can you describe the extraction of aluminum by the Hall's Process.

Asked by haritsourabhharit | 3rd Oct, 2010, 11:40: AM

Expert Answer:

The Hall-Heroult process involves electrolysis of a molten mixture of aluminium oxide (Al2O3) and cryolite (Na3AlF6) at about 1000oC in a cell with graphite electrodes.

           Electrolysis of pure Al2O3 is impractical because it melts at very high temperature (2045oC) and electrolysis of aqueous Al3+3+ ion. Thus use of cryolite as a solvent for Al2O3 is the key to the success of Hall – Heroult process. solution is not feasible because water is reduced in preference to Al

             The electrode reactions are still not fully understood, but they probably involve complex anions of the type AlFxOy+3-x-2y formed by the reaction of Al2O3 with Na3AlF6. The complex anions are reduced at the cathode to molten Al metal and are oxidized at anode to O2 from O22- gas which reacts with graphite anodes to give CO2 gas. As a result the anodes are chewed up rapidly and must be replaced frequently

 
Cathode: Al3+ +3e -> Al
Anode: O2- -2e->O
O+O ->O2
C + O2->CO2

Answered by  | 3rd Oct, 2010, 04:12: PM

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