A scientist analysed a coloured sample extracted from seaweed by paper chromatography. Reference pigments P and Q were analysed under the same conditions.
| Solvent | Rf R_f\,Rf values for the seaweed sample | Rf R_f\,Rf value for pigment P | Rf R_f\,Rf value for pigment Q |
|---|---|---|---|
| A | 0.26, 0.54 | 0.54 | 0.54 |
| B | 0.18, 0.67, 0.84 | 0.67 | 0.39 |
Explain what these results show about the number of substances in the seaweed sample.
Explain why pigment P has a higher Rf R_f\,Rf value in solvent B than in solvent A.
Give one reason why the results in solvent B are more useful than the results in solvent A for deciding whether the seaweed sample contains pigment P.
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.