Flame Tests Lab ­ Chas Andres

Purpose: The Purpose of the Lab is to determine the characteristic colors of certain metallic ions.

Procedure: A 96-well plate was obtained first, and a small amount of HCL was moved from the beaker and into one of the wells with an eyedropper. Then, an equally small amount of both Barium Nitrate and Copper (II) Nitrate were placed into separate wells with an eyedropper. Then, a small beaker of distilled water was obtained. To test the first solution, a Nichrome wire loop was first washed in distilled water, then placed in the HCL, and then placed over the flame of a Bunsen burner until the loop became red hot. Then, the loop was dipped into the first solution (Barium Nitrate), and placed over the flame once more. The flame over the loop would turn a distinct color, in this case a yellowish white, and burn for a few seconds. Then, the loop was cleaned by placing it first in the water, then into the Acid, and then over the flame once more. Every solution was tested at least three times to make sure that the correct color was observed. Then, this procedure would be repeated with all of the other solutions. Copper (II) Nitrate, Strontium nitrate, Lithium nitrate, Potassium nitrate, Calcium nitrate, and Sodium Chloride. Once these solutions were tested and the color recorded, the solution 'Unknown Solution C' was tested in the same manner, and recorded.

Data:

Table of the colors given off by the different ionic compounds

Barium nitrate ­ Yellowish White

Strontium nitrate ­ Reddish Orange

Copper (II) nitrate ­ Green

Potassium nitrate ­ Orange and pink with a little white

Lithium nitrate ­ Red (flash)

Calcium nitrate ­ Red (flash) with more yellow

Sodium chloride ­ Brilliant orange

Unknown Solution C ­ Orange and pink with a little white (Potassium nitrate)

Discussion:

What is the Relationship between frequency and wavelength? What happens to energy as wavelength increases? As the frequency goes up, the wavelength goes down. As wavelength increases, the amount of energy goes down.

How do you think metallic salts are used in fireworks? I would guess that the rocket would be filled with the ion of choice (depending on what color was wanted), along with an explosive charge. When the rocket exploded, the electrons would jump to a higher level, and then fall back, producing the color needed in the transition.

Why does the yellow flame around a rod of glass observed only when the glass rod s heated? What does it signify? I would guess that it is the result of electrons jumping down levels, just as in the ionic compounds we tested. It would signify the energy given off in the form of visible light that happens to be yellow.

What ion is responsible for the red in fireworks? I would assume it would be Lithium nitrate, because that produced the most brilliant red of the chemical we tested.

What is the formula for all of the chemicals above?

Barium nitrate ­ Ba(No3)2

Strontium nitrate ­ Sr(No3)2

Copper (II) nitrate ­ Cu(No3)2

Potassium nitrate ­ K(No3)

Lithium nitrate ­ Li(No3)

Calcium nitrate ­ Ca(No3)2

Sodium chloride ­ NaCl

Hydrochloric acid - HCl

Full Electron Configuration of Each Cation

Barium ­ 1S2, 2S2, 2P6, 3S2, 3P6, 4S2, 3D10, 4P6, 5S2, 4D10, 5P6, 6S2

Strontium ­ 1S2, 2S2, 2P6, 3S2, 3P6, 4S2, 3D10, 4P6, 5S2

Copper - 1S2, 2S2, 2P6, 3S2, 3P6, 4S2, 3D9

Potassium ­ 1S2, 2S2, 2P6, 3S2, 3P6, 4S1

Lithium ­ 1S2, 2S1

Calcium ­ 1S2, 2S2, 2P6, 3S2, 3P6, 4S2

Sodium ­ 1S2, 2S2, 2P6, 3S1

Conclusion:

The flame test lab was done so that we could visibly detect the difference between each ionic compound as the electrons were moving from a higher to a lower level. For some compounds, it was easy to tell what color it produced. The Copper (II) Nitrate was the easiest to tell with a bright green flame. Also easily identifiable was the Sodium Chloride, which produced a brilliant orange flame that lasted a long time. This was tested last, because residue of the compound stayed on the wire loop even after cleaning. A few others were also fairly easy to identify. Barium Nitrate produced a yellowish white that was fairly distinguishable, and Lithium Nitrate had a flash of red at the beginning of the burn, and then burned a dull red. After that, the rest weren't as easy to tell. Strontium nitrate burned a yellowish white, and Potassium Nitrate gave off an orange and pink flame, with a little white in it as well. Calcium nitrate was a lot like the Lithium nitrate, but with a more yellow flame. The flame test is a very useful way to determine what ionic compounds might be in a mixture. It would be hard to tell if potassium nitrate, for example, were in the mixture, but certain compounds give off very obvious colors. Copper (II) Nitrate, for example would be easy to tell. The obvious green color would be telling of this compound. Also, even a little but of Sodium Chloride would produce that brilliant orange flame, telling the scientist of its presence. Some of the others would be much harder to tell. With other compounds mixed it, it wold be easy to get Calcium nitrate and Lithium nitrate mixed up, just to mention one. The most interesting thing about this experiment is how we can tell by viewing the visible light of the flame how much energy the compound is producing. A compound with a red flame, for example, would be giving out more energy than one with a violet flame because red is higher in the electromagnetic spectrum. That is one way that this lab is tied into what we're doing in class. In doing this lab, it is easier to see how different compounds produce different amounts of energy, and tying that into what we've learned about the electromagnetic spectrum. This also ties into the Line Spectrum, and Bohr's atomic theory. Since we can determine properties of an element and how it's electrons move by running electricity through it an properly viewing it's line spectrum, we know that each element releases specific amounts and colors in the visible light spectrum. The flame lab is very much the same thing, as each element makes the flame turn a specific color.