Chemistry Keypoints: Air; Air is a natural mixture of gases that surrounds the Earth. It consists of a variety of gaseous constituents, including nitrogen, oxygen, water vapour, carbon dioxide, and noble gases like argon and neon.
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The natural gaseous constituents and their proportion in the air:
Nitrogen: This is the most abundant gas in the air and makes up about 78% of the air. Nitrogen is essential for the growth of plants and is used to manufacture ammonia, which is an important fertilizer.
Oxygen: Oxygen makes up about 21% of the air. It is essential for respiration and combustion reactions. All animals need oxygen to breathe, and plants use it in the process of photosynthesis.
Water vapour: Water vapour is a small but significant component of air. Its amount in air varies depending on temperature and humidity levels.
Carbon dioxide: Carbon dioxide makes up a small percentage of the air, about 0.04%. It is essential for photosynthesis in plants, but high levels of carbon dioxide can contribute to global warming.
Noble gases: Argon and neon are noble gases that make up a very small percentage of the air. These gases are relatively inert and have limited commercial uses, but argon is used in welding and neon is used in neon lights.
Air as a mixture and some uses of the noble gas:
Air is a mixture of gases and is not a compound. This means that the different components of air can be separated using various separation techniques. For example, liquid air can be separated into its components through a process called fractional distillation.
The noble gases in the air have limited commercial uses due to their inertness. However, argon is used in welding to provide an inert atmosphere that prevents the oxidation of the metal being welded. Neon is used in neon lights to produce a characteristic bright, colourful glow.
Conclusion
In conclusion, the air is a mixture of gases with varying proportions. Its components have a variety of uses, from providing essential nutrients for plant growth to enabling combustion and respiration in animals. The separation of air components is important for a range of industrial and scientific applications, and the noble gases in the air have niche commercial uses.
(i) Reasons for the existence of air as a mixture:
Air exists as a mixture of gases because it is easier for gases to mix with each other than to form compounds. The molecules of gases are in constant random motion, which enables them to mix with each other. Additionally, the gravitational pull of the Earth is not strong enough to hold lighter gases like nitrogen and oxygen in a concentrated layer, which would make it difficult for animals to breathe.
(ii) Principle involved in the separation of air components:
The separation of air components is done through a process called fractional distillation. The principle behind this process is that the boiling points of the different components of air are different. By cooling and compressing air, it is possible to liquefy the components, and then separate them by boiling off the components with lower boiling points first.
(iii) Reasons for the variation in the composition of air in the environment:
The composition of air can vary depending on the location, altitude, and weather conditions. For example, air at higher altitudes has a lower concentration of oxygen than air at sea level. The air in cities and industrial areas can have higher concentrations of pollutants, including carbon monoxide, sulfur dioxide, and nitrogen oxides.
(iv) Uses of some of the constituents of air:
- Nitrogen: It is used in the production of ammonia for fertilizers, and in the food and beverage industry for packaging and preservation.
- Oxygen: It is essential for respiration and combustion reactions, and is used in the production of steel, chemicals, and medical oxygen for patients with respiratory problems.
- Carbon dioxide: It is used in the food and beverage industry for carbonation and preservation, and in fire extinguishers.
- Noble gases: Argon is used in welding and neon is used in neon lights for signage and artistic displays. Helium is used in balloons and for cooling in nuclear reactors.