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Bauxite from Africa is transported to Aughinish in Co - Leaving Cert Chemistry - Question A - 2012
Question A
Bauxite from Africa is transported to Aughinish in Co. Limerick, where it is converted to pure alumina (Al₂O₃). The alumina is then shipped to Russia where aluminium... show full transcript
Worked Solution & Example Answer:Bauxite from Africa is transported to Aughinish in Co - Leaving Cert Chemistry - Question A - 2012
Step 1
Describe the chemical processes used to produce pure alumina from bauxite.
Answer
The production of pure alumina from bauxite involves several key chemical processes:
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Digestion: Bauxite is heated with sodium hydroxide (NaOH) at high temperatures. This process dissolves the bauxite, forming a soluble sodium aluminate solution:
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Seeding: Crystals of aluminium oxide trihydrate (Al₂O₃·3H₂O) are introduced into the sodium aluminate solution to initiate precipitation.
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Precipitation: Aluminium oxide trihydrate precipitates out of the solution as the temperature is lowered, leading to the formation of solid Al₂O₃·3H₂O.
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Conversion: The sodium aluminate solid undergoes conversion via heating, eliminating water, to produce the final pure alumina (Al₂O₃):
These steps lead to the extraction of pure alumina from bauxite.
Step 2
Draw a labelled diagram of the electrolytic cell used to produce aluminium metal from alumina.
Answer
The electrolytic cell used for producing aluminium metal from alumina consists of several key components:
- Graphite Anodes: These are the positive electrodes that facilitate the oxidation reaction.
- Graphite Cathode: This is the negative electrode where reduction occurs.
- Molten Aluminium: The product aluminium collects at the bottom of the cell.
- Cryolite: The electrolyte that lowers the melting point of alumina.
The labelled diagram would typically show the arrangement of these components within the cell, indicating the flow of electricity and the reactions taking place at each electrode.
Step 3
Explain why the recycling of aluminium is environmentally desirable.
Answer
The recycling of aluminium is environmentally beneficial for several reasons:
- Energy Conservation: Recycling aluminium saves approximately 95% of the energy required to produce new aluminium from ore, significantly reducing overall energy consumption.
- Less Waste: It greatly reduces the volume of waste materials sent to landfills, addressing waste management issues.
- Resource Preservation: By recycling, we conserve natural resources and reduce the demand for raw bauxite extraction, which can be environmentally invasive.
- Lower Environmental Impact: Overall, the recycling process has a much lower carbon footprint compared to primary aluminium production, helping to mitigate climate change.