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

The answer is (b) oxygen has a higher boiling point than nitrogen.

Step 1: Identifying the Correct Property

To understand why fractional distillation can separate oxygen from air, we need to consider properties related to boiling points, densities, reactivity, and periodic table groups.

Step 2: Analyzing Boiling Points

Fractional distillation is based on differences in boiling points of substances. Oxygen has a boiling point of -183°C, while nitrogen has a boiling point of -196°C. This indicates that oxygen has a higher boiling point than nitrogen.

Step 3: Considering Other Properties

While oxygen and nitrogen have different densities, reactivity levels, and belong to different groups of the periodic table, these properties do not influence fractional distillation which relies on boiling points.

Step 4: Selecting the Correct Statement

Since fractional distillation separates substances based on boiling points, the correct statement is (b) oxygen has a higher boiling point than nitrogen.

Key Concepts

Boiling Points

Understanding boiling points is crucial when learning about fractional distillation. Boiling points are the temperatures at which a liquid becomes a gas. Every substance has its own unique boiling point, which is determined by its chemical nature. For instance, when we look at oxygen and nitrogen in the air, we find that their different boiling points enable their separation. Oxygen turns into gas at \(-183^{\circ}C\), whereas nitrogen boils at \(-196^{\circ}C\).
This difference is sizable and forms the basis for their separation through fractional distillation.

• Lower boiling point of nitrogen allows it to become gas first.
• Higher boiling point of oxygen means it remains liquid longer when cooling air.

Knowing boiling points helps understand why fractional distillation is an efficient method for separating gases like oxygen and nitrogen.

Separation Techniques

Fractional distillation is a fascinating separation technique used to separate mixtures of liquids with different boiling points. Here, the mixture is first turned into vapor, which is then cooled back into liquids.

As various components have different boiling points, they evaporate and condense at different times, which makes them easier to separate.

• Initial heating vaporizes gases from the air.
• Coolers turn them back into liquid at varying temperatures.
• Collection chambers separate gases based on boiling points.

This technique is not only effective for separating air but is also commonly used in the petrochemical industry to refine crude oil.

Air Composition

Our air is a complex mixture of different gases. Understanding its composition provides insights into how separation techniques work. The major components of air include:

• Nitrogen (78%)
• Oxygen (21%)
• Argon (0.93%)
• Carbon Dioxide (0.04%)

These gases are present in varying amounts but contribute differently to the chemical processes occurring in the atmosphere. Each gas has unique boiling points, which allows their separation through techniques like fractional distillation. Understanding this composition is key to industries that require pure oxygen or nitrogen for various applications.

Properties of Oxygen and Nitrogen

Oxygen and nitrogen, two of the most abundant gases in the atmosphere, have unique properties that enable their separation through fractional distillation.

**Oxygen**

• Boiling point: \(-183^{\circ}C\)
• Supports combustion processes
• Vital for respiration in living organisms

**Nitrogen**

• Boiling point: \(-196^{\circ}C\)
• Inert nature; does not easily react with other substances
• Used in creating inert atmospheres in various industrial processes

The differences in their chemical properties, particularly their boiling points and reactivity, make fractional distillation a perfect technique for separating them from the air.