Here are some of the pollutants from burning fuels, and where they come from:
|Carbon dioxide, CO2||Complete combustion of any fuel containing carbon atoms|
|Carbon monoxide, CO||Incomplete combustion of any fuel containing carbon atoms|
|Particulate carbon, C (soot)||Incomplete combustion of any fuel containing carbon atoms|
|Unburned hydrocarbons||Hydrocarbon fuel molecules which have not been oxidised at all|
|Sulfur dioxide, SO2||Combustion of a fossil fuel which contains sulfur impurities|
|Nitrogen oxides, NOx||Oxidation of atmospheric nitrogen inside the engine of a car, lorry, etc|
Sulfur dioxide is caused when sulfur atoms which are present in some fossil fuels are oxidised:
sulfur + oxygen → sulfur dioxide
S + O2 → SO2
Sulfur dioxide is then further oxidised in the atmosphere to sulfur trioxide, SO3. This gas dissolves in rainwater to make acid rain, which is a dilute solution of sulfuric acid, H2SO4.
The two reactions are:
sulfur dioxide + oxygen → sulfur trioxide
2SO2 + O2 → 2SO3
sulfur trioxide + water → sulfuric acid
SO3 + H2O → H2SO4
Acid rain harms and kills plants and animals, especially those that live in aquatic environments. It can also damage man-made objects like statues and buildings.
Nitrogen is not present in fuels, but the high temperatures and pressures inside a car engine can cause the nitrogen and oxygen in the air to react together to make oxides of nitrogen.
There are several compounds formed when nitrogen bonds with oxygen, but the two which are made inside engines are NO and NO2. These two pollutants are grouped together with the general formula NOx.
NOx gases can cause acid rain, and they also react in the atmosphere with other pollutants to make photochemical smog. Smog can have major health effects, causing asthma attacks and even death.
Diesel sometimes contains sulfur impurities. List the pollutants which could be produced when it is burned incompletely inside a car engine.
Carbon monoxide, particulate carbon, sulfur dioxide and nitrogen oxides.