Problem 45 - A Complete Resource Book in Chemistry for JEE Main

Question

It is possible to obtain oxygen from air by fractional distillation because (a) oxygen has a lower density than nitrogen (b) oxygen has high boiling point than nitrogen (c) oxygen is more reactive than nitrogen (d) oxygen is in a different group of the periodic table from nitrogen.

Step-by-Step Solution

Answer

(b) oxygen has high boiling point than nitrogen.

Step 1: Understanding Fractional Distillation

Fractional distillation is a separation process used to separate components in a mixture based on their boiling points. Substances with lower boiling points vaporize first, and substances with higher boiling points remain in liquid form longer.

Step 2: Comparing Boiling Points

Oxygen and nitrogen are both components of air. In the context of fractional distillation, the primary characteristic of interest is the boiling point of each component. Oxygen has a boiling point of approximately -183°C, whereas nitrogen has a boiling point of around -196°C.

Step 3: Analyzing Given Options

Evaluate each option to determine which aspect of oxygen and nitrogen supports its separation via fractional distillation. Option (a) focuses on density, (b) on boiling points, (c) on reactivity, and (d) on the periodic table grouping. Effective separation by fractional distillation relies on differences in boiling points.

Step 4: Identifying the Correct Answer

Given that fractional distillation separates substances based on boiling points, the correct choice is related to this property. Since oxygen has a higher boiling point than nitrogen, oxygen can be separated from nitrogen by fractional distillation after nitrogen boils off.

Key Concepts

Boiling Points

Boiling points play a crucial role in understanding how substances transition between liquid and vapor forms. Each substance has a specific boiling point, the temperature at which it transitions from a liquid to a gas. For instance, water boils at 100°C, turning into steam upon reaching this point. Boiling points are dependent on the pressure of the environment and the intermolecular forces present in the substance. In separation processes such as fractional distillation, these boiling points are not just useful, they're essential for efficiently separating components of a mixture. Different substances have different boiling points because of varying molecular structures, bond strengths, and attractions between particles. In the fractional distillation of air, nitrogen with its lower boiling point of approximately -196°C vaporizes before oxygen, which boils at around -183°C. This temperature difference enables the effective separation of these gases in a controlled environment.

Separation Processes

Separation processes allow us to isolate specific components from mixtures, which can be very beneficial in various fields like chemical engineering, food technology, and the production of industrial gases. One common and effective separation process is fractional distillation. This technique is particularly valuable when dealing with liquid mixtures that are miscible, meaning they blend together into a uniform mixture. Fractional distillation hinges on the premise that each component in a mixture has a distinct boiling point.

• The substance with the lowest boiling point will vaporize first and can be collected separately as it condenses back to liquid.
• Following this, components with progressively higher boiling points are similarly boiled off and captured.

By tapping into these differences, we can separate complex mixtures into their individual elements. This is exactly how oxygen and nitrogen can be separated from the air, with nitrogen boiling off first due to its lower boiling point.

Oxygen and Nitrogen

Oxygen and nitrogen are two of the primary gases in Earth's atmosphere, making up approximately 21% and 78% of the air, respectively. Despite their abundance and close proximity to each other, they have quite different physical properties, which are advantageous in separation processes such as fractional distillation. Firstly, nitrogen has a lower boiling point (-196°C) compared to oxygen (-183°C). This means that during fractional distillation, nitrogen turns into a gas at a lower temperature than oxygen, allowing these two gases to be separated by carefully controlling the temperature. Additionally, these gases have different roles in industrial and natural processes. Oxygen is essential for combustion and respiration, allowing living organisms to turn food into energy. Nitrogen, on the other hand, is significant for providing an inert atmosphere for sensitive processes and for creating ammonia for fertilizers. Thus, separating these gases efficiently has numerous practical applications in industries, supplying pure gases for specific needs.