Paper chromatography — final check

1. Explain

A pupil draws an ink baseline 10 mm above the paper bottom. Solvent is 15 mm deep. They plan to mark the front after drying. Explain all three faults. Describe a fresh setup and finishing sequence that avoids them.

Prepare the paper and solvent, with reasons

Develop and finish in order

Explain the key precautions

2. Explain

On one paper, Z gives violet spots 18 mm and 42 mm from the baseline. P gives one at 18 mm; Q gives one at 30 mm. Interpret Z and its matches. Another sample gives one spot. State the purity conclusion that result supports, including its limit.

3. Calculate

A colourless paper is removed, its wet front marked, then dried and located. Spot centres are 30 mm and 54 mm above the bottom edge. Baseline and front are 6 mm and 66 mm above it. Calculate both Rf values and interpret the spots. Explain what would be lost without the front mark. Describe when a locating agent is used and how its role differs from the solvent.

Calculations

Interpretation and missing-front consequence

Locating method and its difference from the solvent