Ores

• Where does gold occur in the Earth's crust?

  Gold occurs uncombined in the Earth's crust.
• What are the two reactions needed to produce copper from copper oxide?

  1. Heating copper carbonate to produce copper oxide.
  2. Heating copper oxide with carbon to produce copper.
• Why can copper be produced by heating copper oxide with carbon?

  Because carbon is more reactive than copper and displaces it.
• List the metals in order of increasing reactivity from potassium to gold.

  • Potassium
  • Sodium
  • Calcium
  • Magnesium
  • Aluminium
  • Carbon
  • Zinc
  • Iron
  • Copper
  • Silver
  • Gold
• Why are very unreactive metals like gold and platinum found in their native state?

  Because they have not reacted with other elements to form compounds.
• What is an ore?

  An ore is a rock that contains enough of a compound to extract a metal for profit.
• What is haematite an ore of?

  Haematite is an ore containing iron oxide.
• How is iron extracted from iron oxide?

  By heating the iron oxide with carbon.
• Why does carbon displace iron in the extraction process?

  Because carbon is more reactive than iron.
• What is the balanced equation for the reaction of iron oxide with carbon?

  iron oxide + carbon → iron + carbon dioxide
• What method is used for extracting metals below carbon in the reactivity series?

  • Heating the ore with carbon.
  • Example: Iron is extracted from iron oxide.
• What is the method used to extract metals higher than carbon?

  Electrolysis of molten ionic compounds.
• What is produced by the electrolysis of aluminium oxide?

  Aluminium and oxygen.
• Why is electrolysis considered expensive?

  Because a lot of energy is needed to keep metal oxides molten.
• Name two metals that can only be extracted from their ores by electrolysis.

  Aluminium and sodium.
• What is the balanced equation for the extraction of zinc from zinc oxide?

  ZnO + C → Zn + CO₂
• Why is electrolysis not used for large-scale extraction of zinc?

  Because it is not cost-effective compared to heating with carbon.
• What are the biological methods of metal extraction?

  • Bioleaching: Uses bacteria to extract metals from low-grade ores.
  • Phytoextraction: Uses plants to absorb metal compounds.
• What is produced during the traditional extraction of copper from copper sulfide?

  Copper and sulfur dioxide.
• What is leachate in the context of bioleaching?

  It is a solution containing copper ions produced by bacteria.
• How is copper extracted from leachate?

  By displacement using scrap iron, then purified by electrolysis.
• What are the advantages and disadvantages of bioleaching and phytoextraction?

  Advantages:

  • No harmful gases produced.
  • Less landscape damage.
  • Conserves higher-grade ores.

  
  

  Disadvantages:

  • Very slow process.
  • Toxic substances can be produced.
  • Dependent on weather conditions.
• Why are bioleaching and phytoextraction considered slow methods?

  Because they rely on biological processes that take time.
• What is the ionic equation for the displacement reaction between copper ions and iron?

  Cu²⁺(aq) + Fe(s) → Cu(s) + Fe²⁺(aq)
• How can sodium be extracted from sodium chloride?

  By electrolysis of molten sodium chloride.
• Why was aluminium more expensive than gold when first extracted?

  Because the extraction process was very costly and complex.
• Why is iron extracted from iron oxide using a different method than aluminium from aluminium oxide?

  Because iron is less reactive than aluminium and can be extracted with carbon.
• Compare and contrast biological and non-biological methods of metal extraction.

  Biological methods:

  • Use living organisms.
  • Generally slower.
  • Less environmental impact.

  
  

  Non-biological methods:

  • Use chemical processes.
  • Generally faster.
  • Higher environmental impact.