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E2 Acid Rain
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E2 Acid Rain






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    E2 Acid Rain E2 Acid Rain Presentation Transcript

    • E.2 Acid Rain
      • Acid deposition refers to acidic particles and gases that deposit or fall to earth
      • Acidic particles and vapours are deposited via two processes - wet and dry deposition.
        • Wet deposition is acid rain, the process by which acids with a pH normally below 5.6 are removed from the atmosphere in rain, snow or hail.
        • Dry deposition takes place when particles such as sulphates, nitrates, and gases (such as SO 2 and NOx), are deposited on, or absorbed onto, surfaces. The gases can then be converted into acids when they contact water.
      • 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 Origins of Acid Rain
      • Oxides of sulfur:
      • Sulfur dioxide occurs naturally from volcanoes and is produced industrially from the combustion of sulfur-containing fossil fuels and the smelting of sulfide ores.
      • S (s) + O 2 (g) -> SO 2 (g)
      • In the presence of sunlight sulfur dioxide is oxidized to sulfur trioxide
      • SO 2 (g) + ½ O 2 (g) -> SO 3 (g)
      • The oxides can react with water in the air to form sulfurous acid and sulfuric acid:
      • SO 2 (g) + H 2 O (l) H 2 SO 3 (aq)
      • SO 3 (g) + H 2 O (l) H 2 SO 4 (aq)
    • The Origins of Acid Rain
      • Oxides of nitrogen:
      • Nitrogen oxides occur naturally from electrical storms and bacterial action. Nitrogen monoxide is produced in the internal combustion engine and in jet engines.
      • N 2 (g) + O 2 (g) -> 2NO (g)
      • Oxidation to nitrogen dioxide occurs in the air.
      • 2NO (g) + O 2 (g) -> 2NO 2 (g)
      • The nitrogen dioxide then reacts with water to form nitric acid and nitrous acid:
      • 2NO 2 (g) + H 2 O (l) -> HNO 3 (aq) + HNO 2 (aq)
      • It can also be oxidized directly to nitric acid by oxygen in the presence of water:
      • 4NO 2 (g) + O 2 (g) + 2H 2 O (l) 4HNO 3 (aq)
    • Environmental Effects of Acid Rain
    • Methods to reduce the effects of acid rain
      • Removing sulfur dioxide from coal emissions using fluidized beds
      • Removing nitrogen dioxide from petrol combustion by using catalytic converters
      • Using more renewable forms of energy
      • Adding calcium oxide base (lime) to soil or water to neutralize the acid