basically done in this lab was an experiment in which I could discern the different hues of singular elements, as well as view the resulting rainbow effect of the electromagnetic spectrum firsthand when excited (a.k.a. lit on fire), by inducing the release of photons from an elevated energy level in each element-sample. These colorful flames I saw were the physical manifestation of this release, and each colour was the result of each element’s energy having a different wavelength. Therefore, for every wavelength, there is a different, unique hue.
(If you could, double space this? You can make it 10-font, though, please.)
Thank you Shane!
You're so goddamn cool!