Lab 4: TLC

Question 1

What is the compound that can be used as the absorbent on a TLC plate?

Answer 1

silica gel

Question 2

At what time should the solvent from a TLC plate be marked?

Answer 2

Immediately after the separation is stopped

Question 3

After removing a TLC plate from the developing chamber, what is the first thing to do with the plate?

Answer 3

Draw the solvent front line

Question 4

In order to visualize these compounds under a UV light, the compound must

Answer 4

absorb UV light

quench the fluorescence of the absorbant

Question 5

What is the force responsible for the upward movement of the eluent on a TLC plate?

Answer 5

capillary action

Question 6

For TLC, a larger Rf value means

Answer 6

a larger distance on the TLC plate

Question 7

A student develops their TLC plate and places it under a UV light, but nothing appears. What mistake might the student have made?

Answer 7

spotted the compound below the level of the eluent

Question 8

A mixture of two compounds on a TLC plate will move a short distance and appear as a single spot only if a very polar solvent is used. Which two ways should the system be adjusted for better results?

Answer 8

using a less polar eluent and a less active absorbent (stationary phase)

Question 9

A TLC plate was run in 1:1 toluene:ethyl acetate, but when developed the plate only showed baseline spots. What change could be made to get the spots to move further up the plate?

Answer 9

Spot a new plate and run in 1:2 toluene:ethyl acetate

Question 10

Which compound is not sold as an over-the counter drug?

Answer 10

cortisone

Question 11

Another name for caffeine is `

Answer 11

1,3,7-trimethyl-2,6-dioxopurine