CAIE A Level Chemistry 9701 · Analytical techniques
A mixture of the alkanes hexane, heptane and octane is separated using gas chromatography. The stationary phase is a high boiling point non-polar liquid coated on a solid support, and the mobile phase is an unreactive gas such as .
Describe the process of separation, and explain how the retention times of the three alkanes would differ from each other.
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.
Describe means: Say what happens or what something is like, in order and with detail. You are not being asked why. If there is data, quote it: name the trend, then give figures with units at the points where it changes.
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