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A student investigated green ink using paper chromatography in a beaker - AQA - GCSE Chemistry - Question 4 - 2020 - Paper 2

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A student investigated green ink using paper chromatography in a beaker. The student used water as the solvent. Figure 2 shows the chromatogram obtained. The Rf va... show full transcript

Worked Solution & Example Answer:A student investigated green ink using paper chromatography in a beaker - AQA - GCSE Chemistry - Question 4 - 2020 - Paper 2

Step 1

Calculate the distance moved by the solvent.

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Answer

To calculate the distance moved by the solvent, we use the Rf formula:

Rf=distance moved by substancedistance moved by solventR_f = \frac{\text{distance moved by substance}}{\text{distance moved by solvent}}

Given that the Rf value of the yellow dye is 0.60 and the distance moved by the yellow dye is 5.7 cm, we can rearrange the formula to find:

distance moved by solvent=distance moved by substanceRf\text{distance moved by solvent} = \frac{\text{distance moved by substance}}{R_f}

Thus, substituting in the values:

distance moved by solvent=5.7 cm0.60=9.5 cm\text{distance moved by solvent} = \frac{5.7 \, cm}{0.60} = 9.5 \, cm

Step 2

Suggest one reason why only two spots are seen on Figure 2.

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Answer

Some of the compounds in the green ink may be colorless in solution, which would mean they do not produce visible spots in the chromatogram.

Step 3

Which two ways could increase the distance between the spots?

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Answer

  1. Allow the solvent front to travel further.

  2. Use a different solvent.

Step 4

Suggest one reason why the manufacturers of the green ink always use the same proportions of yellow dye and blue dye.

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Answer

This ensures that the shade of green remains consistent across different batches of the ink.

Step 5

Which will definitely produce a smaller Rf value if the solvent and paper are both changed?

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Answer

The dye is less soluble in the new solvent and less attracted to the new paper.

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