sulfur
dioxide.S(s) + O2(g)
SO2(g)Environmental Issues.
2) Fossil fuels are burnt on a huge scale - Acid Rain.
Coal
(and to a lesser degree Oil and
Natural Gas) contain sulfur.
When they are burnt in a power
station the sulfur
oxidises
(reacts with oxygen) to form sulfur dioxide
gas.
sulfur
+ oxygen
sulfur
dioxide.
S(s) +
O2(g) SO2(g)
Sulfur dioxide gas is acidic, poisonous, and smells like burnt matches.
Sulfur
dioxide can be removed from the burnt waste
gases (called flue gases)
in the power station
chimney by wet scrubbing.
Calcium oxide (quicklime)
or calcium
carbonate (limestone)
is powdered and mixed with water and sprayed
into the chimney.
It reacts with the sulfur dioxide to produce calcium
sulfite
which can then be reacted with oxygen
to make calcium sulfate.
Calcium sulfate
(called gypsum) is used to
make plaster.
If sulfur dioxide gets into the atmosphere it
reacts with water and oxygen
in
the air to form a dilute solution of
sulfuric acid.
This sulfuric acid is the
main pollutant in acid rain.
Natural rain is slightly acidic due
to dissolved carbon
dioxide.
Natural rain has a pH of 5·5, acid rain has a
pH of 4.
The second most important pollutant in acid
rain is nitric
acid - see next
page.
Acid
rain kills trees.
It runs into rivers and gathers in lakes.
Eventually, lakes become too acidic, and plants and fish begin
to die.
Acid rain
reacts with limestone
and damages limestone buildings.
Powdered limestone or slaked lime can be
added to soils or lakes
to make them less acidic. It would be better if we could avoid or reduce
pollutant gas
emissions in the first
place.
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