(a) describe the volume composition of gases present in dry air as being approximately 78% nitrogen, 21% oxygen and the remainder being noble gases (with argon as the main constituent) and carbon dioxide

(b) name some common atmospheric pollutants, e.g. carbon monoxide; methane; nitrogen oxides (NO and NO2); ozone; sulfur dioxide; unburned hydrocarbons

(c) state the sources of these pollutants as

(i) carbon monoxide from incomplete combustion of carbon-containing substances

(ii) nitrogen oxides from lightning activity and internal combustion engines

(iii) sulfur dioxide from volcanoes and combustion of fossil fuels

(d) describe the reactions used in possible solutions to the problems arising from some of the pollutants named in (b)

(i) the redox reactions in catalytic converters to remove combustion pollutants (see also 6.1(d))

(ii) the use of calcium carbonate to reduce the effect of ‘acid rain’ and in flue gas desulfurisation

(e) discuss some of the effects of these pollutants on health and on the environment

(i) the poisonous nature of carbon monoxide

(ii) the role of nitrogen dioxide and sulfur dioxide in the formation of ‘acid rain’ and its effects on respiration and buildings

(f) discuss the importance of the ozone layer and the problems involved with the depletion of ozone by reaction with chlorine-containing compounds, chlorofluorocarbons (CFCs)

(g) describe the carbon cycle in simple terms, to include

(i) the processes of combustion, respiration and photosynthesis

(ii) how the carbon cycle regulates the amount of carbon dioxide in the atmosphere

(h) state that carbon dioxide and methane are greenhouse gases and may contribute to global warming, give the sources of these gases and discuss the possible consequences of an increase in global warming.