AQA · Chemistry · 8462

GCSE Chemistry: Chromatography

Chemical analysis · AQA GCSE Chemistry (8462), specification point 4.8.1.3. Cards are generated from the exam board's own specification for "Chromatography", and every card links back to the page it came from. Specification © AQA — used with attribution.

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  1. What are the two phases involved in chromatography?

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    A stationary phase and a mobile phase.

  2. What does separation in chromatography depend on?

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    The distribution of substances between the stationary phase and the mobile phase.

  3. What is the formula for calculating an Rf value?

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    Rf = distance moved by substance ÷ distance moved by solvent.

  4. From where to where is the distance moved by a compound measured when finding its Rf value?

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    From the origin (baseline) to the centre of the spot.

  5. In paper chromatography, the ? phase is the solvent that moves up the paper.

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    mobile

  6. Why can Rf values help identify a compound?

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    Different compounds have different Rf values in a given solvent, so a measured Rf can be matched against known values.

  7. How does a chromatogram show that a substance is pure?

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    A pure compound produces a single spot in all solvents.

  8. How does a chromatogram show that a substance is a mixture?

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    The mixture separates into more than one spot (depending on the solvent used).

  9. A pure compound produces a ? spot on a chromatogram in all solvents.

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    single

  10. What is the maximum possible Rf value, and why?

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    1 — a substance cannot travel further than the solvent front that carries it.

  11. What does AQA GCSE Chemistry Required Practical 6 investigate?

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    Using paper chromatography to separate and distinguish coloured substances, including calculating Rf values.

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