Chromatography (A-level only) (AQA A Level Chemistry)

Exam Questions

2 hours30 questions
11 mark

TLC stands for

  • Travelling liquid chromatograph

  • Transitioning liquid chromatography

  • Transition layer chromatography

  • Thin-layer chromatography

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21 mark

In thin-layer chromatography, which of the following can not be used to “locate” spots for colourless compounds?

  • Iodine vapour

  • Methyl orange

  • Ninhydrin

  • Ultraviolet light

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31 mark

A suitable carrier gas for use in gas-liquid chromatography is

  • Carbon dioxide

  • Chlorine

  • Nitrogen

  • Oxygen

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41 mark

A chromatogram showing the separation of a mixture of amino acids is shown.

7-11-e-q4-mcq-aqa-al-chemistry



A = Lysine 

B = Serine

C = Histidine

D = Tyrosine 

E = Isoleucine

F = Methionine

Which amino acid is the most soluble?

  • Isoleucine

  • Lysine

  • Methionine

  • Tyrosine

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51 mark

In chromatography, which of the following can be the mobile phase?

  • Liquid only

  • Liquid or gas

  • Solid or liquid

  • Gas only

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11 mark

A chromatogram of two compounds, A and B, is shown.

7-11-m-q1-mcq-aqa-al-chemistry

The Rf value of compound B is

  • 0.21

  • 0.44

  • 0.65

  • 1.54

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21 mark

The distance that an individual amino acid moves on a chromatogram depends on

  • The intermolecular forces between the amino acid and the stationary phase

  • The intermolecular forces between the amino acid and both the mobile and stationary phases

  • The intermolecular forces between the solvent and the stationary phase

  • The intermolecular forces between the solvent and both the mobile and stationary phases

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31 mark

In gas-liquid chromatography, gaseous samples pass through a long tube containing a liquid stationary phase.

The mixtures in the samples are separated into their components due to their

  • Force of attraction to the liquid

  • Force of attraction to the solid

  • Relative molecular mass

  • Volatility

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41 mark

Which of the following do components with a high Rf value have a greater affinity for?

  • No phase

  • The mobile phase

  • The stationary phase

  • The latent phase

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51 mark

Which of the following statements are correct for gas-liquid chromatography?

 

 

Components can be identified by their retention time

The relative peak area gives the proportion of each component

Calibration curves are used to compare component concentrations

A

X

X

B

X

C

X

D

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    11 mark

    A tripeptide was hydrolysed and then analysed using thin-layer chromatography.

     7-11-h-q1-aqa-al-chemistry

     

    A = Lysine

    B = Serine

    C = Histidine

    D = Tyrosine

    E = Isoleucine

    F = Methionine

    G = Proline

    H = Hydrolysed tripeptide

     

    Using the information, which conclusion is correct?

    • The tripeptide is ser-tyr-met

    • The tripeptide contains mostly serine

    • The TLC needs to be run again using a different solvent

    • The tripeptide contains serine, tyrosine and methionine

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    21 mark

    A sample of cyclohexene contaminated with cyclohexanol is separated by column chromatography.

    Hexane is used as the mobile phase and silica gel as the stationary phase.

    Which statement correctly explains why cyclohexene has a shorter retention time than cyclohexanol?

    • Cyclohexene and cyclohexanol have different polarities

    • Cyclohexene is polar due to the C=C

    • Cyclohexanol is held in the mobile phase for longer

    • Cyclohexanol can form hydrogen bonds with the silica gel

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    31 mark

    The dipeptide cysteine-serine (cys-ser) and the dipeptide serine-cysteine (ser-cys) are shown.

    7-11-h-q3-aqa-al-chemistry 

    Gas chromatography followed by mass spectrometry (GC-MS) is used to analyse a mixture of the two dipeptides.

    Which statement about the analysis of the two dipeptides is correct?

    • Gas chromatography is unable to separate the two dipeptides

    • Cys-ser will have a greater retention time than ser-cys

    • Mass spectrometry is unable to distinguish between the dipeptides

    • The two dipeptides have the same relative affinity for the mobile and stationary phases

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    41 mark

    A student spotted samples of 1,2-dinitrobenzene, 1,3-dinitrobenzene and 1,4-dinitrobenzene on a silica gel TLC plate.

    The solvent that the student used to run the TLC experiment was hexane.

    The student calculated the Rf values for 1,2-dinitrobenzene and 1,4-dinitrobenzene.

     

    Compound

    Rf value

    1,2-dinitrobenzene

    0.36

    1,3-dinitrobenzene

     

    1,4-dinitrobenzene

    0.74

     

    What could the Rf value for 1,3-dinitrobenzene be?

    • 0.80

    • 0.55

    • 0.45

    • 0.30

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    51 mark

    Zineb is a chemical that is used in agriculture as a fungicide. It is less toxic than other fungicides containing copper(II) compounds and it has a low solubility in water.

     7-11-h-q5a-aqa-al-chemistry

     

    Recently, Zineb has been discontinued in many countries as one of its breakdown products is the highly water soluble compound ethylene thiourea (ETU). 

     7-11-h-q5b-aqa-al-chemistry

     

    ETU has been found to be carcinogenic, mutagenic and reproductively toxic.

     

    Chromatography can be used to detect small quantities of ETU in Zineb.

     

    Which statement about the analysis of ETU and Zineb is correct?

    • Gas-liquid chromatography is the most appropriate method of chromatography to separate ETU and Zineb

    • With a silica stationary phase and a water mobile phase, ETU has a higher Rf value than Zineb

    • With a silica stationary phase and a water mobile phase, ETU has a higher retention time than Zineb

    • Zineb has a greater affinity for the water mobile phase than ETU

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