Why can\'t you use pen to mark the chromatography paper in this experiment? 2.)
ID: 951872 • Letter: W
Question
Why can't you use pen to mark the chromatography paper in this experiment? 2.) Why is it important to stop the chromatograph before the solvent reaches the top of the paper? What would happen if you allowed the paper to sit in the solvent for 10 minutes after the solvent had reached the top? Explain as specifically as possible. 3.) There are two major components in the chromatography experiment the solvent system (mobile phase) and the paper (stationary phase) Which of these major components is more polar phase and which is less polar phase? Explain using Lewis structures. 4.) The solvent in the developing tank is only 1 1/2 cm high and the samples are spotted at about 3 cm. Why is it important to keep the spots above the solvent? Explain precisely.Explanation / Answer
1.
The pen is a mixture of polar solvents, therefore, when adding it to the mobile phase, they will also move along the path according to their polar affinities
2.
If it reaches the top, the convectin forces will break, moving ceratin species. It is recommended to state a line about 1-2 cm before it finishes
if you let it 10 minutes, then species will change its Rf value, which is essentially just their affinity to the mobile/stationary phases, then they will be interrumpted/changed.
3.
Polar phase --> the stationary phase, since it is silica gel
nonpolar phase --> the mobile phase, since it is a nonpolar solvent, which carries along al nonpolar substance
4.
the solvent must start from the beginning (i..e the level we chose first).
The spots must be above in order for the spot materials not to dilute in the mobile phase (under). That is, we jsut want the spots substances to be carried by the mobile phase, not to dissolve them in the bottom
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