Limestone
Limestone is a sedimentary rock formed by the deposit and compaction of marine organisms over time. The main material in limestone is calcium carbonate, chemical formula, CaCO3. Limestone is used as a building material and in the manufacture of cement. It is also used in blast furnaces to purify the iron and to make sodium carbonate, Na2CO3 via the Solvay process which is used in the manufacture of glass.
When limestone is strongly heated it decomposes into calcium oxide, also called quicklime and carbon dioixde gas.
Calcium carbonate =heat=> Calcium oxide and Carbon dioxide gas
CaCO3(s) =heat=> CaO(s) + CO2(g)
White limestone rock
The calcium oxide that is formed can be used to make slaked lime or calcium hydroxide.
Calcium oxide + water ==> Calcium hydroxide
CaO + H2O ==> Ca(OH)2
The reaction is extremely exothermic and produces a large amount of heat. Both calcium oxide and hydroxide are basic in nature and can be used tro neutralise acidic sulfur dioxide from the combustion of coal in coal powered electrical generator plants.