Paper Chromatography: AQA Required Practical

AQA GCSE Chemistry paper chromatography required practical with step-by-step visuals, a 6-mark exam question and Rf calculations. Combined & Triple Science.

We have three different coloured inks (red, yellow and orange).

Plan an experiment to analyse them using paper chromatography and calculate their Rf values.

[6 marks]

• How do we prepare the chromatography paper?

  • Draw a straight line 1 cm up using a pencil

  • Drip ink dots on the line using a pipette

• How do we let the ink run?

  • Support the paper using a pencil and paper clip

  • Insert it into the beaker of water

  • Ensure ink dots are above the water level

  • Allow solvent (water) to rise up the paper

• What do we do after taking it out?

  • Take it out before water runs to the top

  • Immediately, mark the level the water reached (solvent front) before it evaporates

  • Let it dry

  NOTE: water is solvent, dissolved dyes are solutes

• How do we calculate Rf?

  Using a ruler:

  • Measure the distance the dot travelled from the pencil line

  • Measure the distance the water travelled from the pencil line

  Calculate:

  • Rf = solute distance / solvent distance

Challenge:

• How can we identify the dyes using Rf values?

  Compare the calculated Rf values with reference Rf values for known dyes, measured under the same conditions.

• Why do we use pencil, not pen?

  Pencil does not dissolve (is insoluble) in the solvent, so it won't interfere with the results.

• Why do we ensure ink dots are above water level?

  Otherwise, the ink may dissolve directly into the solvent instead of travelling up the paper.

Continue Revising Paper 2

Need help improving your GCSE Chemistry grade?

These visuals are created by our experienced GCSE tutors. Want personalised support?