A forensic scientist investigates a forged note. She puts a spot of ink taken from the note and a spot of ink from each of four pens, J to M, on one sheet of chromatography paper. She develops the paper in a single solvent.
| Ink sample | Rf value of each spot |
|---|---|
| Ink from note | 0.28 and 0.61 |
| Pen J | 0.28 and 0.75 |
| Pen K | 0.28, 0.46 and 0.61 |
| Pen L | 0.28 and 0.61 |
| Pen M | 0.61 |
Which pen was most likely used to write the note?
Pen K
Pen L
Pen M
Pen J
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.