Baby_GaL - 1-10-2003 at 08:30
Hi
first of all i wonna say that anything to do with science is not my strongest thing
i dont know why....!!!!
but i just want some help with my homework...
1. Why aluminium cannot be extracted from aluminium oxide by heating with carbon.
2. How aluminium can be extracted from aluminium oxide.
I know for some of you this may be easy and you might think hell im dumb but science like i said before is not my strongest subject and i would
appreciate if you could help me.
andrea - 1-10-2003 at 11:35
Out of curiosity only: are you italian?
Google! Do you speak it?
PinkFire - 1-10-2003 at 12:12
How detailed of an answer are you looking for? #1 could simply be answered "Aluminum is a highly active metal so it will not react with carbon to
reduce the oxide." #2, via some sort of electrolysis. But I could be wrong.
DDTea - 1-10-2003 at 15:33
The Oxide could be separated from the Aluminum via single-replacement reaction by a more active metal (If Aluminum Oxide is soluble in water, check
that).
Such a metal could be Magnesium, Calcium, Beryllium, or any of the Alkalis (Sodium, Potassium, etc.)
The Ed - 1-10-2003 at 20:08
aluminum cant be replaced with carbon because aluminum is more electropositive.
In the old days the way they isolated aluminum by reacting metallic sodium with aluminum trifluoride or trichloride. this process was very tedious,
and as a result aluminum was more valuable than gold
now the much easier process is electrolysis. The way this is done is hot aluminum oxide in carbon-lined steel acting as the cathode with carbon
anodes.
JustMe - 2-10-2003 at 13:15
The Aluminum Oxide must first be dissolved in molten Cryolite... Na3AlF6, which is now produced artificially instead of mined.
BASF - 3-10-2003 at 02:44
Another way of answering this question:
1)Aluminum reacts with carbon to give aluminum carbide.
2)Out of bauxit: (mainly Al2O3)
1st step is purification: bauxit is dissolved in sodium hydroxide, then precipitated by lowering the concentration of OH- >Al(OH)3.
This is then calcinated(heated at white glow) to give Al2O3.
Because of the high melting point of Al2O3(remember that it is used in the tiles of the Space Shuttle for re-entry), it is mixed with Cryolite(as
mentioned in the above posting).
This lowers the melting point very considerably(if interested: it is the "eutectic-mixture-effect"
and process is much more economical.
In the molten state, Al2O3 splits into Al3+ and O2- -Ions.
Thus it is possible to seperate the aluminum by electrolysis.
Aluminum is lighter than the molten Al2O3/cryolite-mix.
It floats onto the surface and is run off.
Hope this was helpful.
[Edited on 3-10-2003 by BASF]