Lesson 3.3.16

3.3.16 Chromatography Quiz: AQA Chemistry, Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.3.16, Chromatography: 20 multiple choice questions for the AQA Chemistry (7405), Unit 3: Organic chemistry, written with Revision Ninja.

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The 20 questions

  1. What is the purpose of chromatography?

    • To separate and identify the components of a mixture
    • To measure the density of a liquid
    • To make new compounds from elements
    • To count the number of atoms in a molecule

  2. In thin-layer chromatography, what is coated on the plate?

    • A solid stationary phase
    • A liquid that moves up the plate
    • A metal electrode
    • A gas under pressure

  3. In column chromatography, how does the solvent move?

    • Down the column, through a solid packed inside
    • In a gas stream at high temperature
    • Through a membrane with an electric field
    • Up the column by capillary action only

  4. What is the mobile phase in gas chromatography?

    • A solid that moves down the column
    • A liquid solvent that dissolves the sample completely
    • A gas passed through the column under pressure at high temperature
    • A supercritical fluid in a sealed tube

  5. What determines how well a component separates in chromatography?

    • The balance between its solubility in the moving phase and its retention by the stationary phase
    • The colour of the sample only, which decides how far each spot travels
    • The temperature of the laboratory only, which changes the solvent front speed
    • The molar mass only, which is the single factor that controls the separation

  6. What is the Rf value of a spot that moves 2.5 cm when the solvent front moves 5.0 cm?

    • 0.25
    • 0.5
    • 7.5
    • 2.0

  7. A spot moves 4.2 cm and the solvent front moves 7.0 cm. What is the Rf value?

    • 0.60
    • 1.67
    • 0.40
    • 0.33

  8. How are unknown components identified in gas chromatography?

    • By measuring their colour in the column as they pass through the stationary phase
    • By counting the number of peaks only, without comparing any retention times at all
    • By comparing their retention times with those of known standards under the same conditions
    • By weighing the column before and after the separation to find the mass moved

  9. What does GC-MS do?

    • It separates the mixture by gas chromatography and identifies each component by mass spectrometry
    • It separates ions using only magnetic fields, with no solvent or gas stream needed
    • It titrates each component with a base as it elutes from the column in sequence
    • It measures the NMR spectrum of each liquid as it leaves the column one by one

  10. Which technique is used to identify transition metal ions in solution in the specification?

    • Thin-layer chromatography
    • Infrared spectroscopy only
    • Mass spectrometry only
    • Titration with sodium hydroxide

  11. Which compound's Rf value would be higher on the same TLC plate with the same solvent?

    • The compound that is more soluble in the moving solvent and less retained by the stationary phase
    • The compound with the greater molar mass always, regardless of the solvent used
    • The compound that absorbs more infrared radiation and so travels further up the plate
    • The compound that is less soluble and strongly retained by the solid support

  12. Why does a longer retention time suggest a stronger retention by the stationary phase?

    • The component is more volatile, so it condenses faster on the column walls
    • The component spends more time held on the stationary phase before it moves through the column
    • The component reacts with the carrier gas, which slows it down in the column
    • The component has a lower molar mass, so it is held more strongly in the column

  13. Why must colourless compounds on a TLC plate be visualised by a developing agent or UV light?

    • Colourless compounds are gases on the plate, so they escape before they can be seen
    • The developing agent makes the compounds separate, so no separate visualisation is needed
    • Their spots are not visible by eye, so a developing agent or UV light is needed to show their positions
    • Colourless compounds always dissolve in the solvent, so they cannot be seen on the plate

  14. Which technique would best separate a volatile mixture of alkanes?

    • Gas chromatography
    • Thin-layer chromatography on silica
    • Titration
    • Recrystallisation

  15. What should be concluded if two components give identical retention times under the same GC conditions?

    • They must be different compounds with identical masses, since the retention times match
    • The components are optically inactive, so they must be the same compound
    • The column has failed completely, so the separation has not worked at all
    • They may be the same compound, so mass spectrometry should be used to confirm

  16. Which application of TLC is named in the specification for analgesics?

    • Measuring the melting point of aspirin
    • Identifying analgesics
    • Determining the molecular formula of analgesics
    • Titrating aspirin with sodium hydroxide

  17. In column chromatography, which component elutes first from the column?

    • The one with the highest molar mass always, since heavier molecules leave last
    • The one that reacts with the solid, which is then held back in the column
    • The one most strongly retained by the solid, which is slowest to leave the column
    • The one least retained by the solid and most soluble in the solvent

  18. What is the purpose of Required practical 12?

    • To separate species by thin-layer chromatography
    • To titrate a weak acid with a strong base
    • To prepare a pure organic solid by recrystallisation
    • To measure the enthalpy of combustion of an alcohol

  19. What is the main difference between the stationary phases in TLC and GC?

    • TLC uses a gas stationary phase, while GC uses a solid plate for separation
    • TLC uses a liquid only, while GC uses a metal wire coated with a solid for the separation
    • TLC uses a solid stationary phase on a plate, while GC uses a solid or liquid-coated solid inside a column
    • Both use the same stationary phase in the same way, so the techniques differ only in the solvent

  20. Which statement about Rf values is correct?

    • Rf values can be greater than 10 for most compounds, since the solvent front is short
    • Rf values depend only on the colour of the spot, which determines how far it travels
    • Rf values lie between 0 and 1 because the spot cannot travel further than the solvent front
    • Rf values are always negative, because the spot moves against the direction of solvent flow

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