Chromatography

Question 1

What is chromatography?

Answer 1

A technique used to separate the components present within a mixture.

Question 2

Chromatography separates substances by making use of their?

Answer 2

Different polarity or molecular size

Question 3

What happens in thin-layer chromatography (TLC)?

Answer 3

Uses a fine film of silica or aluminium oxide spread over glass, aluminium foil or plastic. A small sample to be tested is blotted onto the chromatogram. A developing agent or UV light is normally required to visualise spots on the chromatogram.

Question 4

How far compounds are carried depends on?

Answer 4

How soluble the compounds are in the chosen solvent and how well they adhere to the plate.

Question 5

How can Rf values be calculated?

Answer 5

Distance travelled by the sample
____________________________________
Distance travelled by the solvent

Question 6

Under the same conditions a compound always has the same?

Answer 6

Rf value

Question 7

TLC is used to assess?

Answer 7

Purity of substances

Question 8

How does a pure substance show up on a TLC plate?

Answer 8

As a single spot (some impurities may not be visible by TLC analysis) The presence of more than one spot shows that impurities are present