CAIE A-Level Chemistry 37.1.3 Differences in TLC Rf Values
Practise explaining different TLC travel distances through mobile-phase solubility and stationary-phase attraction.
- Syllabus
- 2028–2030
- Course
- Chemistry 9701
- Level
- A2
Exam points
- explain a larger Rf by greater solubility in the mobile phase or weaker adsorption to the stationary phase
- explain a smaller Rf by lower mobile-phase solubility or stronger attraction to the stationary phase
- when the solvent changes, compare relevant intermolecular forces rather than assuming polarity alone fixes movement
37.1.3—Differences in Rf values question 1
A student uses thin-layer chromatography (TLC) to analyse a mixture containing different metal cations. The student repeats the experiment using different solvents.
Fig. 6.1 shows the chromatogram obtained by the student using water as a solvent.
Fig. 6.1
The student repeats the experiment using butan-1-ol as a solvent.
The metal cations do not travel as far up the TLC plate in this experiment.
Suggest why the metal cations do not move as far up the TLC plate with butan-1-ol as a solvent.
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