Fractional Distillation


 
 
Concept Explanation
 

Fractional Distillation

This method is used to separate the components of a mixture of two or more miscible liquids whose boiling points differ by 25°C or less.

For example, methyl alcohol (boiling point 65°C) can be separated from acetone (boiling point 56°C) by this method. The mixture is heated in a round-bottomed flask over a sand bath. The flask is attached to a fractionating column. The fractionating column has several traps to allow the higher boiling liquid (less volatile) to condense. The vapour of lower boiling liquid (more volatile) goes into the condenser where it is condensed and the liquid thus obtained is then collected in the receiver. The temperature remains fixed at the boiling point of the lower-boiling liquid. When this more volatile liquid is completely distilled, the temperature rises to the boiling point of the next higher-boiling liquid. This liquid is collected in another receiver. In this way, all the components of the mixture can be separated.

This method is adopted to separate the various components of petroleum

  • The apparatus is similar to that for simple distillation, except that a fractionating column is fitted in between the distillation flask and the condenser.
  • A simple fractionating column is a tube packed with glass beads. The beads provide surface for the vapours to cool and condense repeatedly.
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    Sample Questions
    (More Questions for each concept available in Login)
    Question : 1

    Fractional Distillation method is used to separate the components of a mixture of two or more miscible liquids whose boiling points differ by__________________________.

    Right Option : A
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    Explanation
    Question : 2

    In fractional distillation of air, which of the following gases is separated first?

    Right Option : C
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    Explanation
    Question : 3

    A mixture of methyl alcohol and acetone can be separated by

    Right Option : B
    View Explanation
    Explanation
     
     
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