O-LevelChemistryBonding & Structure5070/41 · May/June 2023 · Q16 Marks

A student uses chromatography to separate the dyes in a food colouring. Fig. 1.1 shows the apparatus the student uses. [Figure 1.1]

(a)Name apparatus X.[1]
(b)State why it is important to have a lid on X.[1]
(c)State why the start line is: • above the level of the solvent • drawn in pencil. above the level of the solvent drawn in pencil[2]
(d)The R₏ value of one of the dyes in the food colouring is 0.60. In the separation this dye travels 5.7 cm. Calculate the distance travelled by the solvent during the separation. distance travelled by solvent ..................................................... cm[2]

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Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

[1] beaker
[1] prevent evaporation of solvent (from the beaker) OR To ensure the air in the beaker is saturated with vapour
[1] M1 (start line above level of solvent so) dye doesn't dissolve off paper into solvent
[1] M2 (start line in pencil so) line doesn't smudge / smear / travel up paper (start line in pencil as) pencil does not dissolve / pencil is insoluble
[1] M1 5.7/0.6
[1] M2 9.5 cm

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