(a) Write the balanced chemical equations for the extraction of copper metal from its ore. What is the reducing agent used ?
(b) Which reducing agent can be used in the extraction of metals placed at the top of the reactivity series ? Give the name of the process also.
(c ) What is the chemical substance formed as green coating when copper reacts with atmospheric gases in moist conditions ?

Explanation

(a) Copper is isolated from its sulphide ore known as copper glance `(Cu_(2)S)` by heating with excess of air or oxygen.
`2Cu_(2)S(s) + 3O_(2)(g) overset("heat")rarr 2Cu_(2)O(s) + 2SO_(2)(g)`
`2Cu_(2)O(s) + Cu_(2)S(s) overset("heat")rarr6Cu(s) + SO_(2)(g)`
Cuprous oxide `(Cu_(2)O)` acts as reducing agent and this process is known as auto-reduction.
These metals (K, Na, Mg etc.) can be isolated by carrying out the process of electrolysis (electrolytic reduction) from their molten salts.
(c ) The green coating is of basic copper carbonate. It is formed as follows :
`2Cu + underset(("Present in air"))ubrace(H_(2)O + CO_(2)+O_(2)) rarrunderset("Basic copper carbonate")(Cu(OH)_(2).CuCO_(3))`