Lecture Notes: Early Metal Discovery and Reduction Processes

Discovery of Early Metals

• Key metals: Gold, Silver, and Copper
• Occurrence: Sometimes found as pure metals in Earth's crust
  • Examples include tiny pieces of pure gold and veins of copper
• Rarity of pure state: Finding metals in pure form is rare

Copper

• Common Forms: Typically found combined with Iron, Sulfur, and Oxygen
  • Example: Copper Oxide (CuO)

Extraction of Pure Copper (Reduction)

• Reduction Process: Removal of oxygen to obtain pure metal
• Methods:

  • Hydrogen as a Reducing Agent:

    • Hydrogen gas is passed over Copper Oxide
    • Safety: Mixture of hydrogen and air is explosive; excess hydrogen burned cleanly
    • Reaction:
      • Hydrogen + Copper Oxide → Copper + Water
      • CuO (s) + H₂ (g) → Cu (s) + H₂O (g)
    • Hydrogen is oxidized, Copper Oxide is reduced
    • Reaction reverses once hydrogen and heat are removed

  • Carbon as a Reducing Agent:

    • Carbon mixed with Copper Oxide and heated
    • Reaction:
      • Carbon + Copper Oxide → Copper + Carbon Dioxide
      • CuO (s) + C (s) → Cu (s) + CO₂ (g)
    • Carbon is oxidized, Copper Oxide is reduced

Reduction of Other Metal Oxides

• Lead Oxide and Carbon: When heated, forms beads of pure molten lead
  • PbO (s) + C (s) → Pb (l) + CO₂ (g)
• Iron Oxide and Carbon: No reaction observed

Key Questions

• Reactivity: Why does carbon reduce copper and lead oxides but not iron oxide?