Copper is the most noble of the first row transition metals and occurs in small deposits in several countries. Ores of copper inculcated chalcanthite (CuSO$$_4$$ . 5H$$_2$$O), atacamite (Cu$$_2$$Cl(OH)$$_3$$), cuprite (Cu$$_2$$O), copper glance (Cu$$_2$$S) and malacite (Cu$$_2$$(OH)$$_2$$CO$$_3$$). However, 80% of the world copper production comes from the ore of chalcopyrite (CuFeS$$_2$$). The extraction of copper from chalcopynite involves partial roasting, removal of iron and self-reduction.
In self-reduction, the reducing species is
Match the conversions in Column I with the type(s) of reaction(s) given in Column II. Indicate your answer by darkening the appropriate bubbles of the 4 $$\times$$ 4 matrix given in the ORS.
| Column I | Column II | ||
|---|---|---|---|
| (A) | PbS $$\to$$ PbO | (P) | roasting |
| (B) | CaCO$$_3$$ $$\to$$ CaO | (Q) | Calcination |
| (C) | ZnS $$\to$$ Zn | (R) | carbon reduction |
| (D) | Cu$$_2$$S $$\to$$ Cu | (S) | self reduction |
Native silver metal forms a water soluble complex with a dilute aqueous solution of NaCN in the presence of: