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A student uses paper chromatography to separate the pigments found in spinach leaves.

At the end of the chromatography experiment:

  • The solvent front has traveled 74 mm74\text{ mm}74 mm from the pencil start line.
  • One of the separated yellow-green pigments has traveled 48 mm48\text{ mm}48 mm from the pencil start line.
a.

Calculate the RfR_{\text{f}}Rf​ value of this yellow-green pigment. Give your answer to 2 significant figures.

[2]
b.

Another separated pigment, pigment Z, is found to have an RfR_{\text{f}}Rf​ value of 0.380.380.38. The student knows that a reference sample of lutein has an RfR_{\text{f}}Rf​ value of 0.550.550.55 under the same experimental conditions.

The student claims that pigment Z is lutein. Explain why the student is incorrect.

[2]
c.

In this paper chromatography experiment, identify:

  1. the stationary phase
  2. the mobile phase
[2]

Purity and separating mixtures Questions

Practise OCR GCSE Chemistry Purity and separating mixtures with exam-style questions for Foundation and Higher tier. 81 questions, matched to the OCR GCSE Chemistry (J248) specification and written in Paper 1 and Paper 2 (Foundation Tier) or Paper 3 and Paper 4 (Higher Tier) style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.

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Purity and separating mixtures Questions

  1. GCSE
  2. /Chemistry
  3. /Purity and separating mixtures