Extraction of Aluminium by Electrolysis
Edited by Jamie (ScienceAid Editor), Taylor (ScienceAid Editor), SmartyPants, Sim and 1 other
Please note that this article uses the British English spelling of aluminum, but this is exactly the same as aluminum - this is simply the North American English spelling.
Aluminum has a very high melting point and strong bonding between atoms, so it doesn't readily dissolve in water. Instead, molten cryolite (Na3AIF6) is used.
The pure aluminum is attracted to the cathode, which is a lining of graphite. The oxygen is attracted to the anode, and bubbles through the solution.
At the cathode, reduction takes place as electrons are gained:
Al3+ + 3e- ® Al
At the anode, oxidation takes place as electrons are lost:
2O2- ® O2 + 4e-
At the anode also, the oxygen formed will react with the anode (which is made of carbon) to form carbon dioxide. This means the anodes must be frequently replaced.
This process uses a lot of electricity and is expensive. Therefore, aluminum is much more expensive than other metals that are easier to extract (like iron, but its desirable characteristics mean that it is still widely used.
Aluminum is the most widely used metal after iron. It is mostly used in an alloy with another metal, this means it is mixed with another metal to produce another compound that has a certain desirable characteristic - like stainless steel.
Some common uses of aluminum include making cars, trains, and bicycles. Because it's reasonably strong, but not too heavy, your aluminum bicycle won't break and won't be too difficult to ride. Some packaging like foil and cans are also made from aluminum. This is especially important in recycling since some soft drink cans are made of steel rather than aluminum - but they can be sorted using magnets. Cooking utensils are often made from aluminum because it is very good at conducting heat, and will warm the food evenly.
Questions and Answers
How is aluminum extracted using electrolysis. please, can you help mate ;)?
Help me I really need help for my class work. I really need a lot of help
Aluminum is extracted from aluminum oxide by a process called electrolysis.
- First of all, aluminum oxide needs to be in molten form to extract the aluminum ions. Aluminum oxide, however, has a high melting point. Therefore, aluminum oxide is dissolved in molten cryolite. Cryolite is a form of an aluminum compound that has a lower melting point that aluminum oxide.
- The steel case, used in electrolysis, is coated by graphite. Graphite is a form of carbon and acts at the negative cathode.
- The positive anodes are also made of graphite but are immersed in the molten cryolite solution.
- When electricity flows,
- Aluminum ions, from the aluminum oxide, are formed at the negative cathode and then sink to the bottom because they are heavier than the cryolite solution. Then, the aluminum that has sunk to the bottom is collected in liquid form.
- On the other hand, the oxygen, from the aluminum oxide, forms at the positive anode and reacts with the carbon of the graphite to form carbon dioxide CO2.
To visualize the process of electrolysis please refer to the diagram above.
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Categories : Applied
Recent edits by: Sim, SmartyPants, Taylor (ScienceAid Editor)