Chromatography for Edexcel A-level Chemistry
This page covers the following topics:
3. Rf values
Formulations are complex mixtures of chemicals which have a specific use.
Chromatography can be used to identify the substances present in a mixture of solutes.
Chromatograms can be identified by calculating the Rf values for the separated components of mixtures.
Calculate the Rf value for the blue ink in the chromatogram shown.
In a paper chromatography experiment, the yellow coloured ink is found to not move up the paper. What is the retention factor? Why does the ink not move?
0 - the yellow ink is not soluble in the solvent used.
In a paper chromatogram, the solvent travels 7.2 cm up the paper. The Rf value for red ink is 0.5. How far did the red ink travel up the paper?
Calculate the Rf value for the purple ink in the chromatogram shown.
Which is an example of a formulation: a block of pure iron, cough syrup, oxygen gas.
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