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.