• itunuoluwa oladipupo separating techniques
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    pls outline the processes involved in all separating techniques     08 September 2010Comment
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    • ehiremen isaiah U need to consult a textbook, bcos the process are much.
      Like It0 Unlike It0 10 September 2010
    • andy chuks Some Separation Techniques and brief processes involved

      - Filtration

      A solid which has not dissolved in a liquid can be separated by filtration.
      A filter paper is placed inside a glass funnel and a container put beneath.
      The mixture is poured in through the filter paper
      The solid remaining in the filter paper is called the residue.
      The residue can be dried by spreading it out on the filter paper and allowing the liquid to evaporate.
      The liquid which has passed through the filter paper is called the filtrate


      - Crystallisation.

      A solid which has dissolved in a liquid (called a solution) can be separated by crystallisation.
      The dissolved substance is called the solute.
      The liquid used for dissolving is called the solvent.
      The solution is warmed in an open container, allowing the solvent to evaporate, leaving a saturated solution.
      A solution which has as much solid dissolved in it as it can possibly contain, is called a saturated solution.

      As the saturated solution is allowed to cool, the solid will come out of the solution and crystals will start to grow.
      The crystals can then be collected and allowed to dry.



      - Distillation
      A liquid can be separated from a mixture of liquids in a solution by fractional distillation.
      The solution is heated until it boils.
      The liquid with the lowest boiling point boils first and becomes a vapour (gas).
      The vapour is cooled in the condenser until the temperature falls below the boiling point when it condenses back into a liquid which is collected in a container.
      The collected liquid is called the distillate. It has been distilled.
      The condenser has cold water running through a jacket around the outside
      to keep the temperature below the boiling point of the vapour.

      After the liquid with the lowest boiling point has been collected,
      the temperature of the remaining mixture will rise to a new temperature
      when the liquid with the next lowest boiling point will boil
      and can be collected. The process can be continued to separate all the liquids
      in the mixture


      - Chromatography
      This technique is used to separate complex mixtures such as ink

      The mixture (eg two green ink spots) is put on a filter paper which is placed in a suitable solvent.

      As the solvent rises up the filter paper the individual dyes within the green ink spots are separated and different dyes travel different distances up the paper.
      The solvent travels furthest up the filter paper leaving a line called the solvent front.


      - Sublimation

      Sublimation is a separation technique used to purify a solid chemical substance. It is commonly called vacuum sublimation because it is usually carried out at low pressures. In sublimation, a solid is heated in a flask under vacuum. This method of heating usually makes the solid sublime directly into a gas without first melting into a liquid. The gas is then condensed on a cold surface, which causes the solid to re-form. Impurities, which are usually of heavier molecular weight and do not evaporate as easily, are left behind on the bottom of the flask. The solid can be scraped off the cold surface for further reactions or analysis.

      Read More Consult a textbook for diagrammatic expression and better understanding
      Like It2 Unlike It0 14 September 2010