Separation of Mixtures: Methods, Solubility and Colligative Properties
Separation of mixtures:
- Mechanical: (forces)
- Sedimentation: The process consists of letting the substances stand for a sufficient time so that the solid particles fall to the bottom in layers, after which the upper part is separated.
- Decantation: Similar to sedimentation, but used with liquids of different density.
- Centrifugation: This is based on the same principles as the previous ones, using centrifugal force to clarify liquids.
- Levigation: Uses a stream of water whose density is greater than that of the substances to be separated.
- Filtering: Separates the liquid from the solid particles by means of sieves (filters, ceramic, etc.).
- Magnetic: Uses magnetic forces to separate ferrous metals from other substances.
- Chromatography: The aim is to drag the mixture of dissolved substances through a solid solute by means of a solvent that moves by capillarity. Each substance has a different velocity, so they separate.
- Thermal: (heat)
- Crystallization: The process consists of evaporating water using a crystallizer (a basin with a wide base and low edges).
- Evaporation to dryness: The solution is heated in a pot, obtaining a powdered substance.
- Distillation: Heating a mixture of several liquids until one of them reaches its boiling point, then keeping the temperature stable until that liquid has evaporated.
- Fractional distillation: The mixture is studied in a tower-shaped apparatus heated to about 400 ºC, so that its components boil at different heights. When the vapors reach the height corresponding to their boiling temperature, they condense and liquefy.
Solubility:
Solubility: The maximum quantity of a substance that can dissolve in 100 g of solvent at a given temperature.
Dilute: The solute quantity is very small with respect to the solubility.
Concentrated: The quantity of solute is close to its solubility.
Saturated: The solution does not admit any more solute.
The factors that influence solubility are:
- The nature of the substances of the solution
- Temperature
Colligative properties:
Cryoscopy: The decrease in freezing temperature is proportional to the number of solute particles dissolved in the solvent.
Ebullioscopy: The increase in boiling temperature is proportional to the number of solute particles present.
Osmosis: The phenomenon in which solvent particles pass through a semipermeable membrane from the region of lower solute concentration to the region of higher concentration.