September 10, 2014

IB chemistryMay 2015

1. Atomic Structure2. Periodicity3. Stoichiometry4. Bonding5. Energetics6. Kinetics7. Equilibrium8. Acid and Base9. Redox10. Organic Chemistry

Options:

E: Environmental ChemistryAnother option unit of your choice

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September 10, 2014

CalendarSunday Monday Tuesday Wednesday Thursday Friday Saturday

September

3

Term 1

Term 2

Option E: Environmental chemistry

E1 Air pollution

E2 Acid deposition

E3 Greenhouse effect

E4 Ozone depletion

E5 Dissolved oxygen in water

E6 Water treatment

E7Soil

E8 Waste

Air

Water

Solid

E1 Air Pollution

Primary Air Pollution

A primary pollutant means a chemical which is released into the environment and has some direct effect on health or the environment itself.

Secondary pollutants are usually made from the primary one and then go on to have their own effects.

How many different pollutantsdo we need to know?

September 10, 2014

Carbon Monoxide (CO)

Natural Source:

volcanic activity and bushfires

Man-made Source:

Incomplete combustion of fossil fuels in internal combustion engines of cars

Methods of Reduction:

Use of lean-burn engine, or catalytic converter.

C H8 18

Complete Combusion

Incomplete Combustion

Oxides of Nitrogen

Natural Source:

Electrical storms and biological processes Man-made Source:

At high temperatures inside internal combustion engine

N 2 + O 2 → 2 NO

Methods of Reduction:

Use of lean-burn engine, recirculation of exhaust gases or catalytic converter.

Sulfur dioxide can be oxidized in the air to also form SO3

Natural Source:

Oxidation of H 2S produced by volcanoes, and decay of organic matter

Man-made Source:

Combustion of sulfur-containing coal and smelting of sulfide ores

Methods of Reduction:

Alkaline scrubbing. Fluidized bed combustion.

Volatile Organic Compounds (VOCs) (C H ) or R-H)x y

Natural Source:

Anaerobic decomposition by bacteria

Man-made Source:

By-products of combustion in internal combustion engines; emitted from paints, cleaning supplies, building materials, furnishings

Methods of Reduction:

Catalytic converters,the use of green plants to improve air quality

Particulates:Particulates are very small solid particles or liquid acid drops that are pollutants in our atmosphere. Particulates can be made up of metals, soot, soil or dust particles.

Natural Source:

Particulates are formed as the result of forest or bush fires

Man-made Source:

by-product of many industrial processes and result from the combustion of fossil fuels in internal combustion engines.

Methods of Reduction:

Electrostatic precipitation

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Catalytic Converter

All vehicles are now equipped with catalytic converters.

They work by having a honeycomb of a rhodium/platinum catalyst through which the exhaust gases pass. This provides a surface upon which a number of different reactions take place involving primary pollutants.

1) Hydrocarbons:

Unburned hydrocarbons react with O 2 to form CO 2 and water.

2) Carbon Monoxide and Nitrogen oxides:

Lean-burn engine/Control of fuel/air ratio:

This uses a less rich fuel mixture, i.e. there is a higher oxygen to fuel ratio making it less likely that hydrocarbons remain unburned.

However, this process produces more oxides of nitrogen. So the control of balance is very important.

By creating a high air to fuel ratio, more complete combustion occurs and less CO is produced. However, this creates a situation in which more NOx– is produced. At a slightly lower air to fuel ratio, less NOx– but more CO is produced. The trick is to find the optimal air to fuel ratio.

Electrostatic precipitation:

Particulates are solid or liquid particles suspended in the air.

Particulates are passed through an electrostatic precipitator. The particles are charged by a negatively charged electrode, and as they pass through the collection plates, they are attracted to the positive walls of the plates.

Fluidized Bed Combustion:

This involves burning the coal on a bed of limestone, which removes the sulfur as calcium sulfate as the coal burns.

Fluidization allows the mixing of the sulfur-containing coal with limestone and lime, then, in reactions that are similar to those above, the contaminated sludge is removed, a mixture of clean coal and coal gas are produced and the sulfur dioxide pollutant is removed.

Before the waste gases are released out of the coal-burningpower stations, they are exposed to scrubbing with an alkaline solution of limestone and lime. The resulting sludge is used for landfill or plasterboard.

Alkaline Scrubbing:

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Acid Deposition:

Acid Rain

Why change to

from

Wet: Rain, snow, fog

Dry: Gas, particles pH of normal rainwater = ?

why?

What is the

What's Acid Rain?If rain water is acidic, then

Any form of precipitation that has a pH of less than 5.6 is considered acid deposition. The rainfall with the lowest recorded pH level—a pH of 2.4—fell in Scotland in 1974.

Common Acids:

Power generating plants and other industrial plants give off large amounts of sulfur dioxide (SO2), particulate matter and nitrogen oxides (NOx), all of which are primary pollutants. Wind and other weather patterns transport these pollutants, which eventually form secondary pollutants: nitrogen dioxide (NO2), nitric acid (HNO3) and sulfuric acid (H2SO4).

Equations!need to memorize them!

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Effects:

Vegetation: Lakes and Rivers

Buildings

Acid deposition has directly resulted in the deterioration of many historic marble structures. Marble is primarily made up of limestone (CaCO3), which reacts with sulfuric acid:

The acidity will either directly kill fish or affect their ability to successfully produce eggs or for their young to survive. This in turn limits the food supply that is available to local birds, snakes and insects whose diet is directly linked to the health of water supplies.ACID SHOCK

3. Liming (adding lime/limestone) the Lakes

2.

1.

Sun light coming in: Visible light

Light reflected out: IR

Equilibrium: light coming in = light going out

Therefore, the temperature on earth stays the same.

However, the greenhouse gases allows the visible light to come in, but absorb the IR light going out and reradiate back on the earth.

This way, light coming in > light going out.Therefore, the temperature on Earth is increasing gradually.

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CH 4: Anaerobic decay of organic matter caused by intensive farming 30 18%

H 2O: Evaporation of oceans and lakes 0.1

CO 2: Combustion of fossil fuels and biomass1 50%

N 2O: Artificial fertilizers and combustion of biomass150 6%

CFCs: Refrigerants, propellants, foaming agents, solvents10000~25000 14%

O 3: Secondary Pollutant in photochemical smogs2000 12%

Heat trapping effectiveness Overall contribution global warming

Do not just say climate change, be specific!

The Ozone Layer: Natural Formation and Depletion of Ozone = Equilibrium

Stratosphere

September 10, 2014

Oxides of nitrogen (NOx) formed from internal combustion engines, power stations, and jet aeroplanes.

The most common CFC is CFC - 12: dichlorodifluoromethane,Also known as freon, used for refrigerants, propellants for aerosols, foaming agents for expanding plastics, and cleaning solvents.

CFCs

CFCs destroy the ozone layer because the UV light breaks the relatively weak C-Cl bond.This allows the formation of Chlorine radicals which reacts with the ozone molecules.

Alternatives must have similar chemical properties but not contain a bond that can be broken by UV to form radicals.

The properties required are: low reactivity, low toxicity, and low inflammability, as well as no weak C-Cl bonds. They should not absorb IR radiation as well, or they will act as greenhouse gases.

The alternatives are: hydrocarbons, fluorocarbons, and HFCs.