A chemist isolates four samples of a fragrance compound from a flower extract. The chemist uses chromatography with three different solvents and records the number of spots produced.
| Sample | Solvent P | Solvent Q | Solvent R |
|---|---|---|---|
| A | 1 | — | — |
| B | 1 | 1 | 1 |
| C | 1 | 1 | 2 |
| D | 2 | 1 | — |
A dash means that chromatography was not carried out using that solvent.
Which sample is supported by the best evidence of being a single pure substance?
Sample C
Sample B
Sample A
Sample D
102 exam-style questions on OCR GCSE Chemistry 2.1 Purity and separating mixtures, covering 2.1.1 Pure substances and melting point data, 2.1.2 Relative formula mass and empirical formula, 2.1.3 Formulations as useful mixtures, 2.1.4 Techniques for separating mixtures, and 2.1.5 Chromatography and Rf values. Each one has a worked solution and a mark scheme showing where the marks go.