A student measures the distances on a chromatogram from the bottom edge of the paper instead of from the start line. The start line is 1.5 cm above the bottom edge of the paper.
| Measurement | Distance from bottom edge of paper (cm) |
|---|---|
| Centre of spot | 4.2 |
| Solvent front | 7.5 |
What is the correct Rf value of the spot?
0.36
0.45
0.56
0.70
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.