A student investigated the colours in a brown ink using chromatography - AQA - GCSE Chemistry Combined Science - Question 1 - 2022 - Paper 2
Question 1
A student investigated the colours in a brown ink using chromatography.
Figure 1 shows the apparatus used.
Give two errors made by the student.
Describe the probl... show full transcript
Worked Solution & Example Answer:A student investigated the colours in a brown ink using chromatography - AQA - GCSE Chemistry Combined Science - Question 1 - 2022 - Paper 2
Step 1
Give two errors made by the student. Describe the problem each error would cause.
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Answer
Error 1: The student drew the start line in ink instead of using a pencil.
Problem 1: If the start line is drawn in ink, it may dissolve in the solvent, leading to unclear results as the ink will mix with the solvent, causing inaccurate measurements.
Error 2: The solvent was placed above the start line.
Problem 2: If the solvent is above the start line, it can dissolve the colours before the experiment begins, resulting in potential mixing and incorrect distances travelled by the colours.
Step 2
Give two conclusions the student can make from Figure 2 about the four colours in the brown ink.
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Answer
The brown ink contains blue, yellow, and red colours, but no green colour.
The blue colour is likely the most soluble since it travelled the furthest distance in comparison to the other colours.
Step 3
Why was the green colour still on the start line at the end of the experiment?
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Answer
The green colour was insoluble in the solvent.
Step 4
Calculate the distance the solvent moved.
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Answer
Using the Rf equation:
Rf=distancemovedbysolventdistancemovedbycolour
Substituting the values:
0.24=distancemovedbysolvent1.8cm
Rearranging gives:
distance moved by solvent = \frac{1.8cm}{0.24} = 7.5cm.
