O-LevelChemistryBonding & Structure5070/12 · Oct/Nov 2017 · Q51 Mark

A chemist wishes to separate and identify a mixture of substances using paper chromatography. The diagram shows the apparatus used. The solvent is water. The solvent front is allowed to reach the top of the paper before the chemist removes the paper from the solvent. Which problem does this cause?

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AThis causes the spot nearest the bottom of the paper to catch up with the spot above it.

BThis makes it impossible to calculate Rf values.

CThis makes it impossible to use a locating agent.

DThis results in a safety hazard caused by solvent fumes.

✓ Correct answer

B: This makes it impossible to calculate Rf values.

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Topic: Bonding & Structure, O-Level Chemistry (syllabus 5070). Multiple choice, 1 mark.
Source: O-Level Chemistry, Oct/Nov 2017 Paper 1 Variant 2, question 5.

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