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O-Level Maintaining Air Quality
the composition of air, common pollutants, and their effects on health and the environment
What the syllabus expects
- Give the approximate composition of dry air by volume as roughly 78% nitrogen, 21% oxygen, with the remainder being noble gases (argon chiefly) and carbon dioxide.
- Name some common atmospheric pollutants, such as carbon monoxide, methane, nitrogen oxides (NO and NO2), ozone, sulfur dioxide and unburned hydrocarbons.
- Give the origins of these pollutants: carbon monoxide arising when carbon-containing matter burns incompletely, nitrogen oxides from lightning and vehicle engines, and sulfur dioxide from volcanoes and the burning of fossil fuels.
- Outline the reactions behind some possible remedies for these pollutant problems: the redox processes inside catalytic converters that clear combustion pollutants, and using calcium carbonate to lessen 'acid rain' and in flue-gas desulfurisation.
- Discuss some effects of these pollutants on health and the environment, including the toxicity of carbon monoxide and the part nitrogen dioxide and sulfur dioxide play in forming 'acid rain', which affects respiration and buildings.
- Discuss why the ozone layer is important and the problems of its depletion by reaction with chlorine-containing compounds, the chlorofluorocarbons (CFCs).
- Outline the carbon cycle in simple terms, including the processes of combustion, respiration and photosynthesis and how the cycle keeps atmospheric carbon dioxide in check.
- Note that methane and carbon dioxide count as greenhouse gases which may contribute to global warming; identify their sources and set out the likely effects of their increasing levels, such as more extreme weather and melting polar ice.
How it's examined
About 3% of the past-paper style questions in Rae's bank for this subject sit in this topic.
More O-Level Pure Chemistry topics
Experimental Chemistry · The Particulate Nature of Matter · Chemical Bonding and Structure · Chemical Calculations · Acid-Base Chemistry · Qualitative Analysis · all of O-Level Pure Chemistry