A forensic scientist compares the ink on a letter with the inks from three pens, X, Y and Z. Chromatograms of each ink are run in two different solvents.
| Ink | Rf values in solvent 1 | Rf values in solvent 2 |
|---|---|---|
| Letter | 0.30 and 0.72 | 0.44 and 0.61 |
| Pen X | 0.30 and 0.72 | 0.44 and 0.61 |
| Pen Y | 0.30 and 0.72 | 0.25 and 0.61 |
| Pen Z | 0.30 | 0.44 |
Which pen or pens could have been used to write the letter?
Pen X only
Pen Y only
Pens X and Y only
Pens X, Y and Z
51 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.