1. Environmental Chemistry: Acid Rain
Yr 10 Chemistry
Environmental Chemistry: Acid Rain

2. Give reasons for your answer
Starter
Which is the odd one out?
Give reasons for your answer
car
volcano
house

3. Objectives TO KNOW what is ‘acid rain’.
TO BE ABLE to write the balanced equations for the formation of acid rain and its reaction with limestone.
TO UNDERSTAND how acid rain leads to environmental damage.

4. Acid Rain Mind Map Definition Prevention ACID RAIN
Chemical reactions to form acid rain
Gases that cause Acid Rain
Affects of Acid Rain
Animals
Plants
Building
Humans
Chemical reactions on building materials
Man made sources

5. Acid Rain Mind Map What to include: Definition Gases Man-made sources
Chemical Reactions
Affects of Acid Rain. Plants/Animals/Humans/Buildings
Chemical reactions on Building Materials
Prevention
References (on the back)
Rates of reaction: Why does more concentrated acid in rain have a greater effect.
Rates of reaction: Why does large building blocks of building materials appear to be affected less than small blocks.

6. Environmental Chemistry
What is it? • encourages environmentally conscious behaviour
• reduces and prevents pollution
• reduces the destruction of the planet
Basics • better to prevent waste than to treat it afterwards
• aim for maximum atom economy
• use processes which require fewer chemicals
• don’t make products that are toxic to human health
• don’t make products that are toxic to the environment
• reduce the energy requirements of processes
• use alternative energy resources
• use renewable raw materials, not finite resources
• use catalysts where possible
• waste products should be designed to be biodegradable
• reduce the risk of explosions and fires

7. Man affects the Earth in many ways
Man affects the Earth in many ways. These are just some of the ways we have an effect on the Earth
Burning fossil fuels – acid rain, global warming
Open cast mining
Disposal of waste technology (mostly sent overseas)
Disposal of household waste (incineration or landfill)
Extraction of oil
Sea bed mining
Extraction of salt from the sea

8. Contents
Definition
Causes
Formation
Effects
Preventive Measures

9. Definition of Acid Rain
Precipitation that has a pH of less than that of natural rainwater (which is about 5.6 due to dissolved carbon dioxide).
It is formed when
sulfur dioxide and sulfur trioxide
nitrogen monoxide and nitrogen dioxide
Carbon dioxide
gases in the atmosphere, combine with water vapor and precipitate as sulfuric acid or nitric acid.
This acidic precipitation then falls to the earth as rain, snow, or fog.

10. Formation of Sulfuric Acid (H2SO4)
2SO2(g) + O2(g)  2SO3(g)
SO3(g) + H2O(l)  H2SO4(aq)
Formation of Nitric Acid (HNO3)
2NO(g) + O2(g)  2NO2(g)
4NO2(g) + 2H2O(l) + O2(g)  4HNO3(aq)

11. Sources OF ACID RAIN
SO2
NOX

12. Sources of Acid Rain
Natural Sources – Non-anthropogenic (not man-made)
Emissions from volcanoes and from biological processes that occur on the land, in wetlands, and in the oceans contribute acid-producing gases to the atmosphere
Effects of acidic deposits have been detected in glacial ice thousands of years old in remote parts of the globe

13. Anthropogenic Sources of Acid Rain
The principal cause of acid rain is from human sources
Industrial factories, power-generating plants and vehicles
Sulfur dioxide and oxides of nitrogen are released during the fuel burning process (i.e. combustion)
Sulfur dioxide
accounts for about
90 % of all acid
rainfall
MSN Encarta

14. Formation of Acid Rain

15. Formation of Acid Rain
When water vapor condenses, or as the rain falls, acidic gases dissolve in the water to form sulfuric acid (H2SO4) and nitric acid (HNO3).
While the air in cleaned of these acidic pollutants in this way, the resulting precipitation is acidic, and it can have serious negative effects.

17. Acidic Rain Deposition
Acidic particles and vapors are deposited via two processes - wet and dry deposition.
Wet deposition is acid rain, the process by which acids are removed from the atmosphere in rain, snow, sleet or hail.
Dry deposition takes place when particles such as fly ash, sulfates, nitrates, and gases (such as SO2 and NO), are deposited on, or absorbed onto, surfaces.
The gases can then be converted into acids when they contact water.

