JEE Advance - Chemistry (2013 - Paper 2 Offline - No. 1)
Explanation
Extraction of various metals from their respective concentrated ores is carried out by different methods:
(i) Carbon Reduction of Hematite:
The process for the extraction of iron from hematite (Fe2O3) involves carbon reduction:
| 3 Fe2O3 + CO → 2 Fe3O4 + CO2(g) |
| Fe3O4 + 4 CO → 3 Fe(s) + 4 CO(g) |
This reaction occurs at temperatures between 500-800 K.
| FeO(s) + CO(g) → Fe(s) + CO2(g) |
Carbon monoxide needed for the reduction is produced as follows:
| C(s) + CO2(g) → 2 CO |
The net reaction can be written as:
| FeO(s) + C(s) → Fe(s) + CO(g) |
Thus, carbon and its oxides are utilized for the reduction of iron ores such as Fe2O3.
(ii) Carbon Reduction of Cassiterite (SnO2):
The reduction process involves carbon:
| SnO2(s) + C(s) → Sn(s) + CO2(g) |
Therefore, carbon is used for the reduction of cassiterite ore.
(iii) Electrolytic Refining of Aluminium (Al2O3):
Aluminium is extracted from bauxite using electrolysis. The reduction occurs at the cathode:
| Al3+ + 3 e- → Al(s) |
The reduction of Al3+ takes place at the cathode.
(iv) Dow's Process for Extraction of Magnesium from Dolomite (MgCO3.CaCO3):
Dolomite is treated with hydrochloric acid (HCl) to produce magnesium chloride (MgCl2). Electrolysis of MgCl2 reduces Mg2+ to magnesium metal at the cathode:
| Mg2+(aq) + 2 e- → Mg |
Magnesium metal is obtained by the reduction of Mg2+.
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