A-LevelChemistryAnalytical techniques9701/43 · Oct/Nov 2025 · Q67 Marks

(a) Thin-layer and gas/liquid chromatography can be used to separate mixtures into their individual components. (i) Define the following terms used in chromatography. Rf value retention time [2] (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] [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) The two isomeric compounds Y and Z are analysed by proton (1H) NMR spectroscopy. [Figure Y.Y] (i) Complete Table 6.2 to predict the number of peaks observed in the proton (1H) NMR spectra for Y and Z. [Table 6.2] [1] (ii) Name all the different splitting patterns observed in the proton (1H) NMR spectra for Y and Z. Y Z [2]

(a)(i)Define the following terms used in chromatography. Rf value retention time[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][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)Complete Table 6.2 to predict the number of peaks observed in the proton (1H) NMR spectra for Y and Z. [Table 6.2][1]
(c)(ii)Name all the different splitting patterns observed in the proton (1H) NMR spectra for Y and Z. Y Z[2]

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Mark scheme

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

[2] (a)(i) 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 M2: (retention time) is (the time) between injection and detection (of a component)
[1] (a)(ii) thin-layer chromatography: polar solvent OR non-polar solvent OR named solvent gas-liquid chromatography: non-volatile liquid OR high boiling point liquid
[1] (b) A is more soluble in the mobile phase OR A has less adsorption to the stationary phase
[1] (c)(i) compound | number of peaks observed Y | 2 Z | 2
[2] (c)(ii) M1: Y (two) singlet(s) M2: Z triplet AND quartet

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