Chromatography

Practice Questions

GRE Subject Test: Chemistry › Chromatography

Questions
8
1

A chemist carries out the synthetic scheme shown below. Unfortunately, the first two reactions are incomplete, and a mixture of compounds A, B, and C is obtained after the second step. The chemist purifies this mixture by normal phase chromatography, using silica gel as a stationary phase and a 10:1 hexanes-diethyl ether (v:v) solution as an eluent. In what order would compounds A, B, and C elute off the column?

For each choice, the first compound to elute is listed first.

Mcat_1

2

A chemist carries out the synthetic scheme shown below. Unfortunately, the first two reactions are incomplete, and a mixture of compounds A, B, and C is obtained after the second step. The chemist purifies this mixture by normal phase chromatography, using silica gel as a stationary phase and a 10:1 hexanes-diethyl ether (v:v) solution as an eluent. In what order would compounds A, B, and C elute off the column?

For each choice, the first compound to elute is listed first.

Mcat_1

3

Chromatography involves the separation of a mixture by allowing a mobile phase to travel along a stationary phase. In thin layer chromatography (TLC), a liquid solution is able to travel along a stationary plate. The distance that a particular compound travels compared to another compound can be determined by comparing the Rf factors for each compound. The Rf factor is determined by dividing the compound's distance by the total distance of the solvent.

Which of the following compounds would have the smallest Rf factor in a standard thin-layer chromatography (TLC) experiment?

4

Chromatography involves the separation of a mixture by allowing a mobile phase to travel along a stationary phase. In thin layer chromatography (TLC), a liquid solution is able to travel along a stationary plate. The distance that a particular compound travels compared to another compound can be determined by comparing the Rf factors for each compound. The Rf factor is determined by dividing the compound's distance by the total distance of the solvent.

Which of the following compounds would have the smallest Rf factor in a standard thin-layer chromatography (TLC) experiment?

5

Which of the following functional groups would be expected to have the largest value during a thin-layer chromatography (TLC) experiment with an ether solvent?

6

Which of the following functional groups would be expected to have the largest value during a thin-layer chromatography (TLC) experiment with an ether solvent?

7

Which of the following purification techniques would best separate a nonpolar solute from a polar solute?

8

Which of the following purification techniques would best separate a nonpolar solute from a polar solute?

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