Thin-layer chromatography
Cambridge A-Level Chemistry (9701) · Unit 37: Analytical techniques (A Level) · 10 flashcards
Thin-layer chromatography is topic 37.1 in the Cambridge A-Level Chemistry (9701) syllabus , positioned in Unit 37 — Analytical techniques (A Level) . In one line: The stationary phase is the solid material on which the separation occurs in TLC. It is typically a thin layer of a substance like aluminium oxide (Al₂O₃) or silica gel supported on a glass or plastic plate.
Marked as A2 Level: examined at A Level in Paper 4 (A Level Structured Questions) and Paper 5 (Planning, Analysis and Evaluation). It is not tested on the AS-only papers (Papers 1, 2 and 3).
The deck below contains 10 flashcards — 6 definitions and 4 key concepts — covering the precise wording mark schemes reward. Use the 6 definition cards to lock down command-word answers (define, state), then move on to the concept and calculation cards to handle explain, describe, calculate and compare questions.
The term 'stationary phase' in the context of thin-layer chromatography (TLC). Give an example
The stationary phase is the solid material on which the separation occurs in TLC. It is typically a thin layer of a substance like aluminium oxide (Al₂O₃) or silica gel supported on a glass or plastic plate.
What the Cambridge 9701 syllabus says
Official 2025-2027 spec · A2 LevelThese are the exact learning outcomes Cambridge sets for this topic. The candidate is expected to be able to do each of these on the relevant paper.
- describe and understand the terms (a) stationary phase, for example aluminium oxide (on a solid support) (b) mobile phase; a polar or non-polar solvent (c) Rf value (d) solvent front and baseline
- interpret Rf values
- explain the differences in Rf values in terms of interaction with the stationary phase and of relative solubility in the mobile phase
- describe and understand the terms (a) stationary phase; a high boiling point non-polar liquid (on a solid support) (b) mobile phase; an unreactive gas (c) retention time
- interpret gas / liquid chromatograms in terms of the percentage composition of a mixture
- explain retention times in terms of interaction with the stationary phase
- analyse and interpret a carbon-13 NMR spectrum of a simple molecule to deduce: (a) the different environments of the carbon atoms present (b) the possible structures for the molecule
- predict or explain the number of peaks in a carbon-13 NMR spectrum for a given molecule
- analyse and interpret a proton (1H) NMR spectrum of a simple molecule to deduce: (a) the different environments of proton present using chemical shift values (b) the relative numbers of each type of proton present from relative peak areas (c) the number of equivalent protons on the carbon atom adjacent to the one to which the given proton is attached from the splitting pattern, using the n + 1 rule (limited to singlet, doublet, triplet, quartet and multiplet) (d) the possible structures for the molecule
- predict the chemical shifts and splitting patterns of the protons in a given molecule
- describe the use of tetramethylsilane, TMS, as the standard for chemical shift measurements
- state the need for deuterated solvents, e.g. CDCl ₃, when obtaining a proton NMR spectrum
- describe the identification of O–H and N–H protons by proton exchange using D₂O
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 9701 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Define the term 'stationary phase' in the context of thin-layer chromatography (TLC). Give an example.
The stationary phase is the solid material on which the separation occurs in TLC. It is typically a thin layer of a substance like aluminium oxide (Al₂O₃) or silica gel supported on a glass or plastic plate.
Define the term 'mobile phase' in the context of thin-layer chromatography (TLC). What is its role?
The mobile phase is the solvent that moves through the stationary phase in TLC, carrying the compounds to be separated. Its polarity influences the relative solubility and movement of different compounds.
Define the Rf value in thin-layer chromatography (TLC).
The Rf value (retardation factor) is the ratio of the distance traveled by the compound to the distance traveled by the solvent front in TLC. Rf = (distance traveled by compound) / (distance traveled by solvent front).
Explain how the interaction with the stationary phase affects the Rf value of a compound in TLC.
Stronger interactions with the stationary phase result in a smaller Rf value, as the compound spends more time adsorbed to the stationary phase and travels a shorter distance up the plate. Weaker interactions lead to higher Rf values.
Explain how the relative solubility of a compound in the mobile phase affects its Rf value in TLC.
Greater solubility in the mobile phase leads to a larger Rf value. The compound is more readily dissolved and carried further up the TLC plate by the solvent.
Describe the stationary phase in gas-liquid chromatography (GLC).
In GLC, the stationary phase is a high-boiling point, non-polar liquid coated on an inert solid support (
Describe the mobile phase in gas-liquid chromatography (GLC).
The mobile phase in GLC is an unreactive carrier gas, such as helium or nitrogen. It's role is to transport the vaporized sample through the column without interacting with it.
Define 'retention time' in gas-liquid chromatography (GLC).
Retention time is the time it takes for a particular compound to travel from the injection point to the detector in GLC. It is used to identify compounds.
How can you interpret a gas/liquid chromatogram to determine the percentage composition of a mixture?
The area under each peak in a GLC chromatogram is proportional to the amount of that component in the mixture. The percentage composition is determined by calculating the percentage of each peak area relative to the total area of all peaks.
Explain how interaction with the stationary phase affects retention times in gas-liquid chromatography (GLC).
Compounds with stronger interactions with the stationary phase will have longer retention times, as they spend more time dissolved in the liquid phase and are therefore slower to pass through the column. Weaker interactions result in shorter retention times.
More Chemistry flashcards
Browse every 9701 flashcard topic by syllabus area.
All Chemistry FlashcardsKey terms covered in this Thin-layer chromatography deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
How to study this Thin-layer chromatography deck
Start in Study Mode, attempt each card before flipping, then rate Hard, Okay or Easy. Cards you rate Hard come back within a day; cards you rate Easy push out to weeks. Your progress is saved in your browser, so come back daily for 5–10 minute reviews until every card reads Mastered.
Study Mode
Rate each card Hard, Okay, or Easy after flipping.