IB Chemistry Option E: environmental chemistry

Phosphate ions
Weakly acidic soil
Nitrogen ions
High ph
Calcium and magnesium
Unavailable at high ph
Copper and zinc
Intermediate ph
Aluminium and iron
Low ph
Carbon monoxide
Anthro: incomplete combustion of fossil fuels
Natural: anaerobic decomposition of organic matter
Catalytic converter – how does it work? 3 equations
Hot gases and air are passed over a platinum based catalyst. Gases are adsorbed onto surface of metal. Carbon monoxide, vocs, no
2CO O2 – 2CO2
CH – CO2 H2O
NO 2CO – 2CO2 N2
Nitrogen: source and control
Anthro: combination of nitrogen and oxygen in internal combustion engine at high temperatures.
Natural: lighting storms
Control: catalytic convertors with high fuel to low air ratio.
Volatile organic compounds
Organic compounds…duh
Anthro: unburned petroleum. Hydrocarbons from petrol. Solvents.
Natural: decomposition of organic matter in soil.
Control: catalytic convertors
Sulfur oxides
Anthro: combustion of coal containing Sulfur in factories
Natural: volcanic activity and oxidation of h2s in decay of organic matter
Control: remove Sulfur from fossil fuels.
Alkaline scrubbing
Fluidized bed composition
Alkaline scrubbing
Alkaline mixture (calcium
Oxide or calcium carbonate) sprayed into exhaust gases.
Forms calcium Sulfate – deposited in landfill or used to make plasterboard.
Fluidized combustion method
Coal mixed with powdered limestone on metal plate.
Air flow carries limestone and particles over plate.
Heat from combustion of coal causes calcium carbonate to break into cao and co2.
Calcium oxide reacts with Sulfur to produce calcium Sulfate l
Electrostatic precipitation
Gas is ionised
Electrons collect on particulates
Particulates are Attracted to positive collector plates.
Collector plates are shaken
Particulates
Anthro: spot( incomplete combustion of hydrocarbons)
Natural: dust from beak up of matter. Sulfur from
Volcanic eruptions.
Control: electrostatic precipitation.
Acid deposition
Process by which acidic particles, gases and precipitation leave the atmosphere.
Origins of acid deposition
S O2 – SO2
SO2 H20 – H2SO3
2SO2 O2 – 2SO3
SO3 H20 – H2SO4
N2 O2 – 2NO
2NO2 H2O – H2NO3 HNO2
Environmental effects of acid deposition. Methods to counteract.
Erodes statues and buildings of calcium carbonate,
Increases rate of rusting.
Washes nutrients from soil. Releases al3 .
Stunted growth and leaf loss
Fish cannot survive in acidic conditions – al3 ions dissolve and reduced ability to take oxygen.
HNO2 and HNO3 = eutrophication
Greenhouse effect
Warming of the earth caused by infrared radiation, emitted by the earth’s surface- absorbed by various gases in earth’s atmosphere responsible are water vapour, CH4, CO2, nitrous oxide
List main greenhouse gases and discuss their relative effects.
CO2 – combustion of fossil fuels
H2O – evap of water and lakes
CH4 – anaerobic decomposition.
Primary pollutants of photochemical smog and sources
Nitrogen monoxide – NO= internal combustion engine – at HIGH temperatures.
VOC’s – car exhausts
Name secondary pollutants in photochemical smog
Nitrogen dioxide – NO2
Ozone
Aldehydes
Nitric acid
PANs
Conditions necessary for smog to occur.
Bowl shaped cities cause thermal inversions. Thermal inversion traps pollutants – which collect over city.
Vocs and NOx in atmosphere
How are secondary pollutants formed in smog?
2NO O2 – 2NO2
SUNLIGHT is essential to sub reactions!
NO2 – NO O•
O2 O• – O3
Peroxy radicals:
CH3C(O)OO• NO2 ~ CH3C(O)OONO2
Description of formation and depletion of ozone.
F:O2 UV = 2O•
O• O2 = O3
D: O3 UV = O2 O•
O3 O• = 2O2
List ozone depleting substances and their sources
NO• and NO2 – internal combustion engine – jet aircraft.
Chlorofluorocarbons CFCs aerosols, refrigerants, solvents, foaming agents, plastics
Discuss alternatives to CFCs inc. toxicity, flammability, relative weakness of C-Cl bond and ability to absorb infrared radiation.
Hydrocarbons: flammables and highly toxic, C-H stronger than C-Cl bond.
Fluorocarbons: not flammable, no know toxic effects, C-F bond very strong compares to C-Cl.
Hydrofluorocarbons: not flammable, low toxicity, C-F stronger
Define biological oxygen demand
Quantity of oxygen needed to oxidise organic matter in a sample of water over five day period at a specific temperature.
Distinguish between aerobic and anaerobic decomposition of organic material in water.
Aerobic decomp = organic material is oxidised
Anaerobic decomposition = material is reduced
Describe the process of eutrophication and its effects.
BOD increases because addition of extra nutrients (phosphates and nitrates).
Excess nutrients promotes algae and plant growth as nitrates used in protein synthesis.
Excess of nutrients known as eutrophication.
Limites oxygen = Algae death = decay increase no of nutrients.
Not enough oxygen for aerobic decomposition =
Anaerobic decomposition.
Thermal pollution
Water used as cooling agent.
Concentration of dissolved oxygen decreases with rising temperatures.
Oxygen insufficient for fish to survive – fertilisation etc sensitive to temp
List primary pollutants in waste
Water and identity sources.
