Question

Steam distillation is used to purify a compound which is steam principle volatile and insoluble in water. The impurities should not be steam volatile. It is based on the principle that liquid will boil when partial vapour presure of liquid and partial vapour pressure of steam both become equal to atmospheric presure `P=p_(1)+p_(2)`.
It reduces the boiling point of liquid.
`("Wt. of water distilled")/("Wt. of substance distilled")=`
`("M. Wt. of water" xx V.P. " of steam")/(M. Wt. "of substance" xx "V.P. substance")`
Which of the following cannot be separated by steam distillation?
A. Nitrobenzene
B. Essential oil
C. Aniline
D. Glycerol

Answer 1

Correct Answer - D
a,b and c are steam volatile, therefore, can be separated by steam distillation and they are insoluble in water. Glycerol decomposes at its boiling point as well as it is soluble in water. It cannot be separated by steam distillation, rather it is purified by distillation under reduced pressure.