what is the criteria for fractional distillation?

Asked by SHERIL SINGH | 18th Aug, 2010, 04:04: PM

Expert Answer:

Fractional distillation is done to seprate 2 or miscible liquids for which difference in boiling point is less than  25 K
  • The mixture of two or more liquids with different boiling points is heated to a high temperature..
  • The mixture boils, forming vapor
  • The vapor enters the bottom of a long column that is filled with trays or plates.
    • The trays have many bubble caps in them to allow the vapor to pass through.
    • There is a temperature difference across the various trays , they are hot at the bottom and cool at the top
    • The vapor rises in the column.
    • As the vapor rises through the trays in the column, it cools.
    • When a substance in the vapor reaches a height where the temperature of the column is equal to that substance's boiling point, it will condense to form a liquid.
    • The substance with the lowest boiling point will condense at the highest point in the column; substances with higher boiling points will condense lower in the column.
    • The trays collect the various liquid fractions.

     

    Answered by  | 18th Aug, 2010, 05:47: PM

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