CAIE A Level Chemistry 9701 · Analytical techniques
A mixture of three organic compounds, X, Y, and Z, is analysed by gas-liquid chromatography using a non-polar stationary phase and an inert carrier gas. The table shows the retention times and relative peak areas obtained.
| Compound | Retention time / min | Relative peak area |
|---|---|---|
| X | 2.5 | 120 |
| Y | 5.0 | 80 |
| Z | 8.0 | 200 |
Compare the interactions of X, Y, and Z with the stationary phase, and explain what the relative peak areas indicate about the composition of the mixture.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Compare means: Give similarities or differences between two things, and say which side each point belongs to. Write each point as a pair, for example: A is X, whereas B is Y. Two separate descriptions rarely earn the marks.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.