A student compares two methods for placing the same purple flower extract on chromatography paper. The same paper and solvent are used for both methods.
The extract contains two coloured substances.
| Method | Diameter of spot placed on the start line in mm | Width of each spot after chromatography in mm | Distance between the centres of the two spots in mm |
|---|---|---|---|
| P | 2 | 3 | 8 |
| Q | 8 | 9 | 8 |
Which method should the student use to obtain the more reliable Rf R_f\,Rf values? Explain your answer using the data.
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.