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

(N/A) $(i)$ Chemically,limestone is $CaCO_{3}$.
Importance of limestone:
$(a)$ It is used in the preparation of lime and cement.
$(b)$ It is used as a flux during the smelting of iron ores.
$(ii)$ Chemically,cement is a mixture of calcium silicate and calcium aluminate.
Importance of cement:
$(a)$ It is used in plastering and in the construction of bridges.
$(b)$ It is used in concrete.
$(iii)$ Chemically,plaster of Paris is $CaSO_{4} \cdot \frac{1}{2}H_{2}O$.
Importance of plaster of Paris:
$(a)$ It is used in surgical bandages.
$(b)$ It is also used for making casts and moulds.