F.5 Chemistry Acid Rain

Distribution of Work

Target audience: F.5 chemistry students Average abilityPurposes: Introduce acid rain by lecturing Provide Q&A section for evaluation

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

When gas pollutants e.g. sulphur dioxide, nitrogen dioxide dissolve in rain water, various acids are formed. CO 2 + H 2 O  H 2 CO 3 (carbonic acid) SO 2 + H 2 O  H 2 SO 3 (sulphorous acid) NO 2 + H 2 O  HNO 2 (nitrous acid) + HNO 3 (nitric acid)

CAUSES OF ACID RAIN

Formation of Sulphuric Acid (H 2 SO 4 ) 2SO 2 (g) + O 2 (g) 2SO 3 (g) SO 3 (g) + H 2 O(l)H 2 SO 4 (aq) Formation of Nitric Acid (HNO 3 ) 2NO(g) + O 2 (g) 2NO 2 (g) 4NO 2 (g) + 2H 2 O(l) + O 2 (g) 4HNO 3 (aq)

FORMATION OF ACID RAIN SO 2 NO X

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

2.Aquatic Life Inflow of acidic water containing poisonous metal ions Kill the fish and water plants

3. Building Acid rain attacks the building materials and causes corrosion.

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

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

5.What is the side effect of acid rain on plants? 6. What is the side effect of acid rain on marine life?

7. What is the side effect of acid rain on building material?

On-line References

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. SO 2 NO 2

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.

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. 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.

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.

F.5 Chemistry Acid Rain