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2.2.10—Chromatography

Syllabus
First assessment 2025
Objective
2.2.10
Level
SL

Chromatography and Rf

Chromatography separates components because they have different attractions to the stationary and mobile phases. A component that is more strongly attracted to the mobile phase travels farther.

the pencil baseline and initial sample are visibly above the solvent level; the chromatogram baseline is 0.0 cm and the spot centres are 2.0, 6.0 and 8.0 cm; the solvent front is exactly 12.0 cm; both measurement arrows begin at the same baseline.

Rf=distancetravelledbycomponent/distancetravelledbysolventfrontRf = distance travelled by component / distance travelled by solvent front

Rf is a dimensionless ratio of distances measured from the same origin under the same conditions. Because a component cannot pass the solvent front, a valid result lies from 0 to 1; a value above 1 signals a distance or origin error. Operational details beyond the separation principle are not assessed here.

If a spot moves 3.2 cm while the solvent front moves 8.0 cm, Rf = 0.40. A larger Rf means greater relative affinity for the mobile phase under those conditions, but values from different solvents, stationary phases or temperatures are not directly interchangeable.

Interpreting Chromatograms

[ 2 ]

Explain how the separation of inks is achieved using paper chromatography.

The Covalent Model Summary

Retrieve the covalent pathway: shared pairs and bond order lead to geometry, polarity and molecular polarity; structure determines network properties, IMF behaviour and chromatography; HL representations extend to resonance, formal charge, sigma/pi bonds and hybridization.

Check the representation first, then count domains, apply geometry, identify polarity or forces, and connect the structure to the requested property or HL bonding description.