Air Chapter Notes | Chemistry for JAMB PDF Download

Introduction

Air is a natural mixture of gases that surrounds the Earth. It is composed of several gaseous constituents, including nitrogen, oxygen, water vapor, carbon dioxide, and trace amounts of noble gases such as argon and neon. The proportions of these gases vary, and their presence in the air is crucial for supporting life on Earth. In this chapter, we will explore the natural gaseous constituents of air, the reasons for its existence as a mixture, the principle involved in the separation of air components, the variation in the composition of air in the environment, and the uses of some of its constituents.

Natural Gaseous Constituents of Air

Nitrogen (N₂)

• Nitrogen is the most abundant gas in the air, comprising approximately 78% of the atmosphere.
• It is a non-reactive gas that plays a crucial role in maintaining atmospheric pressure and diluting oxygen to a breathable level.
• Nitrogen is an essential element for the growth of plants and is often a limiting factor in agriculture.

Oxygen (O₂)

• Oxygen makes up about 21% of the air and is vital for supporting aerobic respiration in living organisms.
• It is required for the combustion of fuels and is crucial for various industrial processes.
• Oxygen is also used in medical settings to assist patients with respiratory difficulties.

Water Vapor (H₂O)

• Water vapor is the gaseous form of water and exists in the air in varying amounts depending on temperature and location.
• It plays a significant role in the Earth's water cycle, contributing to cloud formation and precipitation.
• Water vapor acts as a greenhouse gas, influencing the Earth's climate and temperature regulation.

Carbon Dioxide (CO₂)

• Carbon dioxide is present in trace amounts, making up around 0.04% of the air.
• It plays a crucial role in photosynthesis, enabling plants to convert sunlight into energy and produce oxygen.
• Carbon dioxide levels in the atmosphere have increased significantly due to human activities, contributing to global warming and climate change.

Noble Gases (Argon and Neon)

• Noble gases, such as argon and neon, are present in minute amounts in the air.
• Argon is the most abundant noble gas, constituting about 0.93% of the air.
• These gases are chemically unreactive and are primarily used in various applications, including lighting, lasers, and cryogenics.

Reasons for the Existence of Air as a Mixture

The existence of air as a mixture can be attributed to the following reasons:
Abundance of Different Gases

• The natural distribution and abundance of gases on Earth result in their mixture in the atmosphere.
• Gases are released from various sources such as volcanic activity, respiration, and combustion processes, leading to their continuous presence in the air.

Varying Chemical Properties

• Different gases in the air have distinct chemical properties, such as reactivity and density.
• These variations make it difficult for gases to separate and form distinct layers or compounds, resulting in their mixture.

Principle Involved in the Separation of Air Components

The separation of air components is based on the principle of fractional distillation. This process involves the following steps:
Compression

• Air is compressed using a compressor to increase its pressure.

Cooling

• The compressed air is passed through a series of cooling stages, which decrease its temperature.

Fractional Distillation

• The cooled air is then passed into a fractionating column, where it undergoes fractional distillation.
• The column contains trays or packing material to facilitate separation.
• Different components of air have different boiling points, and as the air is heated, the gases with lower boiling points vaporize first.
• By condensing and collecting the vapor at various stages, the different components of air can be separated.

Variation in the Composition of Air in the Environment

The composition of air can vary due to several factors, including:
Human Activities

• Human activities such as industrial processes, deforestation, and burning of fossil fuels contribute to the release of pollutants and greenhouse gases into the air.
• These activities can alter the composition of air, leading to increased levels of pollutants or greenhouse gases.

Natural Processes

• Natural phenomena like volcanic eruptions, wildfires, and biological processes can release gases into the atmosphere, affecting its composition.

Uses of Air Constituents

Nitrogen

• Nitrogen is widely used in the food industry to preserve freshness, prevent spoilage, and inhibit microbial growth.
• It is also used in the production of ammonia for fertilizers and in various industrial processes such as steelmaking.

Oxygen

• Oxygen is used in medical settings to support patients with respiratory difficulties and in industrial applications such as welding and cutting metals.

Carbon Dioxide

• Carbon dioxide finds applications in the food and beverage industry for carbonation and as a preservative.
• It is also used in fire extinguishers and as a coolant in certain industrial processes.

Noble Gases

• Noble gases, particularly argon and neon, are used in lighting applications such as fluorescent lamps and neon signs.
• They are also employed in lasers, cryogenics, and as shielding gases in welding.

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