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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?
Answer
The insoluble food colouring is indicated by the absence of a spot's movement from its original position along the chromatography paper. In Figure 4, mixture S has no visible spot, indicating it contains the insoluble food colouring.
Step 2
Give a change that could be made to the experiment to obtain an Rf value for the insoluble colouring.
Answer
To obtain an Rf value for the insoluble colouring, the chromatography solvent could be changed to something more suitable that may solubilize the colouring, or a different method such as dissolving the sample in a solvent before chromatography could be employed.
Step 3
Explain, by referring to Figure 4, which mixture is separated into the greatest number of soluble food colourings by this chromatography experiment.
Answer
Referring to Figure 4, mixture P displays the highest number of distinct spots compared to other mixtures. This indicates that it is separated into the greatest number of soluble food colourings, as each spot represents a different soluble component in the mixture.