Page 33 - Curriculum Visions Dynamic Book

acid rain: rain that is contaminated by acid gases such as sulphur dioxide and nitrogen oxides released by pollution.
alkali: a base in solution.
base: a compound that can react with
an acid in water to form a salt and water.
 Sulphur-containing exhaust gases are removed from the tall chimneys of this power station.
Sodium hydroxide as a pollution- preventing agent
Sodium hydroxide is used to neutralise weak acids. For example, it is used in the petroleum industry to remove sulphur-containing impurities such as hydrogen sulphide gas.
It is also used to remove sulphur dioxide from the exhaust gases of some power stations. This is known as “scrubbing”. The sulphur is used to make sulphuric acid.
EQUATION: Removing sulphur-containing impurities such as hydrogen sulphide from petroleum with sodium hydroxide
Hydrogen sulphide + sodium hydroxide ➪ sodium sulphide + water H2S(g) + 2NaOH(aq) ➪ Na2S(aq) + 2H2O(l)
Hydrogen
Sulphur
Sodium
Oxygen
EQUATION: Removing sulphur dioxide from power station exhausts with sodium hydroxide
Sulphur dioxide + sodium hydroxide ➪ sodium sulphite + water SO2(g) + 2NaOH(aq) ➪ Na2SO3(s) + H2O(l)
Oxygen
Hydrogen
Sodium Sulphur
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