Match the reactions given in column(I) with the appropriate method(s) listed in column (II).
`{:("Column-I","Column-II"),((A)4 Au+8 NaCN+ 2 H_2O+O_2("air")to4 Na[Au(CN)_2]+4NaOH,(p)"Leaching"),((B)CuFeS_2+2 H_2SO_4toCuSO_4+FeSO_4+2 H_2O,(q)"Smelting"),(( C)Fe_2O_4+4 COoverset(823K)to3 Fe+4CO_2,(r)"Roasting"),((D) MgCl_2. 6H_2O underset("Dry" HCl(g))overset(Delta)toMgCl_2+6H_2O,(s)"Calcination"),(" ",(t)"Hydrometallurgy"):}`

Answer

A`to`p,t ; B`to`p,t ; C`to` q ; D`to`s

Explanation

(A)Gold dissolves in NaCN solution forming a soluble complex leaving behind impurities is called leaching process. Hence the extraction of gold is called hydrometallurgy.
(B)Insoluble copper pyrites dissolves in `H_2SO_4` forming soluble `CuSO_4` is called leaching. Hence the extraction of copper is called hydrometallurgy
(C )Reduction of `Fe_3O_4` by CO in blast furnace is smelting.
(D)Heating `MgCl_2 6H_2O` in dry HCl gas to convert into anhydrous `MgCl_2` is calcination.