Paper Chromatography
Introduction
- Paper chromatography is a technique used to separate substances based on solubility.
- It's useful for identifying components in mixtures, such as colors in inks.
Separation Techniques
- Other separation techniques:
- Filtration
- Crystallization
- Distillation (simple and fractional)
- Chromatography is another key technique.
How Paper Chromatography Works
Materials
- Chromatography Paper: Special paper used for the process.
- Solvent: Liquid that dissolves substances.
Procedure
- Draw a pencil line near the bottom of the chromatography paper.
- Place dots of different colors on the pencil line.
- Place the bottom of the paper into a solvent.
- The solvent moves up the paper, carrying the ink with it.
Key Concepts
- Stationary Phase: Chromatography paper (does not move).
- Mobile Phase: Solvent (moves up the paper).
Interpreting Results
- Pure Substance: Produces a single spot.
- Mixture: Separates into multiple spots.
- Different substances travel different distances based on solubility.
Example
- Red Color: Forms a single spot (pure).
- Color B: Separates into two spots (mixture).
Practical Application
Identifying Unknown Substances
- Dot of unknown chemical placed on pencil line.
- Measure distance moved by chemical and by solvent.
Calculating RF Value
- RF Value: Distance moved by substance / Distance moved by solvent.
- Example: Substance moved 44mm, solvent moved 75mm.
- RF Value = 44mm / 75mm = 0.57
- RF values are unitless.
- Look up RF value in a database to identify the substance.
Considerations
- Repeat with different solvents for accuracy.
- New substances might require additional analyses.
Additional Resources
- More questions and revision materials are available in the workbook linked in the lecture.
By understanding these concepts and procedures, one can effectively use paper chromatography to identify unknown substances in mixtures.