Limestone

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Marble, limestone and chalk are all made from the compound called calcium carbonate.

There are several reactions you need to know:

When calcium carbonate is heated strongly it decomposes, forming calcium oxide (lime) and releasing carbon dioxide gas.

Word equation: Calcium carbonate ---> calcium oxide + carbon dioxide

When water is added to calcium oxide heat is generated, causing steam to be released, and forming slaked lime (calcium hydroxide).

Word equation: Calcium oxide + water ---> calcium hydroxide

Calcium carbonate reacts with acids to release carbon dioxide gas.

Word equation: Calcium carbonate + hydrochloric acid ---> calcium chloride + carbon dioxide

USES
Limestone is a useful building material as it is soft and can be carved easily. Due to its softness, however, it is easily eroded by the weather. It is also attacked by the acid in rainwater and in recent years acid rain, caused by atmospheric pollution, has seriously damaged a lot of limestone buildings.

A lot of limestone is turned into lime and used in the manufacture of cement.

Because lime is alkaline it is used in agriculture to remove acid from acid soils.
It is also used in the steel industry as one of the ingredients added to a blast furnace

 

Carbon dioxide:

Properties: a colourless, odourless gas. It is more dense than air. It does not support combustion.

It is prepared in the laboratory by reacting hydrochloric acid with marble chips

Word equation: Calcium carbonate + hydrochloric acid ---> calcium chloride + carbon dioxide

 

The test for carbon dioxide gas is to bubble it through limewater which will turn milky.

It is used on fizzy drinks and in fire extinguishers.

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