2018 O Level Chem P1 Q2 — Methods of Purification / Chromatography Solution
Question
The diagram shows the results of a chromatography experiment to identify the dyes present in a sample of ink. Which two dyes make up the ink sample?
Correct answer: B
Video Solution
Explanation
Answer: B (1 and 5). In paper chromatography a component of a mixture travels the same distance up the paper (same \(R_f\)) as a pure sample of that component, so the ink's spots line up horizontally with the spots of its component dyes.
The ink lane shows three spots: one near the top and two low down near the start line. The top spot is level with the top spot of lane 5; the two lower spots are level with the single spot of lane 1 and the lower spot of lane 5.
Together, dyes 1 and 5 account for exactly the three ink spots. Dyes 2, 3 and 4 carry spots at heights the ink does not show, so they are not present. Answer B.
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