A chemist recovered a blue dye from wastewater. The chemist compared the recovered sample with a pure sample of dye D using paper chromatography.
In solvent 1, the recovered sample produced one spot with an Rf R_f\,Rf value of 0.60. Dye D also produced one spot with an Rf R_f\,Rf value of 0.60.
The recovered sample and dye D were then placed on the same chromatography paper and tested using solvent 2.
| Result in solvent 2 | Value |
|---|---|
| Distance moved by solvent front | 75 mm |
| Distances moved by spots from recovered sample | 21 mm and 54 mm |
| Rf R_f\,Rf value of dye D | 0.72 |
A student concluded, 'The recovered sample is pure dye D because it produced one spot with the same Rf R_f\,Rf value as dye D in solvent 1.'
Calculate the Rf R_f\,Rf value of each spot from the recovered sample in solvent 2.
Evaluate the student's conclusion. Use the results from both solvents and your answers to part (a).
113 exam-style questions on AQA GCSE Chemistry 8.1 Purity, formulations and chromatography, covering 8.1.1 Pure substances, 8.1.2 Formulations, and 8.1.3 Chromatography. Each one has a worked solution and a mark scheme showing where the marks go.