Describe the importance of the following: (i) limestone (ii) cement (iii) plaster of paris.

Importance of limestone
It is used in the manufacture of quick lime.
CaCO₃ --> CaO +CO₂
Quicklime, when added to water in limited amount, is used to produce slaked lime or milk of lime Ca(OH)₂
CaO +H₂O ---> Ca(OH)₂
It is used as a flux to remove acidic impurities
CaO +SiO₂ ---> CaSiO₃
6CaO + P₄O₁₀--> 2Ca₃(PO₄)₂

The importance of cement: Cement is an important building material. it is used in the concrete and reinforced concrete, in plastering and in the construction of dams, bridges and buildings.

The importance of plaster of Paris:On heating gypsum at 373 K, it loses water molecules and becomes calcium sulphate hemihydrate plaster of Paris.Plaster of Paris is a white powder and on mixing with water, it changes to gypsum once again giving a hard solid mass. It is used for immobilising the affected part where there is a bone fracture. It is used for making statues, models and other decorative materials.