Air Pollution

🌬️ Air and Its Composition

🔹 Definition of Air:

Air is a mixture of gases that forms the Earth’s atmosphere. It is not a compound, as it contains different gases physically mixed together and not chemically combined.

🔹 Volume Composition of Dry Air:

Water vapour and dust particles are also present in varying amounts depending on humidity and environmental conditions.

🌱 Photosynthesis and Respiration

🔹 Photosynthesis:

Plants take in carbon dioxide and water, using sunlight and chlorophyll to produce glucose and oxygen:

6CO₂+6H₂O → C₆H₁₂O₆+ 6O₂ ​

• Helps reduce CO₂ and release O₂ into the air.
• Maintains atmospheric balance.

🔹 Respiration:

Living organisms (plants, animals) use oxygen to break down food and release carbon dioxide and energy:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy

• Increases CO₂ in the air.

🧪 Experiment to Find Oxygen Percentage in Air

Apparatus: Wet iron wool in a measuring cylinder inverted over water.

Procedure:

1. Place moist iron wool inside a test tube or measuring cylinder.
2. Invert it in a water trough.
3. Leave for a few days.
4. Iron reacts with oxygen to form iron oxide (rust), decreasing the gas volume.

Observation: About 21% decrease in gas level = oxygen content in air.

🏭 Major Air Pollutants

🌍 Greenhouse Gases & Global Warming

🔹 Major Greenhouse Gases:

• Carbon dioxide (CO₂)
• Methane (CH₄)
• Nitrous oxide (N₂O)
• Water vapour (H₂O)
• Ozone (O₃)

🔹 Sources:

• CO₂: Combustion of fossil fuels, deforestation
• CH₄: Agriculture (rice fields, cattle), landfills
• N₂O: Fertilizers, industrial processes

🔹 Effects of Global Warming:

• Rising global temperatures
• Melting polar ice caps
• Rising sea levels
• Extreme weather conditions
• Habitat loss and biodiversity decline

🌧️ Acid Rain

🔹 Formation:

• Sulfur dioxide (SO₂) + water → sulfurous acid (H₂SO₃)
• Nitrogen oxides + water → nitric acid (HNO₃) & nitrous acid (HNO₂)

SO2+H2O→H2SO32NO2+H2O→HNO2+HNO3SO_2 + H_2O → H_2SO_3 \\ 2NO_2 + H_2O → HNO_2 + HNO_3SO2​+H2​O→H2​SO3​2NO2​+H2​O→HNO2​+HNO3​

🔹 Effects:

• Kills aquatic life in lakes and rivers
• Damages crops and forests
• Corrodes buildings (especially limestone and marble)
• Harms human lungs and skin

♻️ Reducing Air Pollution

🔹 Industrial Solutions:

• Use scrubbers in chimneys to remove harmful gases
• Switch to cleaner fuels (natural gas, hydrogen)
• Use catalytic converters in vehicles to reduce CO, NOx, and hydrocarbons

🔹 Personal & Governmental Actions:

• Promote renewable energy
• Encourage public transport, carpooling, and electric vehicles
• Ban open burning and enforce environmental regulations
• Plant more trees to absorb CO₂

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