Data Table Sheet 1: FD&C Food Colors Color Blue1 Blue2 R ed3 R ed40 Y ellow5 Y e
ID: 882886 • Letter: D
Question
Data Table Sheet 1: FD&C Food Colors
Color
Blue1
Blue2
Red3
Red40
Yellow5
Yellow6
Solvent
Distance (mm)
Rf
Data Table Sheet 1: Drink Mixes
Substance
Kool-Aid® Grape
Kool-Aid® Strawberry
Solvent
Distance (mm)
Distance (mm)
Rf
Data Table Sheet 2: Store Food Colors
Substance
Store Red
Store Yellow
Store Green
Store Blue
Solvent
Distance (mm)
Rf
Data Table Sheet 2: Candy Colors
Substance
M&M Green
M&M Yellow
M&M Blue
M&M Red
Solvent
Distance (mm)
Rf
Questions
A. Why can’t a pen be used to draw the baseline on the chromatography paper?
B. Why is it important to stop the chromatograph before the solvent reaches the top of the paper?
C. Why is it important to keep the dye spots above the solvent level?
D. Why is it important to mark the solvent level on the chromatography paper when you remove it from the petri dish?
Extra credit and/or extra fun possibilities: Experiment with different solvents such as pure water, rubbing alcohol, or a mixture of alcohol and water. Do not use flammable solvents to experiment! There are often interesting dyes making up the colors of marker pens (especially black). If you want to experiment with marking pens remember not to use permanent ink markers for this experiment.
Data Table Sheet 1: FD&C Food Colors
Color
Blue1
Blue2
Red3
Red40
Yellow5
Yellow6
Solvent
Distance (mm)
Rf
Explanation / Answer
A.
Ink used in pen is made up of various pigments which are capable of getting dissolved in solvent. As a result, there will be separation of components of ink along with the desired mixture. This would interfere with the actual components that we are trying to separate. Therefore a pen cannot be used to draw the baseline on the chromatography paper.
B.
Rf value of a component is the ratio of distance travelled by the solvent to the distance travel by the component.
If we allow the solvent to reach the end of the paper, there would be no more space for the solvent to travel further , but the component will get a chance to travel till it reaches the end of the paper. This would give inaccurate result for the distances travelled and the end result would be very high Rf value which is not accurate.
C.
The dye spot is made of a substances that can be dissolved in the solvent used. If the marked spot is completely immersed in the solvent, the components of the dye will get dissolved in the solvent itself and there would be no separation of the components.
Instead, we mark the spot above the solvent level, so when the solvent reaches the spot, it is able to separate different components based on their Rf values
D.
It is important to mark the solvent level on the chromatography paper because the solvents used for chromatography are volatile. And if we don't mark the level immediately, there is a possibility that it might get evaporated and we cannot draw the exact solvent level. This would give us inaccurate value for distance travelled by the solvent.
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