AQA A-Level Chemistry 7405
Atomic Structure
Amount of Substance
Bonding
Energetics and Thermodynamics
Kinetics
Chemical Equilibria
Redox and Electrochemistry
Acids and Bases
Periodicity and Group Chemistry
Period 3 Elements and Their Oxides
Transition Metals
Introduction to Organic Chemistry
Hydrocarbons
Halogenoalkanes, Alcohols and Organic Analysis
Carbonyls, Carboxylic Acids and Derivatives
Aromatic Chemistry and Amines
Polymers, Amino Acids, Proteins and DNA
Organic Synthesis, NMR and Chromatography
Organic Synthesis, NMR and Chromatography
Thin-Layer Chromatography and Rf Values
- 3 things to know
- Papers 2 and 3
Overview
The stationary and mobile phases, calculating Rf, and identifying a spot.
What you need to know
Answer each one before you reveal it.
What is the Rf value?
How is the Rf value calculated?
Questions from this subtopic
Each one with the model answer underneath.
- 1
What is thin-layer chromatography?
Model answer
A chromatographic technique where a plate is coated with a solid stationary phase and a solvent moves up the plate as the mobile phase.
- 2
What is the stationary phase in thin-layer chromatography?
Model answer
A solid coating on the plate.
- 3
What is the mobile phase in thin-layer chromatography?
Model answer
A solvent.
- 4
In which direction does the solvent move in thin-layer chromatography?
Model answer
Upwards.
- 5
What is the Rf value?
Model answer
The retention factor, which is a ratio indicating how far a substance travels relative to the solvent front.
- 6
How is the Rf value calculated?
Model answer
Rf = distance travelled by substance ÷ distance travelled by solvent front.
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