How do you separate different components in a mixture?
- by discriminating between components with different properties.
l high / low density
l volatile / nonvolatile
l reactive/ inert
l soluble / insoluble
l magnetic / non magnetic
Note: Separation works because components in a mixture retain their identities. However, it would be more difficult to separate if the properties are similar.
² Filtration: select components by particle size
² Floatation: select components by density
² Crystallization and Extraction: select components by solubility
² Distillation: select components by boiling point
² Chromatography: select components by
Hand Separation (solids + solids)
- a mechanical mixture or heterogeneous mixture
- can be separated by using a magnet or sieve
Evaporation (solid dissolved in liquid solution)
- boil until the liquid evaporates
- solid part remains
Filtration [solids(not dissolved) and liquids]
- separate by passing the mixture through a porous filter
- use filter paper, the residue is left in the paper while filtrate goes through
- precipitation is the conversion of a solute to solid form by physical or chemical change
-solid separated by 1. filtration
2. floatation
-saturated solution of a desired solid
-solid come out as pure crystals, then crystals are separated from the remaining solvent by filtration
Gravity separation
-solid based on different density
-a centrifuge whirls the test tube around at high speed, which forces the denser materials to the bottom
*small volumes works better
Solvent extration
-a component moves into a solvent shaken with the mixture
-solvents that dissolve only one component works better
-mechanical mixture (solid in solid) : use liquid to dissolve one solid , then you get the other one
-solution: solvent dissolves one and leaves unwanted solid behind
Distillation (liquid in liquid)
- heating cause low-boiling component to vaporize first
-collecting and condensing volatilized component
(Vapour ascents to distillation flask and enters condenser)
Chromatography
-The material of the mixture retains some components, different components flow over the material have different speeds.
-The material of the mixture retains some components, different components flow over the material have different speeds.
- A mobile phase sweeps the sample over a stationary phase.
-This can separate very complex mixtures and form of separation uses very small sample sizes and analysis is highly accurate and precise.
Sheet Chromatography
Paper Chromatography (PC) :
-Stationary phase (absorbent) is a liquid soaked into a stripe of paper, mobile phase is a liquid solvent.-different components move at a different speeds. Some components spend more time in the stationary phase. The components appear as separated spots on the paper.
Thin Layer Chromatography (TLC) :
-stationary phase (ex. Al2O3, SiO2) is a thin layer of absorbent.-some components bond to the absorbent strongly, some weakly. ( the speeds of the components)
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