Howard Lovejoy's IB Chemistry II
Environmental Chemistry

 

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1. Air pollution

1.1

Describe the main sources of carbon monoxide (CO), oxides of nitrogen (NOx), oxides of sulfur (SOx), particulates and volatile organic compounds (VOCs) in the atmosphere. Include both natural and anthropogenic sources. Equations should be used as appropriate. 1. Air pollution ppt (as pdf)
2. Read section 18.4
1.2 Evaluate current methods for the reduction of air pollution. Examples include: • CO—catalytic converters • NOx—catalytic converters, control of fuel/air ratio • SOx—alkaline scrubbing, limestone-based fluidized beds • particulates—electrostatic precipitation • VOCs—catalytic converters. 1. See handout
2. Acid Deposition

2.1

State what is meant by the term acid deposition and outline its origins. Acid deposition refers to the process by which acidic particles, gases and precipitation leave the atmosphere. Both wet deposition (acid rain, fog and snow) and dry deposition (acidic gases and particles) will be assessed. Rain is naturally acidic because of dissolved CO2 but acid rain has a pH of less than 5.6. It is caused by oxides of sulfur and oxides of nitrogen. The equations for the burning of sulfur and nitrogen, and for the formation of H2SO3, H2SO4, HNO2 and HNO3, will be assessed. 1. Acid rain ppt (as pdf)
2. Read page 712

2.2

Discuss the environmental effects of acid deposition and possible methods to counteract them.
3. Greenhouse Gases

3.1

Describe the greenhouse effect. Greenhouse gases allow the passage of incoming solar short-wavelength radiation but absorb the longer-wavelength radiation from the Earth. Some of the absorbed radiation is re-radiated back to Earth. 1. Global warming ppt (as pdf)

3.2

List the main greenhouse gases and their sources, and discuss their relative effects. The greenhouse gases to be considered are CH4, H2O, CO2, N2O and chlorofluorocarbons (CFCs). Their effects depend on their abundance and their ability to absorb heat radiation.

3.3

Discuss the influence of increasing amounts of greenhouse gases on the atmosphere. Examples include: thermal expansion of the oceans, melting of the polar ice-caps, floods, droughts, changes in precipitation and temperature, changes in the yield and distribution of commercial crops, and changes in the distribution of pests and disease-carrying organisms.
4. Ozone depletion
4.1 Describe the formation and depletion of ozone in the stratosphere by natural processes. 1. Ozone depletion ppt (as pdf)
2. Section 18.3
4.2 List the ozone-depleting pollutants and their sources. Examples include chlorofluorocarbons (CFCs) and oxides of nitrogen (NOx).
4.3 Discuss the alternatives to CFCs in terms of their properties. Alternatives include hydrocarbons, fluorocarbons and hydrofluorocarbons (HFCs). Include toxicity, flammability, the relative weakness of the C–Cl bond and the ability to absorb infrared radiation.
5. Dissolved Oxygen in Water
5.1 Outline biochemical oxygen demand (BOD) as a measure of oxygen-demanding wastes in water.
5.2 Distinguish between aerobic and anaerobic decomposition of organic material in water. Use redox equations as appropriate.
5.3 Describe the process of eutrophication and its effects.
5.4 Describe the source and effects of thermal pollution in water.
6. Water treatment
5.1 List the primary pollutants found in waste water and identify their sources. Examples include heavy metals, pesticides, dioxins, polychlorinated biphenyls (PCBs), organic matter, nitrates and phosphates. 1. Read pages 722 - 727
5.2 Outline the primary, secondary and tertiary stages of waste water treatment, and state the substance that is removed during each stage. For primary treatment, filtration and sedimentation should be covered. For secondary treatment, mention the use of oxygen and bacteria (for example, the activated sludge process). Include the removal of heavy metals, phosphates and nitrates by chemical or biological processes.
5.3 Evaluate the process to obtain fresh water from sea water using multistage distillation and reverse osmosis. 1. Read pages 719 - 720
7. Soil
6.1 Discuss salinization, nutrient depletion and soil pollution as causes of soil degradation.
6.2 Describe the relevance of the soil organic matter (SOM) in preventing soil degradation, and outline its physical and biological functions.
6.3 List common organic soil pollutants and their sources. Examples should include petroleum hydrocarbons, agrichemicals, volatile organic compounds (VOCs), solvents, polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organotin compounds and semi-volatile organic compounds (SVOCs).
8. Waste
8.1 Outline and compare the various methods for waste disposal. Examples include landfills and incineration.
8.2 Describe the recycling of metal, glass, plastic and paper products, and outline its benefits.
8.3 Describe the characteristics and sources of different types of radioactive waste. Include both low-level and high-level radioactive waste.
8.4 Compare the storage and disposal methods for different types of radioactive waste.
Higher Level Only
9. Ozone Depletion
9.1 Explain the dependence of O2 and O3 dissociation on the wavelength of light. 1. Ozone depletion ppt (as pdf)
2. Section 18.2 and 18.3
9.2 Describe the mechanism in the catalysis of O3 depletion by CFCs and NOx.
9.3 Outline the reasons for greater ozone depletion in polar regions. Consider the seasonal variation in temperature in the upper atmosphere. Refer to surface catalysis on ice particles.
10. Smog
10.1 State the source of primary pollutants and the conditions necessary for the formation of photochemical smog. VOCs and NOx, temperature inversion, windlessness and bowl-shaped cities should be discussed. 1. Air pollution ppt (as pdf)
10.2 Outline the formation of secondary pollutants in photochemical smog. Examples include NO2, O3, aldehydes and peroxyacylnitrates (PANs). The role of free radicals and sunlight should be emphasized.
11. Acid Deposition
11.1 Describe the mechanism of acid deposition caused by the oxides of nitrogen and oxides of sulfur. 1. Acid rain ppt (as pdf)
11.2 Explain the role of ammonia in acid deposition. In the atmosphere, ammonia neutralizes the acids formed to a large extent, to form ammonium salts. Slightly acidic ammonium salts, (NH4)2SO4 and NH4NO3, formed in the atmosphere sink to the ground or are washed out of the atmosphere with rain. As NH4 + is deposited and enters the soil, nitrification and acidification can occur.
12. Water and Soil
12.1 Solve problems relating to the removal of heavy-metal ions, phosphates and nitrates from water by chemical precipitation. Given the equilibrium formed by a metal M and a non-metal X:

The Keq for this system is given by
Ksp = [M+][X-], and is called the solubility product constant. Students should be able to solve problems associated with this type of equilibrium, including the common ion effect.
1. Ksp is an equilibrium expression and is discussed in section 17.4 of your textbook.
2. The common ion effect is in section 17.5.
12.2 State what is meant by the term cation-exchange capacity (CEC) and outline its importance. The amount of exchangeable cations in a clay is called cation-exchange capacity. Include equations as appropriate.
12.3 Discuss the effects of soil pH on cation-exchange capacity and availability of nutrients. Examples of nutrients include Ca, Mg, Fe, Al, P, N, S, Cu and Zn. Use equations as appropriate.
12.4 Describe the chemical functions of soil organic matter (SOM). Include the following. • Contributes to cation-exchange capacity • Enhances the ability of soil to buffer changes in pH • Binds to organic and inorganic compounds in soil • Reduces the negative environmental effects of pesticides, heavy metals and other pollutants by binding contaminants • Forms stable complexes with cations