A technician used paper chromatography to investigate a colourant from a cleaning product. The colourant and pure reference dyes P and Q were tested in two experiments. In each experiment, all three samples were run on the same chromatography paper using the solvent shown.
The table shows the results.
| Solvent | Distance moved by solvent front (cm) | Distance moved by spots from the colourant (cm) | Rf value of dye P | Rf value of dye Q |
|---|---|---|---|---|
| 1 | 8.0 | 4.0 | 0.50 | 0.50 |
| 2 | 10.0 | 3.0 and 7.0 | 0.30 | 0.70 |
Calculate the Rf value of each spot produced by the colourant in both solvents.
A student concludes, ‘The colourant is pure and is dye P.’
Evaluate the student's conclusion. Use all of the results.
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.