Air and atmosphere Flashcards
Carbon monoxide
source: Released due to incomplete combustion of carbon containing fuels, eg. incomplete combustion of carbon-containing fuels
Effects: Binds strongly and forms a stable compound with hemoglobin in red blood cells, Carboxyhemoglobin , which deprives the red blood cells of oxygen. Oxygen cannot be transported to other parts of body, leading to headaches, fatigue and even death
Nitrogen oxides
Source: Formed at high temperatures, such as in a combustion engine or lightning
effects: Causes acid rain when dissolved in rainwater, irritates lungs and eyes
Sulfur dioxide
Source: Naturally produced during volcanic eruptions. Produced during the burning of sulfur containing fossil fuels
Effects: Causes acid rain when it reacts with oxygen in the air and dissolved in rainwater
2SO2 (g) + O2 (g) + 2H2O (l) → 2H2SO4 (aq)
Irritates the eyes and lungs, which causes breathing difficulties
causes inflammation of lungs (bronchitis)
Leads to the erosion of buildings made with metal carbonates
Unburned Hydrocarbons
Sources: Released during incomplete combustion of fuels. eg. in car exhaust and chemical plants
Effects: May cause cancers in long term exposure
Reacts with nitrogen oxides to form ozone at low altitudes, which causes photochemical smog irritating eyes and lungs
Methane
Source: Naturally produced by the decay of organic matter by microorganisms. Produced by poultry due to food digestion and the decay of rubbish in landfills.
Effects: A greenhouse gas that traps the heat from the sun and causes global warming, resulting in drastic weather changes
Ozone (at ground level)
Source: Produced at ground level due to the reaction of nitrogen oxides and unburned hydrocarbons in the presence of sunlight
Effects: Forms photochemical smog that causes eye irritation and respiratory problems
Acid rain
carbon dioxide + water ⇌ Carbonic acid
CO2(g) + H2O(l) ⇌H2CO3(aq)
Sulfur dioxide + water → Sulfurous acid
SO2(g) + H2O(l) → H2SO3(aq)
nitrogen dioxide + water + oxygen → nitric acid
4NO2(g) + 2H2O(l) + O2(g) → 4HNO3(aq)
Acid rain reacts with structures with metal or carbonates (limestone) causing them to corrode and be destroyed. It destroys aquatic habitats by making it too acidic (pH 6.5 to under pH 4). The PH of the soil is also greatly lowered making it unsuitable for plants to survive
Catalytic converters
Catalytic converters are installed in exhaust systems of cars to reduce emissions of Carbon monoxide, Nitrogen oxides and unburned hydrocarbons
These substances undergo redox reactions in the presence of platinum and rhodium crystals catalysts to form less harmful substances
carbon monoxide is oxidised to form carbon dioxide
2CO(g) + O2(g) → 2CO2(g)
Nitrogen oxides is reduced to form Nitrogen gas
2NO(g) + 2CO(g) →N2(g) +2CO2(g)
unburnt hydrocarbons are oxidised to carbon dioxide and steam
2C8H18(g) + 25O2(g) → 16CO2(g) + 18H2O(g)
Flue Gas desulfurisation
Sulfur dioxide is removed from waste gasses emitted from industrial processes through flue gas desulfurisation.
This involves passing waste gasses through calcium carbonate or calcium oxide. Sulfur dioxide is removed from these gases as it reacts w basic substances
Sulfur dioxide + calcium dioxide → calcium sulfite + carbon dioxide
SO2(g) + CaCO3(s) → CaSO3(s) + CO2(g)
Sulfur dioxide + calcium oxide → calcium sulfite
So2(g) + CaO(s) → CaSO3(s)
Calcium sulfite undergoes further oxidation with atmospheric oxygen to form calcium sulfate.
2CaSO3(s) + O2(g) → 2CaSO4(s)
Common atmospheric pollutants
Carbon monoxide, CO
Methane, CH4
Nitrogen oxides, NO & NO2
Ozone, O3
Sulfur dioxide, SO2
Unburnt hydrocarbons, eg. C8H18, C10H20
Importance of the ozone layer
- Ozone in the stratosphere acts as a giant sunscreen,
- filtering out some of the harmful ultraviolet radiation from the sun to protect us from high exposure to UV radiation
- UV radiation can cause skin cancer, genetic mutations and eye damage
Cause of depletion of ozone in the stratosphere (CFCs)
- the depletion of the ozone layer is caused by chloroflurocarbons (CFCs)
- CFCs are widely used as coolants in refrigerators and air conditioners, propellants in aerosols, manufacturing of packing foam
- within the last few decades, large amounts of CFCs have been released into the atmosphere and they remain there for very long as they are very stable
- over the years, they slowly diffuse through air and react with ozone, destroying the ozone layer
Effect of the depletion of the ozone layer
- The depletion of the ozone layer by CFCs alloes more UV radiation to pass through the atmosphere, causing more people to get skin cancer, genetic mutations and eye damage
- Even though now many countries ban the use of CFCs, they are already present in the atmosphere for many years and can still continue to deplete the ozone layer
The carbon cycle
- It is the mechanism that maintains the level of carbon dioxide in the atmosphere
- In order to maintain a constant amount of carbon dioxide in the atmosphere,
- the rate of removal of atmospheric CO2 must be balanced by the rate of return of carbon dioxide gas to the atmosphere
- Rate of removal of CO2 gas from atmosphere = Rate of return of CO2 gas to atmosphere
Processes that return CO2 gas to the atmosphere
- Respiration
Carried out by all living things. Glucose in food is converted to CO2 and water, releasing energy
C6H12O6(aq) + 6O2(g) → 6CO2(g) + 6H2O(l) - Combustion of fuels
Most fuels contain hydrocarbons which produces carbon dioxide when burnt
CH4(g) + 2O2(g) → CO2(g) + 2H2O (l) - Decay and bacterial decomposition
Bacteria breaks down carbon compounds in decaying dead animals and dead plants to produce carbon dioxide
