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P, Q, R and S are mixtures of food colourings - Edexcel - GCSE Chemistry Combined Science - Question 2 - 2016 - Paper 1
Question 2
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 Combined Science - Question 2 - 2016 - Paper 1
Step 1
Which mixture contains an insoluble food colouring?
Answer
Based on the chromatogram shown in Figure 4, the mixture that contains an insoluble food colouring is mixture R. This is because the spot corresponding to mixture R does not move up the paper, indicating that it did not dissolve in the solvent used and is therefore insoluble.
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, a change that could be made is to use a different solvent that is more suitable for dissolving the specific food colouring present in the mixture. Additionally, one could try applying heat to help dissolve the colouring in the solvent, if appropriate.