Environmental Chemistry Guide
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Transcript of Environmental Chemistry Guide
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Environmental Chemistry: Assessment Statement Test
This test will cover Option E in the IB Chemistry guidelines, except for a few areas of soil that still confuse even Mrs. Nagel. The following
outline sums them up!
DEFINITIONS!
1. Acid Deposition – Any combination of dry/airborne acidic particles, or precipitation, that falls to earth.Acidic here means rain pH<5.65.Natural rain is slightly acidic because of presence of CO2, which combines with H20:
CO2 + H2O -> H2CO3
2. DO – Dissolved oxygen in water.It’s an important sign of microorganic life in water, as well as an
indicator of purity and ability to sustain life.
3. BOD – Biochemical Oxygen Demand.Measure of quantity of oxygen consumed by microorganisms
during decomposition of organic matter.High BOD = Low DO
4. Eutrophication – Cycle of consumption of free phosphates/nitrates in water, leading to plant growth and death, leading to release of more phosphates/nitrates by decomposing bacteria.
Is only bad when it cycles too rapidly, leading to overpopulation of plant growth, low DO, and choked lake.
5. Aerobic decay – O2 used to break down organic matter.Results in:C -> CO2
N -> NO3-
S -> SO4-2
P -> PO4-3
6. Anaerobic decay – Organic matter decomposed oxygen-free!Results in:C -> CH4 (methane)
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N -> NH3 and aminesS -> H2SP -> PH3 (phosphine)
7. Distillation – Process by which water is heated in coiled pipes, forced to evaporate, and continues heating; all in order to prepare salt water for drinking.8. Reverse osmosis – Process by which, using high pressure, water is forced through a semi-permeable membrane in order to remove unwanted material so that the water is drinkable.
9. Humus – Mixture of simple and complex organic chemicals of plant, animal, or microbial origin. Basically, nonliving organic matter.
10. Salinization – Accumulation of salts in soil—caused by excess irrigation and poor drainage
Can lead to toxic buildups of salt, or dehydration.
11. Nutrient depletion – Over-intense absorption of nutrients—caused by constant farming of the same old plants
Can lead to total nutrient depletionuseless soil
12. Soil pollution – Presence of harmful materials in soil—caused by industrial waste, oil, and pesticides
Can reduce biodiversity and ruin soil
13. SOM – Soil Organic Matter.Organic constituents (plant or animal tissues/partially
decomposed products/soil biomass) of soilComposed of organic matter broken into a mixture of smaller
moleculesSOM can be found by titration with dichromate solutions.
14. Mineralization – Breaking down of organic matter to get nitrogen/phosphates into the roots of plants.
It ALWAYS comes back to N and P.
Importance:Biological – Creates reservoir of nutrients (N, S, and P)Physical – Soil clusters collect in stable form to reduce erosion and hold waterChemical – Increases CEC (below); acts as pH buffer; chelation
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CHELATION – Formation of complex ions from metals; removes metals from use in soil. Can be good or bad depending on the metals.
15. CEC – Cation Exchange Capacity.Extent to which negative charges in humus and clay can be
traded with nutrient cations at roots of plants. (ie. Amount of cations a soil can hold)
Indication of soil’s fertilityEnhances ability of soil to be a pH bufferRemoves toxins.
FORMULAS!
Sulfuric acid comes from: Combustion.S + O2 SO2 + H2O H2SO3
Or SO2 + ½O2 SO3 + H2O H2SO4
Nitric Acid comes from: Internal combustion.N2 + O2 2NO
Or N2 + 2O2 2NO2
NO2 + H2O HNO3 + HNO
Precipitation of Calcium by Sulfate ions:Ca+2 (aq) + SO4
-2 (aq) CaSO4 (s)
METHODS/EXPLANATIONS!
Acid Deposition: SourcesN – Internal Combustion Engines Bacterial decomposition Electrical storms
S – Volcanoes Combustion of fossil fuels Ore-smelting
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Acid Deposition: Removal/ReductionN and S – Improved Engine Design
Catalytic convertersLiming (neutralizes acidity)
S – Coal-washingStack scrubbersReduce amount burned
N – Alternative engine fuels
ALSO INVOLVED IN ACID DEPOSITION: AMMONIA
NH4+ (aq) + 2O2 (g) 2H+ (aq) + NO3
- (aq) + H2O (l)
Ammonia comes from rhizobia bacteria in soil, legumes, etc.It can neutralize acids from rain to reduce their effect. Yay!
SOIL pH: GOOD PH MEANS 6-7.5. Anything else is bad.
THREE FACTORS AFFECTING DO in water:
1. Thermal pollution/TemperatureHigh temp = Low DO
2. EutrophicationToo much anaerobic decay/overpopulation of
organisms = Low DO
3. Presence of Organic WasteToo much waste = Low DO
In general, High BOD (caused by presence of aerobic, respirating organisms) means LOW DO.
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Finally, sewage treatment. Important because it allows water to be
recycled by removing unwanted waste. Primary treatment: Simple filters remove
large waste. Secondary: trickle filters or aerobic bacteria
remove water that is bubbled with oxygen, allowing natural decomposition of waste.
Water is disinfected with Cl or Ozone. Tertiary treatment: Removes N and P from
water. More expensive, but necessary. Precipitation is used to remove metals.
C’est tout (that’s it) for the guide tonight!
Refer to pages 132, 135-138, 142, and 143 for more information.Good luck!