Page 134 - ICSE Chemistry 8

• Again add a drop of dilute hydrochloric acid.
You will observe that the solu on again becomes colourless.

Conclusion: The stage when the base is completely neutralised by the acid is the neutralisa on point, i.e.,
when the solu on becomes colourless.

Importance of Neutralisation Reactions in Our Daily Life

Acidity: Hydrochloric acid, also known as the gastric acid present in the
stomach, helps in the diges on of food. However, excess of hydrochloric
acid causes a painful condi on called acidity and indiges on.

Such a condi on can be overcome by taking antacids like milk of
magnesia, which is a mild base and contains magnesium hydroxide
[Mg(OH) ]. It thus neutralises the excess of hydrochloric acid.
2
(a) Ant sting
Ant and Bee S ng: When an ant or a bee s ngs, formic acid is injected
into the body which causes itching.

To neutralise the eff ect of an ant or a bee s ng, baking soda solu on
or calamine solu on is applied on the aff ected area. Baking soda
contains sodium hydrogen carbonate and calamine solu on contains
zinc hydroxide. Both these solu ons are basic in nature and hence help
to reduce the itching.
(b) Bee sting
Soil Treatment: Farmers use fer lisers to improve crop yield. Due to
Fig. 6.1: Sting aff ected areas
excessive use of fer lisers, the soil becomes either too acidic or too
basic thus preven ng proper growth of plants.

If the soil is too acidic, it can be treated with bases like quicklime which contains calcium oxide or slaked
lime which contains calcium hydroxide to neutralise its acidic nature.

Disposal of Factory Wastes: The wastes released from the factories are
acidic in nature. If they are allowed to fl ow as it is into the water bodies,
they can cause huge damage to aqua c plants and animals.

Therefore, basic substances are added to factory wastes to neutralise
their acidic nature. They are then released into the water bodies.

Redox Reaction Fig. 6.2: Factory waste

A chemical reac on in which oxida on and reduc on take place simulta neously is called a redox reac on.

Oxida on: The addi on of oxygen or the removal of
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hydrogen from a substance is called oxida on.
• Addi on of oxygen: Magnesium reacts with oxygen Many toothpastes that we use contain
to form magnesium oxide. bases to neutralise the acids formed in
the mouth.

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