3) Please order the following compounds in order of a) increasing retention time

Question

3) Please order the following compounds in order of a) increasing retention time in a GC

analysis, b) increasing Rf value in a TLC experiment. (Please assume that the separation

conditions for both analytical techniques are optimized.)

Can you change the analytical conditions so that the order of elution from a GC column is

inverted? Please explain.

4) In a GC-separation of a mixture of three compounds consisting of 1 mol A, 1 mol B, and

1 mol C, the peak area (integral) produced by the response of the detector is:

Compound A: 10 Compound B: 50 Compound C: 25

The separation of a second mix of the same compounds with an unknown composition

leads to the following peak areas:

Compound A: 100 Compound B: 40 Compound C: 10

Please calculate the response ratio of your compounds if you choose compound B as your

standard. What is the molar composition of the second mixture (show your calculations)?

5) Why are London Dispersion forces of the sample molecules strongly influencing GC

measurements? And why are they usually negligible in TLC experiments on silica gel?

6) If a GC separation is performed on a nonpolar and slightly more polar column (same

length), which of the following sentences is most correct. Please explain your answer.

a) On a more polar column, molecules that are more polar will have longer ret. times.

b) On a more polar column, nonpolar compounds will have shorter retention times.

c) On a more polar column, all molecules will have longer retention times.

d) On a more polar column, retention times will be unchanged.

7) The following two compounds are very similar, yet the retention times are surprisingly

different (more than one minute difference in a ten-minute measurement). Which of the

two compounds would you expect to have a lower retention time? Please explain.

8) Please explain why diffusion broadens the peaks in gas chromatography

Please answer

Please order the following compounds in order of a) increasing retention time in a GC analysis, b) increasing Rf value in a TLC experiment. (Please assume that the separation conditions for both analytical techniques are optimized.) Can you change the analytical conditions so that the order of elution from a GC column is inverted? Please explain. In a GC-separation of a mixture of three compounds consisting of 1 mol A, 1 mol B, and 1 mol C, the peak area (integral) produced by the response of the detector is: Compound A: 10 Compound B: 50 Compound C: 25 The separation of a second mix of the same compounds with an unknown composition leads to the following peak areas: Compound A: 100 Compound B: 40 Compound C: 10 Please calculate the response ratio of your compounds if you choose compound B as your standard. What is the molar composition of the second mixture (show your calculations)? Why are London Dispersion forces of the sample molecules strongly influencing GC measurements? And why are they usually negligible in TLC experiments on silica gel? If a GC separation is performed on a nonpolar and slightly more polar column (same length), which of the following sentences is most correct. Please explain your answer. On a more polar column, molecules that are more polar will have longer ret. times. On a more polar column, nonpolar compounds will have shorter retention times. On a more polar column, all molecules will have longer retention times. On a more polar column, retention times will be unchanged. The following two compounds are very similar, yet the retention times are surprisingly different (more than one minute difference in a ten-minute measurement). Which of the two compounds would you expect to have a lower retention time? Please explain. Please explain why diffusion broadens the peaks in gas chromatography Please answer

Explanation / Answer

8) Please explain why diffusion broadens the peaks in gas chromatograph

diffusion may explain the increase in the width of the chromatographic peak

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