A Level Chemistry OCR Practice Exam

What is the primary purpose of fractional distillation?

1. To separate solid components of a mixture

2. To separate components in a mixture based on boiling point differences

3. To purify water from impurities

4. To synthesize chemical compounds

The correct answer is: To separate components in a mixture based on boiling point differences

Fractional distillation is primarily used to separate components in a mixture based on their differences in boiling points. This technique relies on the principle that when a liquid mixture is heated, its components will vaporize at different temperatures. As the mixture is heated, the component with the lowest boiling point evaporates first, and as the vapors rise through the distillation column, they can be cooled and condensed back into liquid form. The fractional distillation process allows for the separation of these different components in a more efficient manner than simple distillation, especially when the boiling points of the components are relatively close together. This method is particularly useful in separating complex mixtures, such as crude oil into its various fractions like gasoline, diesel, kerosene, and other hydrocarbons, which is essential in the petroleum industry. The effectiveness of fractional distillation in separating mixtures based on boiling point differences makes it a fundamental process in chemical engineering and laboratories.