9 End-of-chapter test
Chromatography
1
The gas–liquid chromatogram for a mixture of organic compounds is shown below.
a
b
c
d
e
f
g
Give the correct labels for A, B and C.
What percentage of the mixture is pentan-1-ol?
Give an explanation for the different retention times.
i How would the chromatogram change if the liquid in the stationary phase was
more polar?
ii Explain your answer.
Why is gas–liquid chromatography useful in testing for anabolic steroids in the blood of
athletes?
Explain why the use of gas–liquid chromatography linked to a mass spectrometer is
so useful.
Why is it difficult to separate dyes using gas–liquid chromatography?
COAS Chemistry 2 Teacher Resources
Original material © Cambridge University Press 2005, 2007, 2009
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9 End-of-chapter test
2
Paper chromatography was used to separate a mixture of amino acids. The mixture was run in
two dimensions using two different solvents. The chromatogram obtained is shown below.
a
b
c
d
e
Explain briefly how the chromatography was carried out.
Which amino acids were inseparable using solvent 1? (Give just the corresponding letters.)
How could the amino acids be located?
Give the Rf value for amino acid C in each solvent.
In another experiment, a mixture of radioactively labelled amino acids was separated
using paper chromatography. The following results were obtained.
[4]
[2]
[1]
[2]
i Find the Rf values for acids X, Y and Z. Show your working.
[3]
ii Measure the area under each peak and find the percentage composition of the mixture. [4]
iii Explain how paper chromatography is used to separate the components of a mixture.
[4]
Total:
COAS Chemistry 2 Teacher Resources
41
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Original material © Cambridge University Press 2005, 2007, 2009
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