Chemistry (1 Viewer)

[Ath]

Can ne1 please help me about the chem assignment

about the "research extraction process of aluminium in australian setting"

refer to:

1. economic/ non-economic deposits of matural resources

2. describe relationship betwwen commercial prices of common metals and their actual abundances and relative costs of production

3.explain why ores are non renewable resources

4. describe separation processes, chemical reactions, energy considerations involved with extractin aluminium from its ores

5. recount steps to recycle aluminiium

KEY !! 6. present extraction process in Flowchart

thx i wud really appreciate help or even sites

Thx guys !

 

[zahid]

Seperation process stuff

Aluminium
Aluminium is the most abundant metal in the Earth's crust. Most aluminium ores do not have a high enough aluminium content to make extraction economical. Bauxite, its main ore, is the one from which aluminium is extracted.

Bauxite is impure aluminium oxide (Al2O3). The first step is to purify it. Aluminium is more reactive than carbon so it cannot be reduced by carbon. Instead, aluminium oxide is electrolysed (see Chapter 11: Uses of Electrolysis). There are, however, a few considerations to take into account for the electrolysis of aluminium oxide:

For electrolysis, as you should know, the ions must be free to move. They are only free when molten or in solution. Aluminium oxide does not dissolve in water and its melting point is over 2000C. The energy required to heat it would make the process inefficient. So, aluminium oxide is dissolved in cryolite (Na3AlF6), another ore of aluminium. Cryolite melts at a lower temperature, so the electrolysis can occur at a lower temperature (about 1000C).
Graphite electrodes are used. Molten aluminium is produced at the cathode and sinks to the bottom of the cell, from where it is piped off.

Al3+ (l) + 3e- Al(l)
Oxygen is produced at the anode. This means that the graphite electrodes are oxidised to carbon dioxide, so they waste away and must be replaced regularly.

2O2- (l) O2(g) + 4e-
Electrolysis for the extraction of aluminium consumes large amounts of electricity.
Extraction of aluminium by electrolysis

Aluminium is an extremely useful metal. It is a good conductor, is malleable, ductile and has a very low density. Although reactive, it resists corrosion because of the thin oxide layer on its surface, which prevents oxygen from getting to it. Because of its properties, aluminium has many uses.

Uses of aluminium

Use
Reasons

Kitchen foil
Resists corrosion, malleable

Window frames
Resists corrosion

Aeroplanes
Resists corrosion, low density

Car engines
Resists corrosion, low density

Power cables
Resists corrosion, low density, good conductor

 

[zahid]

The higher up the reactivity series the metals are the more reactive they are and therefore they are harder to be extracted from the earths crust. For example Aluminium which is the most abundant metallic element in the Earths crust.

Aluminium is very difficult to react because it holds on tightly to the element(s) it has combined with and is extracted from its ore by electrolysis. This is a process of splitting up substances by passing an electric current through them. The substance, which decomposes, is called the electrolyte. During this process the metal is produced at the cathode, the negative electrode which attracts the cations, while the non-metal is produced at the anode, the positive electrode which attract the anions. In order to extract aluminium from its ore involves the electrolysis of aluminum oxide. This process involves Bauxite, an impure form of aluminium, which is treated with sodium hydroxide to remove the impurities. Then the aluminium oxide is dissolved in molten cryolite to reduce the temperature and the molten mixture is then electrolysed in a cell. This process however is very expensive and in order to keep the cost low regions were this process is used, hydroelectric power is used to generate electricity.

 

[zahid]

here is something for the economic and non-econopic part

http://www.doir.wa.gov.au/documents/investment/OpprtunitiesAlumin.pdf

 

[ZeGoat]

I had an assignment along these lines before... try theses sites for info...
http://www.rocksandminerals.com/aluminum/aluminum.htm
http://www.science.uwaterloo.ca/~cchieh/cact/applychem/alumina.html
http://www.world-aluminium.org/ (This site is pretty good with heaps of info)
http://www.aluminium.org/
hope they are useful...

 

[zahid]

true those sites are great..

 

[AGB]

ill copy this one to the chem forum as well.... there is some really good stuff here