Heavy metals – paints, batteries, lead pipes
Pesticides – insecticides etc
Dioxins – added to organochloro compounds when incinerated. Weed killers.
Polychlorinated biphenyls: electrical transformers
Organic matter : artificial
Fertiliser (phosphate and nitrate ions)
Primary waste water treatment
Filtration: screens and grids filter large insoluble solids
Sedimentation tank: allowed to settle – sludge is removed from bottom of tank.
Secondary treatment of waste water.
Activated sludge process: air enriched with oxygen AND bacteria bubbled through waste war. BACTERIA oxidises organic matter.
Passe through sedimentation tank – settle and removed.
80% removed.
Tertiary treatment of waste water
Heavy metal ions: removed by bubbling through carefully controlled amounts of H2S. Removed by filtration – excess H2S removed because acidic.
Phosphates: addition of calcium and aluminium ions.
Nitrates biological methods anaerobic organisms turn NO3- to N2.
Multi- stage distillation
Sea water TO fresh water.
sea water is heated – passed into evacuation chamber – boils – leaves dissolved compounds – steam passes through condenser. Cooled by pipes contains sea water. Sea water in pipes become slightly warm.
Reverse osmosis
Sea water TO fresh water
Partially permeable membrane that can withstand high temperatures.
Increase pressure so moves from
High concentration to low concentration.eaves dissolved salts behind.
Salinisation
Cause of soil degradation.
Irrigation water contains salts.
Soil is continuously irrigated – salts are deposited.
poorly drained soils = salts begin to
Accumulate in topsoil.
Excess salt = plants cannot grow
Soil degradation
Human activity reduces the capacity of soil to support life.
Nutrient depletion
Cause of soil degradation.
When plant dies – nutrients and minerals returned to soil.
Crops are harvested = nutrients removed from soil.
Soil pollution
Cause of soil degradation.
Mining / excess use of agricultural fertilisers – pesticides- Improper disposal of toxic waste.
Polluted soil – contaminated plants – contaminated food chain. Run into surface waters – polluting groundwater.
Soil organic matter
Represents organic constituents in soil, inc undecayed plant and animal tissues, their partial decomp and soil biomass.
High molecular- proteins polysaccharide
Simpler – sugars, amino acids
Physical functions of SOM
Structural stability- organic matter loosens soil increasing amount of pore space. Soil structure improves. Influences water retention- more porous therefore hold
More water and air. Black – absorbs heat and helps to warm in spring
Biological
Source of nutrients. Resilience of soil and plant system.
List common organic soil pollutants and sources
Petroleum hydrocarbons – unburnt petroleum.
Agrichemicals – pesticides weed killer insecticides
VOCs – terpenes, solvents , unburnt petroleum, anaerobic decom organic matter
PAHs
Benefits of recycling
Reduces use of raw materials.
Energy costs
Level of pollutants.
Need of land for
Waste disposal
Characteristics and sources of low level radioactive waste
Clothing, paper towels in hospitals. fuel Containers, smoke alarms
Activity is low , short half life , high volume.
High level radioactive waste
Nuclear industry : spent fuels rods. High activity, long half life, low volume.
Storage and disposal of diff types of radioactive waste.
Low level waste: stored in cooling ponds of water until activity falls to safe levels. Ions from water responsible for activity removed. – diluted and released into sea. Steel containers – concrete lined vaults.
High level: buried deep underground. Land masses may move. Potential weapon terrorist. Leak into water supply.
Outline dependence of O2 and O3 on wavelength of bond.
O2 has stronger bonds than O3 therefore O2 needs high energy, short wavelength 242= UV
O3 uv of lower energy. 330nm
Describe catalysis of O2 by CFCs and NOx
CCl2F2 – CClF2 Cl•
Cl• O3 – ClO• O2
ClO• O• – O2 Cl•
NO O3 – NO2 O2
NO2 O• – NO O2
CATALYSTS –
Not used in reactio.
Outline reasons for greater ozone depletion in polar regions
Very cold. Clouds of ice form. Ice become heterogenous catalysts – provide surface for reactants.
Explain role of ammonia in acid deposition.
Ammonia neutralises acid in atmosphere – forming ammonium salts. Slightly acidic ammonium salts (NH4)2SO4 and NH4NO3 sink to ground or washed out of atmosphere by rain.
NH4 deposits on soil = nitricification and acidification.
Common ion effect
Increase in concentration of ions = decrease in solubility of ions.
Why is it difficult to remove nitrate ions by chemical means?
Nitrate ions are soluble in water
Name two methods by which you can remove nitrate ions from water?
Biological: anaerobic organisms can turn nitrogen in nitrates to atmospheric nitrogen. Algae ponds.
Ion Exchange:
Ozone depleting equations
O3 NO ~ O2 NO2
NO2 O• ~ NO O2
Chemical equation for formation of a PAN
CH3C(O)OO• NO2 ~ CH3C(O)OONO2
H removed removed from aldehyde (free radical which needs sunlight)- and then reacted with No2
Effects of enhanced greenhouse effect
Melting glaciersof – expansion of oceans = flooding.
Drought/ increased rainfall – change crop yields.
Changes biodiversity.
Desrcibe Thermal inversion
Traps polluted air closer to ground by – increase in altitude causing increase in temp.
Advantage of landfill
Low cost. Filled ground can be reused.
State what is mean by cation exchange capacity
Amount of exchangeable cations in clay.
Explain why CEC depends on pH.
H ions displace exchangeable cations from soil. Reduces nutrients from the soil/ leached from soil
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