chromatography [O1] PAPER 2

Question 1

State in general terms what determines the distance travelled by a spot in
TLC.

Answer 1

relative affinity for stationary and mobile phases

Question 2

To obtain the chromatogram, the TLC plate was held by the edges and placed in the solvent in the beaker in the fume cupboard. The lid was then replaced on the beaker.
Give one other practical requirement when placing the plate in the beaker.

Answer 2

solvent must be below the start line

Question 3

Answer 3

Question 4

what is thin-layer chromatography (TLC)?

Answer 4

a plate is coated with a solid and a solvent moves up the plate

Question 5

what is column chromatography (CC)?

Answer 5

a column is packed with a solid and a solvent moves down the column

Question 6

what is gas chromatography (GC)?

Answer 6

a column is packed with a solid or with a solid coated by a liquid, and a gas is passed through the column under pressure at high temperature

Question 7

Answer 7

solvent depth must be below the start line

Question 8

A sample of cyclohexene has been contaminated with cyclohexanol. The cyclohexene can be separated from the cyclohexanol by column chromatography.
Silica gel is used as the stationary phase and hexane as the mobile phase.
Explain why cyclohexene has a shorter retention time than cyclohexanol.

Answer 8

• cyclohexene is less polar than cyclohexanol
• cyclohexene has a greater affinity to the mobile phase