Separation of Mixtures Flashcards
(6 cards)
Describe the method of paper chromatography
1) Take a piece of chromatography paper and draw a pencil line near the bottom, add the coloured dots to the pencil line.
2) Place the bottom of the paper into a solvent which will move up the paper dissolving the ink in the dots.
3) Ink is carried up the paper dissolved in the solvent.
4) Look at how many coloured dots are left from the solvent.
We call the paper the stationary phase and the solvent the mobile phase
Describe the method of simple distillation.
1) Add the liquid and dissolved solid to the flask and heat the solution.
2) The liquid starts to evaporate turning into a vapour which rises up the glass tube passing over the thermometer increasing the reading. ( usually heat till boils)
3) Next the vapour passes into the condenser ( Cold from tap water circulating)
4) This causes the water vapour to condense turning back into a liquid collected in the beaker.
At the end left with crystals of the solid in the flask and liquid in the beaker.
Describe the method of simple distillation.
1) Add the liquid and dissolved solid to the flask and heat the solution.
2) The liquid starts to evaporate turning into a vapour which rises up the glass tube passing over the thermometer increasing the reading. ( usually heat till boils)
3) Next the vapour passes into the condenser ( Cold from tap water circulating)
4) This causes the water vapour to condense turning back into a liquid collected in the beaker.
At the end left with crystals of the solid in the flask and liquid in the beaker.
Outline the process of fractional distillation.
Separating a mixture of different liquids but MUST have different boiling points.
1) Heat the solution to evaporate the liquid turning it into a vapour.
2) Cool the vapour to condense it back to a liquid.
Describe the method of fractional distillation.
1) Gently heat the mixture, both liquids will start to evaporate, but the one with the lower boiling point will evaporate more easily.
2)When both vapours reach the fractionating column they condense and drip back into the flask, where they evaporate again.
3) This repeated evaporation and condensation increases the amount of the lower boiling point in the fractionating column.
4) Lower point moves up the fractioning column ahead of HBP, they reach the thermometer rising the temperature - mixture of two different vapours passing over, contains more of LBP.
5) Vapours pass into condenser turning back to liquid - ixture of two chemicals.
6) when temp stops rising there is main,y one chemical passing to condenser to be collected in a fresh beaker.
7) Temp rises again this mixture is mainly HBP,when reaches a constant temp we are collecting the HBP liquid.
What may cause issues with fractional distillation.
1) Liquids having similar boiling points - harder to separate, may need several rounds.
2) Not usual for a very large volume - crude oil.
