Question

explain electrolytic refining of aluminium into aluminium metal with diagram ​

Answer 1

Answer:

The electrolysis of alumina is carried out in a steel tank lined inside with graphite. The graphite lining serves as  

    cathode. Anode is also made of graphite rods hanging in the molten mass.

   The electrolyte consists of alumina dissolved in fused Cryolite(Na3AlF6) and Fluorspar(CaF2).

   Cryolite lowers the melting point of alumina to 9500C and fluorspar increases the fluidity of the mass so that  

   the liberated aluminum metal may sink at the bottom of the cell.

   When electric current is passed through this mixture, the aluminum is collected at the cathode in molten state

   and sinks at the bottom and is tapped off.

                     

                      Ionization of Alumina:

                                                           2Al2O3 → 6O-2 + 4Al+3

                      Reaction at  Cathode:

                                                          4Al+3 + 12e- → 4Al

                      Reaction at Anode:

                                                        6O-2 → 3O2 + 12e-

                                                          C + O2 → CO2

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REFINING OF ALUMINIUM

 

   

   Aluminum metal produced by the electrolysis of alumina is 99% pure but contains impurities of Fe, Si  and Al2O3. Aluminum is  

   further refined by hoope’s method.

HOOPE’S METHOD

 

   

  This is an electrolytic process. Electrolytic cell is made of iron, which is lined with carbon at the bottom. It contains three layers of

   fused mass. The lower layer consists of an alloy of impure aluminum with copper. This layer serves as anode. The middle layer  

   consists of a solution of cryolite (Na3AlF6) and barium fluoride. The upper layer consists of pure aluminum and serves as  

   cathode. These three layers are separated from each other due to difference in specific gravity.

   During electrolysis Al+3 ions from the middle layer migrate to the upper layer where they are reduced to aluminum by gaining  

   three electrons. Equal numbers of Al+3 ions are produced in the lower layer. These ions migrate to the middle layer. Pure  

  aluminum is tapped off from time to time. Hoope’s method gives 99.99% pure aluminum.  

   

                                 

Answer 2

Explanation:

during electrolysis positively charged aluminium ions gain electron from the cathode and form molten aluminium.oxide ions lose electron at the anode and form oxygen molecules