A student investigated the colours in three different flowers, A, B and C - AQA - GCSE Chemistry - Question 4 - 2018 - Paper 2
Question 4
A student investigated the colours in three different flowers, A, B and C.
The colours are soluble in ethanol but are insoluble in water.
This is the method used.
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Worked Solution & Example Answer:A student investigated the colours in three different flowers, A, B and C - AQA - GCSE Chemistry - Question 4 - 2018 - Paper 2
Step 1
Mistake 1
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Answer
The start line was drawn in ink instead of pencil. This would lead to the ink dissolving in the solvent, affecting the results.
Step 2
Mistake 2
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Answer
Water was used instead of ethanol as the solvent. This would mean the colours cannot dissolve or move on the chromatography paper.
Step 3
Conclusions from Figure 5
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Answer
The flowers do not share any common colours.
Flower A contains one colour while flower C contains two colours.
Step 4
Calculate the distance moved by the solvent
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Answer
Using the formula for Rf value:
Rf=distancemovedbysolventdistancemovedbysubstance
Substituting the known values:
0.65=distancemovedbysolvent3.2
Solving for the distance moved by solvent:
distancemovedbysolvent=0.653.2=4.923076923cm
