Air quality Flashcards
What is the composition of air
- 78% N2
- 21% O2
- 1% noble gases
- 0.03% CO2
What are some common atmospheric pollutants
- CO
- NO
- NO2
- O3
- CH4
- SO2
- Unburned hydrocarbons
In fractional distillation, which substance is removed from the top
Lowest boiling point
What are the sources of CO
Incomplete combustion of carbon-containing fuels
What are the harmful effects of SO2
- Causes eye irritation and breathing difficulties
- Causes acid rain which destroys aquatic life, damages vegetation, and corrodes metal, limestone and marble structures
What are the sources of SO2
- Combustion of fossil fuels that contain sulfur as impurities
- Volcanic eruptions
What are the harmful effects of CO
- Binds permanently with haemoglobin to form carboxyhaemoglobin, reducing ability of red blood cells to transport oxygen
How to prevent or treat CO pollution
- Fit motor vehicles with catalytic converters
- Catalytic converters oxidise CO to CO2
How to prevent SO2 pollution
- Remove sulfur impurities from fossil fuels
- Flue gas desulfurisation
What is flue gas desulfurisation
- Waste gases including SO2 known as flue gases
- Waste gases treated with wet mixture of CaCO3
- SO2 reacts with wet CaCO3 to form CO2 and calcium sulfite
- CaSO3 is further oxidised with O2 to form CaSO4
What are the harmful effects of NO and NO2
- Causes eye irritations and breathing difficulties
- Produces acid rain
What are the sources of NO and NO2
- Internal combustion of motor vehicles when N2 and O2 from air react at high temperature
- Occurs naturally from lightning activity as heat released by lightning allows oxygen and nitrogen in air to react
How to prevent and treat NO and NO2 pollution
- Fit motor vehicles with catalytic converters
- Catalytic converters reduce NO and NO2 to N2
How is acid rain formed
- SO2 reacts with oxygen and water vapour in air to form H2SO4
- NO2 reacts with oxygen and water vapour in air to form HNO3
- Typical acid rain is at pH 4
What are hydrocarbons
Compounds that contain hydrogen and carbon only
How do motor vehicles cause pollution
- Hydrocarbons undergo complete combustion in excess oxygen to form CO2 and water vapour
- Hydrocarbons undergo incomplete combustion in limited oxygen to form CO and water vapour
- N2 and O2 react at high temperature to form NO and NO2
What are catalytic converters
- Contain ceramic elements coated with platinum and rhodium catalysts
- Enclosed by stainless steel casing
How do catalytic converters reduce pollution
- CO oxidised to CO2
- NO and NO2 reduced to form N2
- Unburned hydrocarbons oxidised to form CO2 and H2O
Oxidation with oxygen, reduction with carbon
What are other ways to reduce air pollution by motor vehicles
- Use cleaner fuels like hydrogen
- Use electric vehicles
What processes is the carbon cycle made up of
- Respiration
- Combustion
- Decomposition
- Photosynthesis
- Ocean uptake
What are the main greenhouse gases
- CO2
- CH4
How is carbon dioxide produced
- Respiration forms CO2 and water vapour
- Combustion of fossil fuels produces CO2
- Decomposition of plants and animals produces CO2
How is carbon dioxide removed
- Photosynthesis requires CO2 and H2O
- Oceans act as huge sinks for CO2
What are CFCs
chlorofluorocarbon molecules
- Compounds that contain only chlorine, fluorine and carbon
- Gases at r.t.p.
- Not broken down in ground-level atmosphere
What are the sources of CFCs
- Aerosol propellants
- Coolants fluids for refrigerators and air-conditioners
Why can 1 chlorine atom destroy 10000 ozone molecules
1) CFCl3 –> CFCl2 + Cl
2) Cl + O3 –> ClO +O2
3) ClO + O –> Cl + O2
- Chlorine atom reacts with ozone molecules to form ClO and O2
- UV breaks down O2, so ClO can react with O to form Cl again
- Process repeats itself
Describe the depletion of the ozone layer
- Earth surrounded by layer of ozone gas 40km above ground level, protecting planet from UV rays
- Ozone layer destroyed by chlorine atoms produced from CFCs
- CFCs are decomposed by UV light from sun, forming reaction chlorine atoms
- Chlorine atoms react with ozone molecules to form O2 and chlorine monoxide
- Excessive UV light allowed to reach Earth
