Extraction of the Metals

S. No.	Metal	Extraction of the Metal / Metallurgy
1	Copper,       Cu	1) Chief ore : Copper pyrites, CuFeS2 2) Concentration : By Froth floatation process 3) Roasting : Volatile impurities S, P, As and Sb are removed as their oxides             S + O2 → SO2            P4 + 5O2 → 2P2O5            4As + 3O2 → 2AsO3    Copper pyrites are partly converted into Sulphides of Cu & Fe        2CuFeS2 + O2 → Cu2S + 2FeS + SO2 (Major Reaction)         2FeS + O2 → 2 FeO + 2SO2  (Minor Reaction) 4) Smelting :           2FeS + 3O2     → 2FeO + 2FeO + 2SO2           FeO + SiO2      → FeSiO3 (slag)           2Cu2S + 3O2   → 2 Cu2O + 2SO2           Cu2O + FeS    → Cu2S + FeO           FeO + SiO2    → FeSiO3 (slag) 5) Bessemerisation :           2 Cu2S + 3O2    → 2 Cu2O + 2 SO2           2 Cu2O + Cu2S  → 6 Cu + SO2           Blister copper contains 98 % Copper 6) Purification : Electrolytic Refining           Anode (+)    : Impure Cu           Cathode (–) : Pure Cu           Electrolyte   : CuSO4 + dil. H2SO4        On passing current, pure Cu is deposited at the Cathode.
2	Chromium,      Cr	1) Chief ore : Chromite (or) Chrome ore, FeO.Cr2O3 2) Concentration : By Gravity separation process 3) Conversion of concentrated Chromite ore into Na2CrO4 (Roasting)                                                      900 – 1000oC      4(FeO.Cr2O3) + 8Na2CO3 + 7O2 (from air) ------------>                                           8Na2CO3 + 2Fe2O3 + 8CO2                                           Soluble       Insoluble 4) Conversion of Na2CrO4 into Na2Cr2O7        2Na2CrO4 + H2SO4 → Na2Cr2O7 + Na2SO4 + H2O 5) Conversion of Na2Cr2O7 into Cr2O3 (Reduction of the dichromate)        Na2Cr2O7 + 3C →  Na2Cr2O4 + 3CO↓        Na2Cr2O4 + H2O → 2NaOH + Cr2O3↓ 6) Reduction of Cr2O3 into Cr : Alumino thermic process         Diagram with labels      Cr2O3 is reduced with Al powder (3:1)      Ignition mixture : BaO2 + Mg powder       The mixture is ignited by a piece of Mg ribbon      Cr2O3 + 2Al → 2Cr + Al2O3 + 468.6 kJ                                          (slag)
3	Zinc,    Zn	1) Chief ore : Zinc blende, ZnS 2) Concentration : By Froth Floatation process 3) Roasting : 2ZnS + 3O2 1200 K→ 2ZnO + 2SO2 4) Reduction : ZnO + C 1673 K→ Zn + CO 5) Purification : Electrolytic Refining      Anode (+)    : Impure Zn      Cathode (–) : Pure Zn      Electrolyte  : ZnSO4 + dil. H2SO4        On passing current pure Zn gets deposited on the Cathode
4	Silver,      Ag	1) Chief ore : Argentite (or) Silver glance, Ag2S 2) Concentration : By Froth floatation process 3) Treatment of the concentrated ore with NaCN: Mac Arthur Forrest’s Cyanide process       Ag2S + 4NaCN → 2 Na[Ag(CN)2] + Na2S 4) Precipitation of Silver      2Na[Ag(CN)2] + Zn → 2Ag↓ + Na2[ Zn(CN)4 ] 5) Purification : Electrolytic Refining      Anode (+)   : Impure Ag      Cathode (–) : Pure Ag       Electrolyte : AgNO3 + 1% HNO3     On passing electricity pure Ag gets deposited at the Cathode.
5	Gold,        Au	1) Chief ore : Sulphide (or) Telluride ore. 2) Concentration : By Froth floatation process 3) Roasting : Volatile impurities S, As and Te are removed as their oxides. 4) Treatment of the concentrated ore with KCN: Mac Arthur Forrest Cyanide process      4 Au + 8KCN + 2H2O + O2 → 4K[Au(CN)2] + 4KOH 5) Precipitation of Gold :       2K[Au(CN)2] + Zn → K2[Zn(CN)4] + 2Au↓ 6) Purification : Electrolytic Refining      Anode (+)    : Impure Au      Cathode (–) : Pure Au       Electrolyte : AuCl3 + 10 – 12% HCℓ     On passing current pure Au gets deposited at the Cathode.