You wish to analyze the purity of a compound via TLC. If you wanted polar compou

Question

You wish to analyze the purity of a compound via TLC. If you wanted polar compounds to remain near the bottom (or baseline) of the plate, what kind of TLC plate would you use?

a. A normal phase TLC plate because the nonpolar stationary phase will interact with nonpolar compounds more strongly.

b. A reverse phase TLC plate because the polar stationary phase will interact with polar compounds more strongly.

c. A reverse phase TLC plate because the nonpolar stationary phase will interact with polar compounds more strongly.

d. A normal phase TLC plate because the polar stationary phase will interact with polar compounds more strongly.

2. You decide to use a plastic-backed TLC plate coated in silica gel. Which of the following choices is the stationary phase?

a.

The solvent vapors in the developing chamber

The substance or mixture to be separated

The plastic of the TLC plate

The liquid solvent in the developing chamber

The silica gel on the TLC plate

You are deciding which solvents to use to develop your TLC plate. Order the following solvents from most polar to least polar.

Dichloromethane, toluene, acetone, isopropanol.

4. You develop and visualize the plate and are not satisfied with the results. Which of the following experimental parameters would result in NO change in retention factors if you were to modify them in a properly performed TLC analysis?

a. width of TLC plate

b. chaning the type of TLC plate

c. volume of solvent in the TLC chamber

d. changing the solvent system polarity

e. size of the initial spot

5. You developed the silica gel TLC plate using 100% ethyl acetate. Which of the following solvent systems would result in higher retention factors if you were to analyze the sample via TLC the same way again?

100% ethanol

50% ethanol/50% ethyl acetate

50% hexanes/50% ethyl acetate

100% hexanes

d. A normal phase TLC plate because the polar stationary phase will interact with polar compounds more strongly.

Explanation / Answer

1.c. A reverse phase TLC plate because the nonpolar stationary phase will interact with polar compounds more strongly
2.B.The substance or mixture to be separated
3.C.acetone
4.a. width of TLC plate
5.b.50% ethanol/50% ethyl acetate

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