Question

Gasoline is obtained from crude petroleum oil by its
A. Fractional distillation
B. Vacuum distillation
C. Steam distillation
D. Pyrolysis

Answer 1

Hint: A complex mixture of different hydrocarbons which is refined from crude petroleum oil is termed as gasoline. It is used as fuel in engines. It includes several hydrocarbon molecules like methane, ethane, propane, butane etc.

Complete step by step answer:
The unrefined or unprocessed oil is known as crude oil. When the liquid petroleum is recovered directly from oil, then it is termed as crude oil.
There are different hydrocarbons in crude oil, which have different boiling points. They are arranged depending on their number of carbon atoms. We can separate the different hydrocarbons by using this difference in boiling point. Such a method is known as fractional distillation. Generally, the fractionating column is cool at top. Thus when they rise, the vapors get cooled. When the vapors reach to the column, it gets condensed to a tray. These vapors have less temperature than its boiling point. When all the gases reach the tray, the hydrocarbons which have less molecular weight in the condensed liquid get boiled and move up to the column. Thus different fractions of hydrocarbons are formed.
Fractional distillation is used since the difference in the boiling points is very less. Vacuum distillation is used for separating mixtures having high boiling point difference.

So, the correct answer is Option A.

Note: After cracking method, the products formed are moved to another fractionating column for separating these products.
Temperature range is needed for the mixture to separate using fractional distillation. Cracking and unification methods are required to change one fraction into another. Larger chains are converted to smaller chains by cracking method. Unification is simply the reverse of the cracking method.