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Acids and Alkalis

What are the Properties of Alkalis?

All alkalis have a pH greater than 7 and make hydroxide ions in water.

All alkalis will make litmus paper turn from red to blue
and universal indicator will turn blue or purple.

All alkalis react with acids to form a salt and water, see neutralisation.


What are the Uses of Alkalis?

1) Sodium hydroxide is used in the manufacture
of paper, soap and ceramics.
Ceramics include plates, cups, bricks and tiles.
Sodium hydroxide is used as an alkali cleaner and
to treat aluminium before anodising. Sodium
hydroxide is also used to neutralise acids to make salts.

2) Calcium oxide or calcium carbonate is used to
remove acidic gases from a power station chimney to reduce
acid rain. Calcium carbonate has many other uses.

3) Calcium hydroxide (called 'slaked lime', or just 'lime'),
is added to soils or lakes to make them less acidic
(see acid rain). Calcium hydroxide solution (lime water)
is used in the test for carbon dioxide gas.

4) Ammonia is used in the Haber process to make fertiliser.

5) Hydrochloric acid is produced in the stomach to
kill harmful bacteria that may be present on food.
Indigestion can be caused by too much (excess)
hydrochloric acid in the stomach. Indigestion tablets
contain a base such as magnesium oxide or
calcium carbonate which can neutralise the excess acid.

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