IGCSE/ A-Level Revision Questions

Question 3

The chromatogram below shows the results of a paper chromatography experiment on two unknown substances, labelled P and Q. The solvent used was hexane. The Rf values are shown in the table below.

Substance

Rf Value

0.10

0.95

State whether substance P is pure or impure. Justify your answer using information from the chromatogram.

Answer:

Answer: Substance P is impure.

Justification: A pure substance will only consist of one component and will therefore produce a single spot on the chromatogram. Substance P has an Rf value of 0.10. Substance Q has an Rf value of 0.95. Since substance P produces a single spot, it may appear pure. However, the fact that it has a significantly lower Rf value than substance Q suggests that it contains other components that are not being separated by the solvent. If P were pure, it would have produced a different Rf value than Q. Therefore, P is impure.

Chemistry – Experimental techniques and chemical analysis - Chromatography | e-Consult

Experimental techniques and chemical analysis - Chromatography (1 questions)

Question 3