4.6.4 Chromatography

Question 1

What is chromatography?

Answer 1

A method of separating mixtures - usually dyes.

Question 2

How do you do paper chromatography?

Answer 2

• Draw a line near the bottom of the chromatography paper in pencil. (use pencil so it will not dissolve in the solvent).
• Add dots of different dyes to the line at regular intervals.
• Place the paper into a beaker of solvent. Make sure the solvent is below the pencil line to stop the inks dissolving.
• Place a lid on the beaker to stop the solvent evaporating.
• Allow the solvent to move up the paper until it is just below the top.
• Take the paper out and mark where the solvent has reached, this is called the solvent front.
• Allow the paper to dry.

Question 3

How does chromatography work?

Answer 3

The dyes move up the page at different rates. The more soluble the dye is in that solvent, the further up the page it will go. If the dye is insoluble it will not move up from the baseline. This means the different dyes will separate based on their solubility.

Question 4

How do you calculate an Rf value?

Answer 4

Rf = distance moved by spot / distance moved by solvent