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You are in the lab and performing a TLC experiment. Unfortunately, you were so i

ID: 912809 • Letter: Y

Question

You are in the lab and performing a TLC experiment. Unfortunately, you were so involved in carrying out a melting point determination that you didn't notice that the solvent front had reached the top of the silica plate.

Are you able to calculate accurate Rf values for the compounds you were looking at?

Maybe, but it will depend on the polarity of the compounds and how far they travelled up the plate.

No, because the Rf value is determined in relation to the solvent front. Without a visible solvent front it is impossible to determine accurate Rf values.

Yes, because the Rf values can be determined by interpolation.

No, because you always need to have a standard present to determine the Rf values of any unknown compounds.

Yes, because the Rf values will be equal to the distance travelled by each spot divided by the distance to the very top of the plate.

A.

Maybe, but it will depend on the polarity of the compounds and how far they travelled up the plate.

B.

No, because the Rf value is determined in relation to the solvent front. Without a visible solvent front it is impossible to determine accurate Rf values.

C.

Yes, because the Rf values can be determined by interpolation.

D.

No, because you always need to have a standard present to determine the Rf values of any unknown compounds.

E.

Yes, because the Rf values will be equal to the distance travelled by each spot divided by the distance to the very top of the plate.

Explanation / Answer

ANSWER:

Option (B) is correct answer. Without solvent front it is not clear how much distance the compound has travelld from base line.

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