Question detail
In Chromatography, which answer best matches the evidence for chromatography?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Purity, formulations and chromatography
Question
- A. Cobalt calculation: Rf = 4 ? 8 = 0.5 using spot distance divided by solvent-front distance
- B. Cobalt calculation: Rf = 8 ? 4 = 2.0 using solvent-front distance divided by spot distance
- C. Cobalt calculation: Rf is found from the colour of the spot rather than distance moved
- D. Cobalt calculation: Rf is found by adding the spot distance and solvent-front distance
Answer
The correct answer is Cobalt calculation: Rf = 4 ? 8 = 0.5 using spot distance divided by solvent-front distance. It matches chromatography because the evidence is spot and solvent-front distances and the expected result is Rf or separation evidence.
Explanation
The correct option is Cobalt calculation: Rf = 4 ? 8 = 0.5 using spot distance divided by solvent-front distance. This is correct because spot and solvent-front distances is the evidence expected for chromatography, and Rf or separation evidence is the result that supports the conclusion. Other options are weaker when they confuse gas tests, flame colours, ion-test precipitates, chromatography evidence, or pure-substance/formulation wording.
Common mistake
Misunderstanding Rf Value Calculation
Students often confuse the distances moved by the substance and the solvent when calculating Rf values.
Ensure to measure the distance moved by the substance and the distance moved by the solvent separately, then use the formula Rf = distance moved by substance / distance moved by solvent.
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