Page 23 - Curriculum Visions Dynamic Book

acidity: a general term for the strength of an acid in a solution.
smoke: a mixture of both small solids and gases.
Electrostatic precipitators
Many new power stations are being
built with electrostatic precipitators
built into the chimney system. An electrostatic precipitator uses static electrical charges to cause sulphur particles to be precipitated from the
flue gases. This leaves the exhaust cleaner and less liable to cause acid rain. The sulphur collected can be used for other purposes (see pages 18 and 19), thus offsetting the cost of the equipment.
 These are electrostatic precipitators fitted to a new 1000 megawatt power station in India to remove the sulphur from the exhaust gases. The electrostatic precipitators are in the foreground of the picture.
EQUATION: Removing sulphur dioxide from power station exhausts with sodium hydroxide
Sulphur dioxide + sodium hydroxide ➪ sodium sulphate + water SO2(g) + 2NaOH(aq) ➪ Na2SO3(s) + H2O(l)
◆
+➡◆+
Hydrogen
Sodium
Sulphur
Oxygen
◆
Pollution that crosses borders
Sulphur dioxide is a gas, so it can be carried large distances from where it is produced. This means that, for example, sulphur dioxide released by power stations in one place can be carried thousands of kilometres downwind, where it might combine with water droplets in a cloud and cause acid rain that harms trees.
In the most extreme cases, pollution caused in one country can cause acid rain damage in another country. This is most likely to be the case in both Europe and North America. In Europe the coals used in power stations in eastern Europe have produced pollution that has killed trees in the Black Forest of Germany; pollution produced in Britain may have harmed forests in Norway and Sweden; and pollution from the northeastern United States and southeastern Canada has harmed forests in eastern North America.
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