Why oxygen can be obtained from air by fractional distillation?

Introduction:
Fractional distillation is a process used to separate a mixture of liquids with different boiling points. It is based on the principle that each component in the mixture has a unique boiling point, and by heating the mixture, the component with the lowest boiling point vaporizes first. In the case of air, it is composed of various gases, including oxygen and nitrogen. By subjecting air to fractional distillation, it is possible to obtain oxygen as a separate component.

Explanation:
The correct answer to why oxygen can be obtained from air by fractional distillation is option C, which states that "oxygen has a higher boiling point (b.p.) than nitrogen." Let's explore this further:

Oxygen and nitrogen:
- Oxygen (O2) and nitrogen (N2) are two of the major components of air, constituting approximately 21% and 78% respectively.
- Both oxygen and nitrogen are diatomic molecules, meaning they exist as pairs of atoms.
- Oxygen has a boiling point of -183 °C (-297.2 °F), while nitrogen has a boiling point of -196 °C (-320.4 °F).

Fractional distillation:
- In the process of fractional distillation, air is first cooled to a very low temperature, typically around -200 °C (-328 °F), to liquefy the gases.
- The liquefied air is then gradually heated, causing the different components to vaporize at their respective boiling points.
- The vaporized gases are collected and condensed into separate containers.

Boiling points:
- The reason why oxygen can be obtained from air by fractional distillation is due to its higher boiling point compared to nitrogen.
- When air is heated during fractional distillation, the nitrogen vaporizes first, as its boiling point (-196 °C) is lower than that of oxygen (-183 °C).
- As nitrogen vaporizes and is collected, the remaining liquid becomes enriched in oxygen.
- By continuing to heat the mixture, the oxygen eventually vaporizes, allowing it to be collected separately.

Conclusion:
In summary, oxygen can be obtained from air by fractional distillation because it has a higher boiling point than nitrogen. By subjecting air to low temperatures and gradually heating it, the different components can be vaporized and collected separately based on their boiling points.