Suggest the method for the purification of naphthalene.

To separate different fractions of crude oil in the petroleum industry,the method used is:

Explain why an organic liquid vaporises at a temperature below its boiling point during steam distillation.

Given below are two statements: one is labelled as Assertion $(A)$ and the other is labelled as Reason $(R)$:
Assertion $(A):$ $A$ simple distillation can be used to separate a mixture of propanol and propanone.
Reason $(R):$ Two liquids with a difference of more than $20^{\circ}C$ in their boiling points can be separated by simple distillation.
In the light of the above statements,choose the most appropriate answer from the options given below:

Give the answer of the following questions in short:
$(i)$ When is simple distillation used?
$(ii)$ When is fractional distillation used?
$(iii)$ Which liquid is obtained first in fractional distillation?
$(iv)$ Which liquid is cooled first in fractional distillation?
$(v)$ What happens in the fractional column?

What is the characteristic of $R_f$ value?