Extraction of Aluminium

What is an aluminum ore called?

bauxite

What happens when we purify bauxite?

becomes a white powder - aluminium oxide from which aluminium can be extracted.

The extraction is done by electrolysis, but first the aluminium oxide must be 1.______ so that electricity can pass through it.

2. Why is obtaining aluminium by elctrolysis very expensive/ why is aluminium expensive even though it is the most abundant metal on Earth?

1. melted

2. it has a very high melting point (over 2,000 degrees Celsius) so it would be very expensive to melt it as it requires a lot of energy.

what is molten cryolite and why is it used.

• It is an aluminium compound with a lower melting point than aluminium oxide.

• The use of molten cryolite as a solvent reduces some of the energy costs involved in extracting aluminium by allowing the ions in aluminium oxide to move freely at a lower temperature.

Here are one of the forms of electrolysis.

Aluminium ions receive electrons at the negative electrode and are reduced to aluminium atoms:

What is the half equation of the aluminium?

what type of reaction is this?

Al³⁺ + 3e^– → Al (reduction – gain electrons)

Oxide ions lose electrons at the positive electrodes and are oxidised to oxygen gas:

What is the half equation for this?

What type of reaction?

2O^2– → O₂ + 4e^– (oxidation – lose electrons)

Why does oxygen being given off increase the cost f the process?

This oxygen reacts with the carbon of the positive electrodes, forming carbon dioxide, so they gradually burn away. As a result, the positive electrodes have to be replaced frequently. This adds to the cost of the process.

There are a number of important factors to consider when choosing the site of an aluminium extraction plant. It should be:

At least 3/5

• in close proximity to a power station, in order to provide the large supply of electricity needed for the electrolysis

• near the coast to allow for the import of raw materials

• near roads and railway lines to allow for the product to be taken to where it is needed

• near a town or city, so that workers have somewhere to live close by

• away from built-up areas, so that the noise and pollution of the site do not affect the local population