1. Describe the manufacture of lime (calcium oxide) from calcium carbonate (limestone) in terms of the chemical reactions involved, and its uses in treating acidic soil and neutralising industrial waste products.

Calcium oxide (lime) is manufactured by thermally decomposing calcium carbonate (limestone):

CaCO3(s) ——-heat——->  CaO(s)   + CO2(g)
calcium carbonate ——–> calcium oxide + carbon dioxide

This takes place in a furnace called a lime kiln which rotates and the limestone is heated by current of strong hot air. Since this is a reversible reaction, the carbon dioxide produced is carried out of the kiln (so that it doesn’t react back with the calcium oxide to produce calcium carbonate). The calcium oxide is removed at the bottom of the kiln.

 

Calcium oxide (lime) is used to treat acidic soil and industrial waste in order to neutralise it. The sulfur dioxide that factories produce are reacted with calcium oxide so that it doesn’t mix with the air and cause acid rain.

 

Notes submitted by Lintha

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