CAIE IGCSE Chemistry Calculating and Using Rf Values

Practise measuring travel distances from the baseline, calculating Rf values and comparing results obtained under the same chromatography conditions.

Exam points

calculate Rf by dividing distance travelled by the substance by distance travelled by the solvent front
measure both distances from the baseline and check that a valid Rf value does not exceed one
identify a substance by comparing its Rf with a reference measured under the same conditions

[Maximum number: 1]

Chromatography can be used to test the purity of substances.

The diagram shows the chromatogram of a coloured substance.

Draw a circle round the correct $R_{\mathrm{f}}$ value for the spot labelled X.
0.2
0.4
0.8
1.2

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