Question

The acetone-cyclohexane system also exhibits positive deviations from Raoult’s Law. Sketch the expected temperature-composition phase diagram for this system given the following: bp (pure acetone) = 56.5oC, bp (pure cyclohexane) = 81.4oC, azeotrope occurs at ca. 0.25 mole fraction cyclohexane and boils at 53 oC. All bp’s are cited for P = 1 atmosphere.

State the two possible eventual outcomes if mixtures of acetone and cyclohexane were repeatedly distilled in an effort to separate the two components completely (give what would be expected as a distillate and what would be expected to be left in the distillation flask for starting solution compositions having a mole fraction of cyclohexane less than or greater than the azeotrope composition).

Answer 1

As the difference in B.P. of acetone and cyclohexane is less than 50 deg C, so they can not be separated by simple distillation. So fractional distillation is carried out.Inthis, the vapors formed from the boiling mixture rise into the fractionating column where they condense on the column's packing. The condensate is more concentrated in the lower boiling compound than the mixture in the distillation flask. As vapors continue to rise through the column, the liquid that has condensed will revaporize. Each time this occurs the resulting vapors are more and more concentrated in the more volatile substances.