O-Level Chemistry: Extraction of Metals

1. Extraction of Iron (Fe)

Physical Properties and Occurrence

• Iron is highly magnetic, malleable, and ductile.
• Pure iron is soft but hardens in alloys (e.g., steel).
• It corrodes easily in air and moisture.

Iron ores include Haematite (Fe2O3), Magnetite (Fe3O4), and Iron(III) Carbonate (FeCO3).

Extraction Process (Blast Furnace)

1. Heating and Reducing Agent Generation: Coke burns to produce CO as reducing agent.
   C(s) + O2(g) → CO2(g)
   CO2(g) + C(s) → 2CO(g)
2. Reduction of Iron Oxide: Fe2O3 reacts with CO to give molten iron.
   Fe2O3(s) + 3CO(g) → 2Fe(l) + 3CO2(g)
3. Slag Formation: Limestone reacts with SiO2 impurities to form slag.
   CaCO3(s) → CaO(s) + CO2(g)
   CaO(s) + SiO2(s) → CaSiO3(l)

Uses of Iron

• Cast iron, steel, construction, machinery, and road making.

2. Extraction of Aluminium (Al)

Physical Properties and Occurrence

• Light metal, good conductor of heat and electricity, ductile, malleable, resistant to corrosion.

Aluminium is extracted from Bauxite (Al2O3·2H2O).

Extraction Process (Hall-Héroult Process)

1. Purification of Bauxite: Dissolve in NaOH to form Sodium Aluminate.
   Al2O3 + 2NaOH + 3H2O → 2NaAl(OH)4
2. Electrolysis: Alumina dissolved in molten cryolite.
   Al3+ + 3e− → Al(l) (Cathode)
   2O2− → O2 + 4e− (Anode)
   C + O2 → CO2

Uses of Aluminium

• Cooking utensils, overhead cables, roofing sheets, paints, alloys.

3. Extraction of Copper (Cu)

Physical Properties and Occurrence

• Ductile, malleable, excellent conductor, resistant to corrosion.
• Occurs as free metal but mainly in sulphide ores like Copper Pyrite (CuFeS2).

Extraction Process (Thermal Reduction)

1. Roasting and Smelting: Ore partially burnt in air to form Cu2S and FeO. Silica added to remove FeO as slag.
2. Auto-Reduction: Cu2O + Cu2S → 6Cu + SO2
3. Purification: Electrolytic refining using CuSO4 solution.
   • Anode: impure copper, Cathode: pure copper.
   • Copper dissolves from anode and deposits on cathode.

Uses of Copper

• Electrical wiring, plumbing, brass & bronze alloys.

4. Extraction of Titanium (Ti)

Physical Properties and Occurrence

• Hard metal, high melting point, corrosion resistant.
• Occurs in Rutile (TiO2) in Akonolinga, Cameroon, and Ilmenite (FeTiO3).

Extraction Process (Kroll Process)

1. Preparation of TiCl4: Ore + C + Cl2 → TiCl4 + CO2
   TiO2 + C + 2Cl2 → TiCl4 + CO2
   2FeTiO3 + 3C + 7Cl2 → 2TiCl4 + 2FeCl3 + 3CO2
2. Purification: Fractional distillation of TiCl4.
3. Reduction: TiCl4 reduced by Na or Mg.
   TiCl4 + 4Na → Ti + 4NaCl
   TiCl4 + 2Mg → Ti + 2MgCl2

Uses of Titanium

• Construction (chemical plants), aerospace (aircraft & space vehicles), energy (nuclear reactors).