State the reason why
(i) carbon is not used to reduce the oxides of sodium or aluminium.
(ii) an iron strip dipped in a blue copper sulphate solution turns the blue solution to pale green.
(iii) calcium does not occur in free state in nature.
(iv) zinc is used in the galvanisation of iron and not copper.

Explanation

(i) Both sodium and aluminium are stronger reducing agents than carbon. Therefore, carbon is not in a position to reduce the oxides of these metals to the metallic form.
(b) Iron displaces copper from copper sulphate solution to form iron sulphate which imparts pale green colour to it.
(iii) Calcium (Ca) is a reactive metal and is placed high in the activity series. It therefore, does not exist in free state also called native state.
(iv) Zinc is placed above iron in the activity series. When deposited over its surface (galvanisation), zinc gets corroded and not iron. But copper is placed below iron and therefore, does not participate the corrosion. In this case, iron is corroded or rusted.