Page 17 - Curriculum Visions Dynamic Book

 Part of a water treatment plant.
disinfectant: a chemical that kills bacteria and other microorganisms.
neutralisation: the reaction of acids and bases to produce a salt and water. The reaction causes hydrogen from
the acid and hydroxide from the base to be changed to water. For example, hydrochloric acid reacts with sodium hydroxide to form common salt and water. The term
is more generally used for any reaction where the pH changes towards 7.0, which is the pH of a neutral solution.
precipitate: tiny solid particles formed as a result of a chemical reaction between two liquids or gases.
Chlorine
EQUATION: The reaction of chlorine and water
Water + chlorine ➪ hypochlorous acid + hydrochloric acid H2O(l) + Cl2(g) ➪ HOCl(aq) + HCl(aq)
Hydrogen
+Oxygen➡ +
The chlorination of swimming pools
Disinfectants are needed in swimming pool water to prevent the growth of bacteria and algae that might eventually become a health risk.
Chlorine gas was the disinfectant traditionally used in public baths.
It was also sold as a solid compound for domestic swimming pools.
The chlorine reacts with the water
to form hypochlorous acid, which
in turn kills bacteria and algae.
Adding more and more chlorine causes the acidity of the water to
rise, and this can have harmful side effects, such as making the eyes smart. So to prevent this, a neutralising chemical, sodium carbonate, is added.
The chlorine smell in a swimming pool is not the chlorine itself, but the smell of ammonia-like gases released
as the chlorine gets to work on
organic matter.
Disinfectants are now available without the side-effects caused by chlorine.
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