18. Harmful Effects of Acid Rain
Harmful to aquatic life
Increased acidity in water bodies
Stops eggs of certain organisms (e.g. fish) to stop hatching
Changes population ratios
Affects the ecosystem

19. Effects on Aquatic Life
Acidification of lakes and rivers.
One major effect on fish is the increased concentration of Al ion resulting from the leaching of soil by acid rain. Al ion affects the function of the gills.

20. Effects of Vegetation Harmful to vegetation
Increased acidity in soil
Leaches nutrients from soil, slowing plant growth
Leaches toxins from soil, poisoning plants
Creates brown spots in leaves of trees, impeding photosynthesis
Allows organisms to infect through broken leaves

22. Effect on soil and vegetation
Acute injury due to short term exposure to high acid concentrations leads to attacks on cells producing dead areas of leaves which dry out and usually become bleached.
Chronic injury due to long term exposure to even low acid concentrations disrupts chlorophyll synthesis, characterized by yellowing of leaves.
Acid rain also leaches or removes important nutrients such as magnesium ion from soil.

23.
MSN Encarta

26. Effects of Acid Rain on Buildings and Structures
Marble is particularly susceptible
Accelerates weathering in metal and stone structures
Eg. Parthenon in Athens, Greece; Taj Mahal in Agra, India
MSN Encarta

27. Effects on Materials
So the sulfate can dissolve in water leading to considerable damage to structural and artists’ stone and this is called ‘stone leprosy’
Corrosion of iron and steel
Acid rain pollution causes bleaching and weakening of fabrics and leather discoloration and embitterment of paper.
Leach heavy toxic metals such as lead, cadmium and mercury into the water system.

30. Effects of Acid Rain on Human Health
Affects human health
Respiratory problems, asthma, dry coughs, headaches and throat irritations.
Eye Irritation
Leaching of toxins from the soil by acid rain can be absorbed by plants and animals. When consumed, these toxins affect humans severely.
Brain damage, kidney problems, and Alzheimer's disease has been linked to people eating "toxic" animals/plants.

31. Effect on Visibility
The mist of sulfuric acid and sulfate aerosols in the atmosphere can cause great loss of visibility and can curtail air flights.

32. Controlling Acid Rain
Most efforts at reducing acid rain are directed at the important sources of the pollutants, namely the burning of coal and the fuelling of automobile engines.

33. Preventive Measures
Reduce amount of sulfur dioxide and oxides of nitrogen released into the atmosphere
Use less energy (hence less fuel burned)
Use cleaner fuels
Remove oxides of sulfur and oxides of nitrogen before releasing
Flue gas desulphurization
Catalytic Converters

34. Preventive Measures Use cleaner fuels Coal that contains less sulfur
"Washing" the coal to reduce sulfur content
Natural Gas

35. Preventive Measures Flue Gas Desulfurization (FGD)
Removes sulfur dioxide from flue gas (waste gases)
Consists of a wet scrubber and a reaction tower equipped with a fan that extracts hot smoky stack gases from a power plant into the tower
Lime or limestone (calcium carbonate) in slurry form is injected into the tower to mix with the stack gases and reacts with the sulphur dioxide present

36. Preventive Measures (continued)
Produces pH-neutral calcium sulfate that is physically removed from the scrubber
Sulfates can be used for industrial purposes
Scrubber at work
MSN Encarta

37. Alkaline Scrubbers

38. Preventive Measures
Use sources other than coal to generate electricity
Issue of cost
nuclear power
hydro-electricity
wind energy
geothermal energy,
solar energy

39. Reducing the effects of Acid Rain
Liming
Powdered limestone/limewater added to water and soil to neutralize acid
Used extensively in Norway and Sweden
Expensive, short-term remedy
Activity:
Show the balanced chemical equation for the reaction with acid and calcium carbonate (limestone)

40. Problem Scenario
Suppose you worked in the government. A company wants to set up a factory in your country. It would bring jobs, but it would also bring about pollution, which would lead to acid rain. Would you allow it? Justify your answer.