E2 Acid Rain

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E2 Acid Rain

  1. 1. E.2 Acid Rain
  2. 2. <ul><li>Acid deposition refers to acidic particles and gases that deposit or fall to earth </li></ul>
  3. 3. <ul><li>Acidic particles and vapours are deposited via two processes - wet and dry deposition. </li></ul><ul><ul><li>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. </li></ul></ul><ul><ul><li>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. </li></ul></ul><ul><li>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. </li></ul>
  4. 7. The Origins of Acid Rain <ul><li>Oxides of sulfur: </li></ul><ul><li>Sulfur dioxide occurs naturally from volcanoes and is produced industrially from the combustion of sulfur-containing fossil fuels and the smelting of sulfide ores. </li></ul><ul><li>S (s) + O 2 (g) -> SO 2 (g) </li></ul><ul><li>In the presence of sunlight sulfur dioxide is oxidized to sulfur trioxide </li></ul><ul><li>SO 2 (g) + ½ O 2 (g) -> SO 3 (g) </li></ul><ul><li>The oxides can react with water in the air to form sulfurous acid and sulfuric acid: </li></ul><ul><li>SO 2 (g) + H 2 O (l) H 2 SO 3 (aq) </li></ul><ul><li>SO 3 (g) + H 2 O (l) H 2 SO 4 (aq) </li></ul>
  5. 8. The Origins of Acid Rain <ul><li>Oxides of nitrogen: </li></ul><ul><li>Nitrogen oxides occur naturally from electrical storms and bacterial action. Nitrogen monoxide is produced in the internal combustion engine and in jet engines. </li></ul><ul><li>N 2 (g) + O 2 (g) -> 2NO (g) </li></ul><ul><li>Oxidation to nitrogen dioxide occurs in the air. </li></ul><ul><li>2NO (g) + O 2 (g) -> 2NO 2 (g) </li></ul><ul><li>The nitrogen dioxide then reacts with water to form nitric acid and nitrous acid: </li></ul><ul><li>2NO 2 (g) + H 2 O (l) -> HNO 3 (aq) + HNO 2 (aq) </li></ul><ul><li>It can also be oxidized directly to nitric acid by oxygen in the presence of water: </li></ul><ul><li>4NO 2 (g) + O 2 (g) + 2H 2 O (l) 4HNO 3 (aq) </li></ul>
  6. 9. Environmental Effects of Acid Rain
  7. 10. Methods to reduce the effects of acid rain <ul><li>Removing sulfur dioxide from coal emissions using fluidized beds </li></ul><ul><li>Removing nitrogen dioxide from petrol combustion by using catalytic converters </li></ul><ul><li>Using more renewable forms of energy </li></ul><ul><li>Adding calcium oxide base (lime) to soil or water to neutralize the acid </li></ul>

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