F.5 Chemistry

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• F.5 Chemistry
• Acid Rain

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• Distribution of Work

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• Target audience
• F.5 chemistry students
• Average ability
• Purposes
• Introduce acid rain by lecturing
• Provide QA section for evaluation

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WHAT IS ACID RAIN?

• Generally, rain water has a pH value of 5.6
  because of the carbon dioxide from air dissolved
  in it
• Any rainfall has a pH value less than 5.6 is
  defined as acid rain

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• When gas pollutants e.g. sulphur dioxide,
  nitrogen dioxide dissolve in rain water, various
  acids are formed.

CO2 H2O ? H2CO3 (carbonic acid) SO2
H2O ? H2SO3 (sulphorous acid) NO2 H2O ? HNO2
(nitrous acid) HNO3 (nitric acid)
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CAUSES OF ACID RAIN
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Formation of Sulphuric 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)
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FORMATION OF ACID RAIN
SO2 NOX
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ENVIRONMENTAL PROBLEMS

• 1.Vegetation
• Wash away essential nutrients ions from soil
• Poor growth of plants

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2.Aquatic Life

• Inflow of acidic water containing poisonous metal
  ions
• Kill the fish and water plants

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3. Building

• Acid rain attacks the building materials and
  causes corrosion.

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Question and Answer

• 1. What is an acid rain?
• 2.What is the main air pollutants for the
  formation of acid rain?

Answer
Answer
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• 3.What is the pH range for the acid rain?
• 4.What are the major sources of air pollutants?

Answer
Answer
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5.What is the side effect of acid rain on
plants? 6. What is the side effect of acid
rain on marine life?
Answer
Answer
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• 7. What is the side effect of acid rain on
  building material?

Answer
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On-line References

• http//igc.apc.org/acidrain/
• http//beakman.com/acid/acid.html
• http//qlink.queensu.ca/4lrm4/

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Answer

• 1. Acid Rain is rain water with pH value less
  than 6. This is the rainfall with acidity level
  beyond what is expected in unpolluted rainfall
• 2. The main air pollutants are sulphur dioxide
  and nitrogen dioxide.
• SO2 NO2

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Answer

• 3. The unpolluted rain water is slightly acidic
  with pH about 5.6 because carbon dioxide in the
  air dissolves in rain water to form a weak acid.
  So, the pH of acid rain water is below 5.6.

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Answer

• 4. The major sources were motor vehicles,
  factories and power stations.
• 5. Acid rain makes soils become acidic. When
  the soil becomes acidic, the plant will not grow
  well.

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Answer

• 6. When acid rain runs into rivers or lakes, the
  pH value of water will goes down below 5. The
  aquatic life in water may die because of this.

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Answer

• 7. Most building materials made of limestone and
  marble. The acid rain water mainly sulphuric acid
  will react with calcium carbonate from limestone
  and marble to form calcium sulphate.

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• F.5 Chemistry
• Acid Rain