12.4 Separation and purification
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19. Describe the five methods of separation and purification listed in the syllabus.
- Use of a suitable solvent: Dissolves only one specific soluble component out of a solid mixture.
- Filtration: Separates an insoluble solid from a liquid suspension.
- Crystallisation: Obtains pure crystals of a solute from a hot, saturated solution by cooling.
- Simple distillation: Separates a volatile liquid solvent from a non-volatile dissolved solute.
- Fractional distillation: Separates a mixture of miscible liquids with close but distinct boiling points using a fractionating column.
20. How do you choose a suitable separation or purification technique for a specific mixture?
By analyzing structural properties and constants such as state data, solubility values, melting thresholds, and physical boiling configurations of each chemical.
21. How can the purity of a substance be assessed using physical data?
By testing and measuring its precise thermal profile. Pure substances possess highly unique, sharp, discrete melting and boiling points, whereas contamination depresses melting profiles and broadens boiling lines.