CAIE A Level Chemistry 9701 · Analytical techniques
A student separates a mixture of two coloured dyes, P and Q, using column chromatography. The column is packed with aluminium oxide, a polar stationary phase, and the dyes are eluted with a non-polar solvent. The solvent front travels 12 cm from the baseline. Dye P travels 9 cm and dye Q travels 3 cm.
Suggest why dye P has a higher Rf value than dye Q.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Suggest means: Apply what you know to an unfamiliar situation. There may be more than one acceptable answer. Reason from the principle you have learned to the new context, and say which principle you are using.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.