A technician uses thin layer chromatography to separate the coloured substances in a plant extract. Each silica-gel plate stands in solvent in a covered beaker. The start line and the solvent depth are measured from the bottom of each plate.
| Setup | Height of start line / mm | Depth of solvent / mm |
|---|---|---|
| A | 14 | 20 |
| B | 14 | 6 |
Explain which setup the technician should use.
One of the setups is unsuitable.
Suggest one change to that setup, using the data in the table, so that it could be used.
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.