C6.1.8-6.1.12 Flashcards
(47 cards)
As an ore what does aluminium exist as?
Bauxite - Aluminium oxide
What process is used to extract aluminium and why?
- Electrolysis as it is more reactive than carbon.
What is the electrolyte in the extraction of aluminium and why?
- A mixture of bauxite and cryolite.
Bauxite is dissolved in cryolite as aluminium oxide has a very high melting point so it would be expensive (2000 degrees C +) - Cryolite allows electrolysis to occur at 950 degrees C
What are the components of the electrolysis cell made of in aluminium extraction?
- Steel outer insulation layer
- Carbon anode and cathode
What is produced at the cathode?
The cations will be sodium and aluminium, since aluminium is less reactive than sodium it will form molten aluminium at the cathode.
What is the half equation for the reaction at the cathode?
Al(3+) + 3e- > Al
What is produced at the anode?
Oxygen is produced and reacts with the graphite anodes making CO2(g)
What is the half equation at the anode?
2O2- > O2 + 4e-
What is a low grade ore?
An ore that only contains small amounts of the desired metal.
State 2 biological extraction methods.
Bioleaching
Phytoextraction
What is acid mine damage?
- Mines flood when abandoned
- Metal sulfides oxidise underwater > sulfuric acid
- H2SO4 reacts with other metal ores.
- Soluble metal compounds form and leave the water as the mine drains
Explain the process of bioleaching.
- Bacteria oxidise iron(||) and sulfide ions and use the energy within the bonds and H2SO4 forms in the presence of H2O and O2.
- Sulfuric acid breaks down copper sulfide ores and other minerals releasing copper (||) ions and other metal ions.
Explain the process of phytoextraction.
- Crops are grown on soils which are low grade ores.
- Complexing agent is added to enhance the metal ion uptake of the plant.
- The crops take up the ions in the soil
- Plant materials are harvested and burnt to produce an ore which will be a high grade ore and the metal is extracted as per usual and is treated as a normal ore.
What are the advantages of bioleaching?
- Cheaper than traditional mining and processing.
- Bacteria occur naturally and don;t need special treatment.
- No GHG produced although little toxic substances are produced.
What are the disadvantages of bioleaching?
- Very slow
- Some toxic substances produced.
- Toxic substances and sulfuric acid may escape int water supplies and soil.
What is a carbon-neutral process?
A net result of no carbon dioxide being released into the atmosphere.
What are the advantages of phytoextraction?
Very close to being a carbon neutral process.
Cheaper than traditional mining processes.
Produces less waste and requires less energy transfer.
What are the disadvantages of phytoextraction?
Very slow as crops take several years before the available metal is removed from the soil.
What is an alloy?
A mixture of two or more elements, one of which is a metal.
What are the main metals that are in the alloy steel?
<1% carbon, iron etc.
What are the properties of steel?
- Harder and stronger than iron.
- Iron on its own corrodes fast but steel doesn’t.
What are typical uses of steel?
Girders, bridge, cars, drill bits etc.
What is solder made of?
- Usually lead and tin or tin and copper.
Explain the melting point of solder.
It has no specific melting point as it is impure, but gradually solidifies as it cools down.
