The fractions of crude oil are best separated by

Analysis

The question asks for the most effective method used to separate the various components (fractions) found in crude oil.

Concept Explanation

Crude oil is a complex mixture of hydrocarbons with different molecular sizes and chain lengths. Because these hydrocarbons have different molecular masses, they possess different boiling points.

To separate these components, we use a process that relies on these varying boiling points. When crude oil is heated in a fractionating column, the components vaporize and rise. As the vapors rise, they cool and condense at different levels of the column based on their specific boiling points. This process is known as fractional distillation.

Step-by-Step Solution

1. Understand the mixture: Crude oil is a liquid mixture of many different substances (petrol, kerosene, diesel, bitumen, etc.).
2. Evaluate the options: • Steam distillation: Used for substances that decompose at their boiling points or are immiscible with water (e.g., essential oils). • Fractional crystallization: Used to separate solids based on differences in solubility at different temperatures. • Precipitation: Used to form a solid from a solution, usually through a chemical reaction. • Fractional distillation: Specifically designed to separate liquids that are miscible and have boiling points that are relatively close to each other.
3. Conclusion: Since crude oil is a mixture of liquids with different boiling points, fractional distillation is the industrial standard for separating it into useful fractions.

Exam Tip

Whenever you see a question about separating crude oil, always look for the word "fractional" and "distillation". Remember that the column used in the refinery is called a "fractionating column."