GCSE SCIENCE CHEMISTRY HIGH SCHOOL - Manufacture and Uses of Lime - Quicklime - Slaked Lime

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Rock Products and Uses - Limestone.

Manufacture and uses of Lime.
The name "lime" is used for both calcium oxide (quicklime),
and calcium hydroxide (slaked lime).

When limestone (calcium carbonate) is heated at about 1000 °C,
it undergoes thermal decomposition,
it loses carbon dioxide and turns into quicklime (calcium oxide).

calcium carbonate calcium oxide + carbon dioxide.
CaCO₃_(s) CaO_(s) + CO₂_(g)

The reaction is carried out in specially constructed lime kilns,
(a kiln is a high temperature oven).
Limestone is added at the top,
and quicklime is removed from the bottom in a continuous process.
The same reaction occurs in the blast furnace.

Quicklime reacts with water to form slaked lime (calcium hydroxide).
The reaction is highly exothermic.

calcium oxide + water calcium hydroxide.
CaO_(s) + H₂O_(l) Ca(OH)_2(s)

Slaked lime is used to reduce the acidity of lakes and soils, see acid rain.
It acts faster than powdered limestone but is more expensive.
Slaked lime dissolves a little in water to form lime water.

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