A team of four students isolated the components of a mixture and then verfied th

Question

A team of four students isolated the components of a mixture and then verfied the purity and identitiy of each compound by comparing its movement on a TLC plate with that of reference samples. Each student developed the plate with a solvent he chose and located the sample spots with a UV light to determine the Rf vaule of each.

Student A found one spot in each lane, each with Rf vaule of ~0. Student B also found one spot in each lane with an Rf vaule of 0.55. Both students concluded that their isolated component was identical to the reference tested. Is that a valid conclusion? To answe address the following:

Is there eveidence that the partitioning between mobile and stationary phases necessary to separate species on TLC took place in each?

Descibe what you know about the samples and solvents used by student A?

Which student has better reason to think the conclusion about his anaylsis valid? Why?

Explanation / Answer

the conclution may be valid.partitioning between mobile and stationary phases plays a role. A component in TLC need not to have constant Rf value in all solvents.Rf is based on polarity of that particular component and the solvent.

In student A case both sample and solvent may be the same so he got zero Rf. student B select a solvent in which the component is in intermediate polarity I think student A have a better reasoning.

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