MetallurgyHard
Question
Which of the following reduction reactions are actually employed in commercial extraction of metals?
Options
A.Fe2O3 + 2Al → Al2O3 + 2Fe
B.Cr2O3 + 2Al → Al2O3 + 2Cr
C.2Na[Au(CN)2] + Zn → Na2[Zn(CN)4] + 2Au
D.Cu2S + 2CuO → 6Cu + SO2
Solution
(A) 2Al + Fe2O3 → AI2O3 + 2Fe (molten) ; DH = - 3230 kJ (The reaction is used for thermite welding)
(B) Aluminonthermic process : Cr2O3 + AI → 2Cr (molten) + AI2O3
(C) Extraction of gold : 4Au (s) + 8 CN- (aq) + O2 (g) + 2H2O (l)→ 4 [Au(CN)2]- (aq) + 4OH- (aq)
2[Au(CN)2]- (aq) + Zn (s) → [Zn(CN)4]2- (aq) + 2 Au (s)
(D) Self-reduction method : Cu2S + 3O2 → 3Cu2O + 2 SO2 ; 2Cu2O + Cu2S → 6Cu + SO2
(B) Aluminonthermic process : Cr2O3 + AI → 2Cr (molten) + AI2O3
(C) Extraction of gold : 4Au (s) + 8 CN- (aq) + O2 (g) + 2H2O (l)→ 4 [Au(CN)2]- (aq) + 4OH- (aq)
2[Au(CN)2]- (aq) + Zn (s) → [Zn(CN)4]2- (aq) + 2 Au (s)
(D) Self-reduction method : Cu2S + 3O2 → 3Cu2O + 2 SO2 ; 2Cu2O + Cu2S → 6Cu + SO2
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