Two different compounds were run on the same paper in the same solvent and gave spots with the same Rf R_f\,Rf value.
Which statement about this result is correct?
The result is impossible, because different compounds always have different RfR_fRf values
The result shows that one of the two compounds must be an impure substance
The result means a second solvent is needed to tell the two compounds apart
The result means that the two distances have been measured incorrectly
40 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.