A-LevelChemistryAnalytical techniques9701/41 · Oct/Nov 2025 · Q67 Marks

Thin-layer and gas/liquid chromatography can be used to separate mixtures into their individual components. Define the following terms used in chromatography. Rf value retention time [2]

(a)(i)Thin-layer and gas/liquid chromatography can be used to separate mixtures into their individual components. Define the following terms used in chromatography. Rf value ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ retention time ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ [2][2]
(a)(ii)Each type of chromatography makes use of a stationary phase and a mobile phase. Complete Table 6.1 with a description of each of these. Table 6.1 stationary phase mobile phase thin-layer chromatography gas/liquid chromatography [1][1]
(b)A mixture of two substances A and B is analysed by thin-layer chromatography. The Rf value of substance A is larger than that of substance B. Suggest why substance A has a larger Rf value.[1]
(c)(i)The two isomeric compounds Y and Z are analysed by proton (1H) NMR spectroscopy. [Figure for Y and Z] Complete Table 6.2 to predict the number of peaks observed in the proton (1H) NMR spectra for Y and Z. Table 6.2 compound number of peaks observed Y Z [1][1]
(c)(ii)Name all the different splitting patterns observed in the proton (1H) NMR spectra for Y and Z. Y _________________________ Z _________________________ [2][2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2025). The mark or mark type is shown in brackets.

[1] M1: (Rf value) is distance moved by a component / spot / solute AND divided by distance moved by solvent OR (Rf value) is the ratio of distance moved by a component / spot / solute AND by distance moved by solvent
[1] M2: (retention time) is (the time) between injection and detection (of a component)
[1] thin-layer chromatography: polar solvent OR non-polar solvent OR named solvent
[1] gas-liquid chromatography: non-volatile liquid OR high boiling point liquid
[1] A is more soluble in the mobile phase OR A has less adsorption to the stationary phase
[1] Y 2
[1] Z 2
[1] M1: Y (two) singlet(s)
[1] M2: Z triplet AND quartet