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AS/A-level Chemistry - Extraction of Metals

Inorganic Chemistry, Extraction of metals, Reduction

July 7, 2021

Do you remember I/GCSE Chemistry regarding metal extractions? In AS/A-level Chemistry, we will study more in-depth about it!๐Ÿ‘ฉโ€๐Ÿซ

Iron

Reducing Agent and reasons:

  • Coke (a cheap form of carbon from coal) and limestone.
  • Coke is the reducing agent and some iron (III) oxide is reduced by carbon, however most is reduced by carbon monoxide gas โ€“ as it is a gas it can circulate freely in the blast furnace.
Condition:
  • Hot air โ€“ Blast furnace (The furnace is hearted by hot air and the combustion of coke inside the furnace raises the temp further. The furnace is about 1500ยฐC or 2000K).
  • Limestone removes any acidic calcium carbonate.
Reduction equation:
  • When iron oxide is reduced by carbon:
    • 2Fe2O3 (s) + 3C (s) ร  4Fe (l) + 3CO2 (g)
  • When iron oxide is reduced by carbon monoxide:
    • C (s) + O2 (g) โž” CO2 (g)
    • CO2 (g) + C (s) โž” 2CO (g)
    • Fe2O3 (s) + 3C O(s) โž” 2Fe (l) + 3CO2 (g)

โ€‹Social/ Environmental/ Economic Considerations:

  • Reduces scrap iron in landfill as it can be recycled.
  • Extracting more iron produces CO2 so it is better to recycle.
  • CO2, CO and SO2 (acid rain) is released.
  • Slag can be used as an aggregate do can be flooded as a building material.
  • Carbon impurity makes iron a poor building material โ€“ brittle.
  • CO is toxic so it is burnt more to make CO2 (a greenhouse gas).

Copper

Reducing Agent:

  1.  Carbon/ Carbon monoxide
  2.  Scrap iron

Condition:

  1. High temperature to decompose the carbonate, then add the carbon.
  2. Cu2+ with dilute acid spray and add bacteria. 

Reduction Equation:

1. CuCO3 โž” CuO + CO2

CuO + C โž” Cu + CO

2. Cu2+(aq) + Fe (s) ร  Cu (s) + Fe2+(aq)

Social/ Environmental/ Economic Considerations:

1. Metal produced contained carbon impurity

2. Low energy cost

Using waste material- recycling scrap iron rather than adding to landfill.

Scrap iron is available and cheaper to buy than copper is to sell.

Aluminum

Reducing agent and reasons:

  • At the cathode each Al3+ ion gains 3 electrons to form an atom of aluminum. Here aluminum is being reduced.
  • Oxidation happens at the anode in electrolysis. Here the oxide ions O2- have been oxidised to form oxygen gas.
  • Electric current

Conditions:

  • Aluminum is more reactive than carbon so it has to be extracted from its ore by electrolysis.
  • The aluminum oxide is added to the reaction cell filled with molten cryolite (a less common ore). The cryolite lowers the melting point of aluminum oxide to save energy.
Reduction Equation
  • Reduction is gain of electrons REG
  • Al3+ + 3e- โž” Al
  • Loss of electrons is oxidation LEO
  • 2O2- โž” 02 + 4e-

Social/ Environmental/ Economic Considerations:

  • Recycling Al uses only 5% of the energy of extracting, so it is cheaper and better for the environment to recycle.
  • High energy costs.
  • Done in places with hydroelectric Power Stations.
  • Carbon electrodes need to be replaced

Titanium

Reducing agent:

  • Reacted with coke and chlorine at 1137K to produce titanium chloride. 
  • Then this is reacted with sodium or magnesium at 1300K in an argon atmosphere. (Na or Mg)

Condition:

  • An inert argon atmosphere is needed to prevent the metal reacting with nitrogen and oxygen in the air and the TiCl4 reacting with water in air to produce HCl.
  • Chorine, coke and 1137K.
  • Purified by distillation

Reduction equation:

TiO2 + 2C + 2Cl2 โž”TiCl4 + 2Cu

TiCl4 + 4Na โž” Ti + 4NaCl OR TiCl4 + 2Mg โž” MgCl2 + Ti

Social/ Environmental/ Economic Considerations:

  • A batch process as it is done in two steps so it isnโ€™t as efficient and uses more energy.
  • Has to be distilled to purify.
  • More expensive due to re-energy costs.
  • Low density metal.
  • Strong unreactive metal that can with stand high temperatures.

Tungsten

Reducing agent: Hydrogen

Condition: High temperature

Reduction equation: WO3 + 3H2 โž”W +3H2O

Social/ Environmental/ Economic Considerations:

  • Using hydrogen as a reducing agent is the last resort as it is very flammable.
  • Cannot be reduced by carbon as CO2 is formed.
  • Hydrogen is not a renewable source.
  • Tungsten is very strong and useful.

References:

https://secondaryscience4all.wordpress.com/2014/07/21/iron-extraction-blast-furnace/

https://ibchem.com/IB/ibnotes/full/ope_htm/hall_cell.htm

This is the end of the topic!

Drafted by Cherry (Chemistry)

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