Question

1. Write the one property of chemicals that is most relevant to the process of separation by TLC or column chromatography. Then circle the one most correct among the following choices for whether that property is specifically about: "individual atom(s)", "individual bond(s)", or "the net effect/the molecule as a whole".

2. If one analyte substance is more polar than another, how will the progression of this more-polar analyte through your chromatography column compare to the less-polar one? Choose among: "move more rapidly", "move less rapidly", "probably move differently but cannot predict more/less rapidly", "move about the same", or "depends on polarity of solvent (mobile phase)".

3. If one mobile phase (solvent) is more polar than another, how will the progression of an analyte substance on your TLC plate using this more-polar mobile phase compare to the progression of this same analyte using the less- polar one? Choose among: "move further", "move less far", "probably move differently but cannot predict more/less far", "move about the same", or "depends on polarity of analyte".

4. If one measures the TLC distances using the units of measurement as instructed, what will be the unit of measurement for the calculated Rf values?

Answer 1

1.

Answer is "the net effect/the molecule as a whole".

The process of separation by TLC or column chromatography. depends on the polarity of the whole molecule.

2.

One analyte substance is more polar than another,

Answer is "move less rapidly" and "depends on polarity of solvent (mobile phase)".

If your polar substance is more polar and you develop the TLC or run the column chromatography with non-polar solvent such as hexane; you compound maynot move at all. So, it will depend of the polarity of the mobile phase. If the polarity of the mobile phase is sufficient enough to move both the substances, then the mole polar substance will have less Rf value than the less polar substance.  

"depends on polarity of solvent (mobile phase)" is the most appropriate answer.

3.

one mobile phase (solvent) is more polar than another

Answer is "move further" and "depends on polarity of analyte".

Eplanation is as same as 2.

"depends on polarity of analyte" is the most appropriate answer.

4.

Rf value has no unit.

Rf value is defined as the ratio of the distance moved by the solute (i.e. the compound under test) and the distance moved by the the solvent (known as the Solvent front) along the TLC.