A chemist places one spot of a mixture containing substances P and Q on each of two identical TLC plates coated with silica gel. The chemist uses a different solvent with each plate.
The table shows the distances moved from the start line.
| Solvent | Distance moved by P in cm | Distance moved by Q in cm |
|---|---|---|
| W | 4.0 | 4.0 |
| X | 2.0 | 6.0 |
Which statement identifies the solvent that separates P and Q better and explains why?
Solvent W, because P and Q both dissolve in it, so they move the same distance.
Solvent W, because a single spot shows that the mixture has been fully separated.
Solvent X, because P spends more time dissolved in the solvent than Q does.
Solvent X, because P and Q are distributed differently between the solvent and the silica gel.
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.