Separation of mixtures
3 marks · EasyA student carries out chromatography to separate the dyes in two different food colourings, X and Y. The chromatogram below shows the results. Each spot represents a dye.
How many different dyes are present in colouring X?
Which dye(s) are found in both X and Y?
Suggest why one dye in X reached the top of the chromatogram while another travelled only a short distance.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
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(a) 3
(b) Dyes at 2 cm and 9 cm
(c) The dye that reached the top is more soluble in the solvent or less attracted to the paper; the dye that travelled only a short distance is less soluble or more attracted to the paper.
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly states X contains 3 different dyes (uses number of spots for X)
B1 (b) · 1 mark · Identifies that the spots at 2 cm and 9 cm are present in both X and Y.
B1 (c) · 1 mark · States that dyes travel distances depending on solubility in the solvent or attraction to the paper.
Worked solution
(a) There are three spots in X so there are 3 different dyes in colouring X.
(b) Both X and Y have spots at 2 cm and 9 cm, so these dyes are present in both.
(c) The dye that reached the top is more soluble in the solvent or less strongly attracted to the paper. The dye that moved only a little is less soluble or more strongly attracted to the paper.