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Air and Atmosphere - Atmospheric Pollution

Grade 7ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

Air Pollution is the contamination of air by harmful substances such as chemicals, particulate matter, or biological materials that cause harm to humans and the environment.

Major pollutants include Carbon monoxide (COCO), Nitrogen oxides (NOxNO_x), Sulfur dioxide (SO2SO_2), and Chlorofluorocarbons (CFCsCFCs).

The Greenhouse Effect is the process where gases like CO2CO_2 and CH4CH_4 trap the sun's heat in the atmosphere. An increase in CO2CO_2 concentration leads to Global Warming.

Acid Rain is formed when pollutants like SO2SO_2 and NO2NO_2 react with water vapor (H2OH_2O) in the atmosphere to form Sulfuric acid (H2SO4H_2SO_4) and Nitric acid (HNO3HNO_3).

The Ozone layer (O3O_3) in the stratosphere protects Earth from harmful Ultraviolet (UV) radiation. It is depleted by CFCsCFCs used in refrigeration and aerosols.

Incomplete combustion of fossil fuels produces Carbon monoxide (COCO), a highly poisonous gas that reacts with hemoglobin to form carboxyhemoglobin, reducing the oxygen-carrying capacity of blood.

📐Formulae

S+O2SO2S + O_2 \rightarrow SO_2

2SO2+O2+2H2O2H2SO4 (Formation of Sulfuric Acid)2SO_2 + O_2 + 2H_2O \rightarrow 2H_2SO_4 \text{ (Formation of Sulfuric Acid)}

4NO2+2H2O+O24HNO3 (Formation of Nitric Acid)4NO_2 + 2H_2O + O_2 \rightarrow 4HNO_3 \text{ (Formation of Nitric Acid)}

CO2+H2OH2CO3 (Formation of Carbonic Acid)CO_2 + H_2O \rightarrow H_2CO_3 \text{ (Formation of Carbonic Acid)}

2C+O2 (insufficient)2CO (Incomplete Combustion)2C + O_2 \text{ (insufficient)} \rightarrow 2CO \text{ (Incomplete Combustion)}

💡Examples

Problem 1:

Explain how sulfur dioxide emitted from factories contributes to the damage of historical monuments like the Taj Mahal.

Solution:

SO2+H2OH2SO3SO_2 + H_2O \rightarrow H_2SO_3 (Sulfurous acid) and subsequent oxidation to H2SO4H_2SO_4.

Explanation:

Sulfur dioxide (SO2SO_2) reacts with water vapor and oxygen in the air to form Sulfuric acid (H2SO4H_2SO_4). When it rains, this acid falls as 'Acid Rain'. It reacts with the calcium carbonate (CaCO3CaCO_3) of the marble, causing it to corrode and yellow, a phenomenon known as 'Stone Cancer'.

Problem 2:

Why is it dangerous to sleep in a closed room with a coal fire burning?

Solution:

2C+O22CO2C + O_2 \rightarrow 2CO

Explanation:

In a closed room, oxygen (O2O_2) supply is limited, leading to the incomplete combustion of coal which produces Carbon monoxide (COCO). COCO is a colorless, odorless gas that binds with hemoglobin in the blood more strongly than oxygen, leading to suffocation and potentially death.

Atmospheric Pollution - Revision Notes & Key Formulas | ICSE Class 7 Science