Unit Three, Chapter Thirty Seven - Chromatography

Question 1

What is chromatography?

Answer 1

A technique used to separate the components present within a mixture

Question 2

How does chromatography work?

Answer 2

Separates substances by making use of differences in their polarity or molecular size

Question 3

Describe the stages of TLC

Answer 3

(1) A small sample of the mixture being tested is spotted onto the base line of the chromatogram
(2) A solvent dissolves the compounds in the spot and carries the compounds up the chromatogram
(3) How far the compounds are carried depends on solubility in the chosen solvent and how well they adhere to the plate
(4) A developing agent or UV light is often required to visualise the spots

Question 4

What is the main piece of equipment required for TLC?

Answer 4

Fine film of silica or aluminium oxide spread over glass

Question 5

How to calculate Rf values

Answer 5

Rf = distance travelled by the sample/distance travelled by the solvent

Question 6

What is TLC used for?

Answer 6

To assess the purity of substances by determining what substances are present

Question 7

The presence of only one spot indicates…

Answer 7

That the substance is pure

Question 8

The presence of more than one spot indicates…

Answer 8

That impurities are present