Separating Molecules (2.1.2)

Question 1

What are the two phases in chromatography?

Answer 1

Mobile phase

Stationary phase

Question 2

What is a mobile phase?

Answer 2

In thin-layer chromatography, it is a solvent, such as ethanol or water.

Question 3

What is a stationary phase?

Answer 3

In paper chromatography, it is a piece of chromatography paper.

In thin-layer chromatography, it is a layer of solid. e.g. silica gel on a glass or plastic plate.

Question 4

What is the basic principle of chromatography?

Answer 4

The mobile phase moves through or over the stationary phase.

The components in the mixture spend different amounts of time in the mobile and stationary phases.

Components that spend longer in the mobile phase travel faster or further

Question 5

What is the process for separating amino acids?

Answer 5

Draw a pencil line near the bottom of the paper.

Drop a concentrated spot of the mixture on the line.

Add the solvent (mixture of butan-1-ol, ethanoic acid and water)

Dip the paper into the solution

Cover with a lid to prevent the solvent from evaporating

When the solvent has reached the top, remove the paper and draw a pencil line

Leave to dry

Spray ninhydrin solution onto the paper to turn the amino acids purple

Question 6

What are Rf values?

Answer 6

The ratio of the distance travelled by a solute to the distance travelled by the solvent.

Question 7

How do you calculate an Rf value?

Answer 7