Chapter 17 Section F: Acid Rain

- Every year, acid rain causes hundreds of millions of dollars' worth of damage throughout the world
- It damages stone buildings and statues and is toxic to vegetation and aquatic life
- The average pH of rain in the northeastern US is 4.3
- Atmospheric CO2 alone could only cause the pH to drop to ~5.5, so SO2 must also be present
- Sources of SO2: * burning of fossil fuels in industry, power plants, and homes
---------------------------* smelting (extracting) metals
---------------------------* 2ZnS(s) + 3O2(g) 2ZnO(s) + 2SO2(g)
---------------------------* volcanoes
- 50 to 60 million tons of SO2 are released into the atmosphere every year
- SO2 is oxidized to H2SO4 through a complex process that is not well understood:
- OH + SO2 HOSO2
- HOSO2 + O2 HO2 + SO3
- SO3 + H2O H2SO4
- Acid rain can corrode limestone and marble (CaCO3):
- CaCO3(s) + H2SO4(aq) CaSO4(s) + H2O(l) + CO2(g)
- Sulfur dioxide can directly attack calcium carbonate:
- 2CaCO3(s) + 2SO2(g) + O2(g) 2CaSO4(s) + 2CO2(g)
- Acid rain is also caused by carbon monoxide, chlorofluorocarbons, lead, nitrogen oxides, ozone,
- particulate matter, and volatile organic compounds

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