Identical spots of a green leaf pigment, L, are placed on two different types of chromatography paper. The same solvent is used for the same length of time.
Pigment L has an Rf R_f\,Rf value of 0.72 on paper A and 0.29 on paper B.
Why is the Rf R_f\,Rf value lower on paper B?
The solvent moves more slowly through paper B, so the ratio used to calculate the RfR_fRf value decreases.
Pigment L is attracted less strongly to paper B, so it remains closer to the origin line.
Paper B acts as the mobile phase, so it moves pigment L a shorter distance than the solvent does.
Pigment L is attracted more strongly to paper B, so it spends less time moving with the solvent.
113 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.