P, Q, R and S are mixtures of food colourings. They are investigated using paper chromatography. Figure 4 shows the chromatogram at the end of the experiment. (i) Which mixture contains an insoluble food colouring? A mixture P B mixture Q C mixture R D mixture S (ii) Give a change that could be made to the experiment to obtain an Rf value for the insoluble colouring. (iii) Explain, by referring to Figure 4, which mixture is separated into the greatest number of soluble food colourings by this chromatography experiment.

GCSE Edexcel Chemistry Reactions of acids: P, Q, R and S are mixtures of fo

P, Q, R and S are mixtures of food colourings - Edexcel - GCSE Chemistry - Question 3 - 2016 - Paper 1

Question 3

P, Q, R and S are mixtures of food colourings. They are investigated using paper chromatography. Figure 4 shows the chromatogram at the end of the experiment. (i) W... show full transcript

Worked Solution & Example Answer:P, Q, R and S are mixtures of food colourings - Edexcel - GCSE Chemistry - Question 3 - 2016 - Paper 1

Step 1

Which mixture contains an insoluble food colouring?

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Answer

From the chromatogram shown in Figure 4, the mixture that does not produce any spots on the chromatogram is indicative of an insoluble food colouring. In this case, this is mixture S, as it shows no separation or spot formation.

Step 2

Give a change that could be made to the experiment to obtain an Rf value for the insoluble colouring.

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Answer

A change that could be made to the experiment to obtain an Rf value for the insoluble colouring would be to use a different solvent or solvent mixture that may dissolve the insoluble food colouring. Additionally, increasing the chromatography time might ensure that more components are separated.

Step 3

Explain, by referring to Figure 4, which mixture is separated into the greatest number of soluble food colourings by this chromatography experiment.

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Answer

Referring to Figure 4, mixture Q shows multiple spots, which indicates that it contains the greatest number of soluble food colourings. The more distinct spots observed, the greater the number of soluble substances present, meaning mixture Q has effectively separated into several components during the paper chromatography process.

P, Q, R and S are mixtures of food colourings - Edexcel - GCSE Chemistry - Question 3 - 2016 - Paper 1

Worked Solution & Example Answer:P, Q, R and S are mixtures of food colourings - Edexcel - GCSE Chemistry - Question 3 - 2016 - Paper 1

Which mixture contains an insoluble food colouring?

Give a change that could be made to the experiment to obtain an Rf value for the insoluble colouring.

Explain, by referring to Figure 4, which mixture is separated into the greatest number of soluble food colourings by this chromatography experiment.

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