Question

During fractional distillation, the crude petroleum is heated to a temperature of about
A. ${600}^{o}C$
B. $400-{500}^{o}C$
C. ${200}^{o}C$
D. ${100}^{o}C$

Answer 1

Hint: The process of separating a substance into its fractions or parts by taking advantage of different vapour pressure of those substances is known as Fractional distillation. It is frequently used as a synonym with distillation as it refers to the separation of components in a mixture having difference in their boiling point.

Complete answer:
In fractional distillation, a long fractionating column is fitted above the mixture in which several condensers are placed at different heights. The bottom part of this fractionating column is taken hot while it is cool at the top. Components with high boiling point tend to condense at the bottom while the substances with lower boiling points condense at the top of the fractionating column.
We know that crude petroleum or oil is a mixture of several molecules of hydrocarbons which is evaporated and its vapours condense at different temperatures in the fractionating column. Each fraction consists of molecules of hydrocarbon with the same number of carbon atoms and with a similar range of boiling points. Condensation of different hydrocarbons at certain range of temperature is shown as follows:

Hence, during fractional distillation crude oil or petroleum is heated to a temperature of about $400-{500}^{o}C$ which allows most of the oil to evaporate and enter the column.
Thus, option (B) is the correct answer.

Note:
It is important to note that the temperature at the bottom is always considered higher so that the hydrocarbons with longer carbon chains can fall out at the bottom and the shorter carbon chains will go upwards in the column until they hit a temperature at which they can be condensed.