c6.1

• ores

  Metal ore: a rock that contains enough metal work that it worth extracting

  → iron oxide - haematite

  → aluminium oxide - bauxite

  • unreactive metals do not have to be extracted chemically because they are usually found as the uncombined element. 

  → e.g. gold and platinum, from the Earth’s crust, these are known as native metals
• extraction of metals.

  Metals placed ABOVE carbon are extracted using electrolysis.

  Metals placed BELOW carbon are extracted using heat and a reducing agent [e.g. carbon/carbon monoxide] in a blast furnace. 

  A) electrolysis

  B) expensive

  C) carbon

  D) blast furnace

  
• extraction of copper

  • Stage 1: The copper sulfide is heated in the air to produce the oxide 
  • 2CuS (s) + 3O2 (g)    →   2CuO (s) + 2SO2 (g)
  • Stage 2: The copper oxide is reduced by carbon

  2CuO (s) + C (s)  →   2Cu (s) + CO2 (g)
• What is the primary ore used for iron extraction in a blast furnace?

  Haematite
• What are the raw materials added to the blast furnace for iron extraction?

  Haematite, coke, and limestone
• What happens when hot air is blown into the bottom of the blast furnace?

  Coke burns, forming carbon dioxide
• What is the chemical reaction when coke burns in hot air?

  C + O2 → CO2
• What occurs in Zone 2 of the blast furnace?

  Coke reacts with carbon dioxide to form carbon monoxide
• What is the chemical equation for the reaction of carbon dioxide with coke in Zone 2?

  CO2 (g) + C (s) → 2CO (g)
• How does carbon monoxide contribute to iron extraction in Zone 3?

  It reduces iron (III) oxide to form iron
• What is the chemical reaction for the reduction of iron (III) oxide in the blast furnace?

  Fe2O3 (s) + 3CO (g) → 2Fe (l) + 3CO2 (g)
• What state is iron in after it is extracted from the blast furnace?

  Liquid
• Where does the molten iron collect in the blast furnace?

  At the bottom of the furnace
• What happens to the molten iron after it collects at the bottom of the furnace?

  It is tapped off
• What is the role of limestone in the blast furnace?

  It helps remove impurities
• How do the reactions in the blast furnace contribute to the extraction of iron?

  They convert iron oxide to molten iron
• What is the chemical formula for limestone?

  CaCO3
• What happens to calcium carbonate in the furnace?

  It decomposes to form calcium oxide and carbon dioxide
• What is the reaction equation for the decomposition of calcium carbonate?

  CaCO3 (s) → CaO (s) + CO2 (g)
• What does calcium oxide react with in the iron ore process?

  It reacts with silicon dioxide
• What is formed when calcium oxide reacts with silicon dioxide?

  Calcium silicate
• What happens to calcium silicate during the iron extraction process?

  It melts and collects as molten slag
• What is bioleaching?

  A technique using bacteria to extract metals
• What do some strains of bacteria do in bioleaching?

  They break down ores to form acidic solutions
• What is the solution called that contains metal ions from bioleaching?

  Leachate
• How can metal ions in leachate be extracted?

  By displacement reactions or electrolysis
• What types of ores is bioleaching often used for?

  Sulfides like CuS or Fe2S
• What is a disadvantage of bioleaching?

  It produces toxic substances needing treatment
• Besides primary extraction, where else is bioleaching used?

  In mining waste clean-up operations
• What is a limitation of extracting some metals with carbon?

  Some metals are too reactive
• How is aluminium extracted from aluminium oxide?

  Using electrolysis
• What is the first step in extracting aluminium from bauxite?

  Purify bauxite to produce aluminium oxide
• Why is aluminium oxide dissolved in molten cryolite?

  To lower its melting point for efficiency
• What is produced at the cathode during aluminium extraction?

  Aluminium
• What is produced at the anode during the electrolysis of aluminium oxide?

  Oxygen
• What is a disadvantage of the electrolysis process for aluminium extraction?

  It requires a high amount of electricity
• What happens to the carbon in graphite anodes during electrolysis?

  It reacts with oxygen to produce carbon dioxide
• What is required for the extraction of low-grade ores?

  Other techniques are being developed
• What is a disadvantage of biological extraction methods?

  They are very slow
• What is phytomining?

  A process using plants to absorb metals