Ozone Layer and Depletion

Study Notes

Ozone (O3O_3O3) is a pale blue gas with a pungent odor.
Ozone is located in the upper layer of the atmosphere, which surrounds the Earth.
The ozone layer acts as a barrier against harmful ultraviolet (UV) radiation from the sun.
Chlorofluorocarbons (CFCs), containing chlorine, fluorine, and carbon, are used in aerosol propellants and refrigerants.
CFCs contribute to ozone layer depletion.
CFCs rise to the stratosphere and break down into chlorine atoms due to sunlight.
Chlorine atoms react with ozone, forming chlorine oxide and oxygen, reducing ozone concentration.

Ozone layer depletion allows more UV radiation to reach Earth's surface.
Excessive UV radiation increases the risk of skin cancer, premature aging of the skin, and eye damage (cataracts).

Catalytic converters in vehicle exhaust systems reduce pollutants like carbon monoxide, nitrogen oxides, and unburnt hydrocarbons.
Flue gas desulfurization removes sulfur dioxide from the waste gases produced by power plants burning sulfur-containing fossil fuels.
Using low-sulfur fuels minimizes sulfur dioxide emissions from vehicle engines.

Catalytic converters use transition metals like platinum and rhodium as catalysts.
Redox reactions in the converter convert harmful exhaust gases into harmless ones.
Nitrogen monoxide reacts with carbon monoxide to form nitrogen and carbon dioxide.
Carbon monoxide oxidizes to carbon dioxide.
Nitrogen oxides reduce to nitrogen.
Unburnt hydrocarbons like octane oxidize to carbon dioxide and water vapor.

Flue gas desulfurization removes sulfur dioxide from flue gas, reducing atmospheric sulfur dioxide levels.

Common air pollutants include unburnt hydrocarbons (CxC_xCx HyH_yHy), ozone (O3O_3O3), sulfur dioxide (SO2SO_2SO2), and nitrogen oxides (NOxNO_xNOx).
Sources of air pollutants include vehicle engines, chemical plants, and fossil fuel combustion.
Effects of air pollutants on health and the environment include respiratory problems, eye irritation, photochemical smog, and acid rain.
Unburnt hydrocarbons cause eye and lung irritation, breathing difficulties, and contribute to photochemical smog.
Ozone causes eye and lung irritation, breathing difficulties, headaches, chest pain, and affects plant photosynthesis.

Acid rain is rainwater with high levels of sulfuric acid and nitric acid.
Sulfur dioxide (SO2SO_2SO2) and nitrogen dioxide (NO2NO_2NO2) are acidic oxides that react with oxygen and water to form sulfuric acid and nitric acid, respectively:
- 2SO2(g)+O2(g)+2H2O(l)−>2H2SO4(aq)2SO_2(g) + O_2(g) + 2H_2O(l) -> 2H_2SO_4(aq)2SO2(g)+O2(g)+2H2O(l)−>2H2SO4(aq)
- 4NO2(g)+O2(g)+2H2O(l)−>4HNO3(aq)4NO_2(g) + O_2(g) + 2H_2O(l) -> 4HNO_3(aq)4NO2(g)+O2(g)+2H2O(l)−>4HNO3(aq)
Acid rain damages metal structures, buildings, aquatic life, and soil nutrients.