An analytical chemist uses thin-layer chromatography (TLC) to isolate a compound from a natural plant extract.
The Rf R_f\,Rf value of the target compound is determined to be 0.28. Calculate the distance moved by the solvent front, in cm\text{cm}cm, when the spot of the target compound has travelled a distance of 4.2 cm from the baseline. Show your working.
Explain why the Rf R_f\,Rf value of this target compound remains constant even if the solvent front is allowed to run further up the TLC plate.
28 exam-style questions on AQA GCSE Chemistry 8.1 Purity, formulations and chromatography, covering 8.1.1 Pure substances, 8.1.2 Formulations, and 8.1.3 Chromatography. Each one has a worked solution and a mark scheme showing where the marks go.