Pollution

• When is carbon made?

  In the engine of a car, oxygen supply is limited (CO, C, H2O, other unburned hydrocarbons also made)
• Why are oxides of nitrogen formed?

  Very high temperatures inside a car engine
• How is nitric acid (acid rain) formed?

  NOx reacts with water vapour and oxygen to form nitric acid (acid rain and photochemical smog)
• How can these pollutants be removed from the exhaust fumes of a car?

  A catalytic converter- these contain a ceramic honeycomb coated with platinum, palladium or rhodium to give a large surface area
• What happens if a hydrocarbon containing sulfur is burnt (coal)?

  SO2 is formed and oxidised into SO3 in the atmosphere and contributes to acid rain.
• Often gases produced by combustion of alkanes are released into the air through large chimneys called...

  flues (flue gas)
• How can acidic SO2 be removed from these flue gases?

  By lining the chimney's with bricks containing basic calcium oxide or calcium carbonate (flue gas desulfurisation).
• Why does acid rain happen?

  NOx and SOx can oxidise and dissolve in water to form acids. These can lower pH of lakes, destroy plant life and damage limestone buildings.
• What are greenhouse gases?

  CO2, CH4 and water vapour
• How do greenhouse gases work?

  They trap the Earth's infra-red energy- longer wavelengths
• Why has CO2 in atmosphere risen to 440ppm?

  Increasing burning of fossil fuels.
• What is Ozone depletion caused by?

  Caused by C-Cl bonds in chlorofluorocarbons to break
• Why is Ozone important?

  To protect us from harmful UV radiation
• What is the overall equation for decomposition of ozone?

  2 O3 -> 3 O2