Chromatography

Question 1

What is chromatography

Answer 1

Used to separate mixtures of soluble substances and to provide information on the possible identities of substances present in the mixture. They are often coloured substances such as inks or dyes.

Question 2

The 2 phases of chromatography

Answer 2

The mobile phase is the solvent that moves through the paper and carries the substance with it.
The stationary phase is contained on the paper and does not move through it

Question 3

Interpreting a chromatogram

Answer 3

Separation by chromatography produces a chromatogram and can distinguish a pure and impure substance. A pure substance produces one spot on the chromatogram whereas an impure substance has 2 or more.

Question 4

Interpreting a chromatogram pt 2

Answer 4

It can also identify substances by comparing them with known substances. Two substances are likely to be the same if:
They produce the same amount of spots and they match in colour
The spots travel the same distance up the paper (same rf value)

Question 5

What are Rf values

Answer 5

Rf values can be used to identify unknown chemicals if they can be compared to a range of reference substances. Rf value= distance travelled from substance/distance travelled from solvent. Rf values vary from 0 (substance isnt attracted to mobile phases) to 1 (substance isnt attracted to stationary phase)