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Solutions and Electrochemistry VII (Hall-Heroult Process (Extraction of…
Solutions and Electrochemistry VII
Electrolytic Cells
Both electrolytes touching same solution
Non-standard conditons
Different IUPAC labelling convention
Same as galvanic cells except SIGNS SWITCHED
NaCL Electrolysis
Down's Cell
Na+ + e- ---> Na
2Cl- ----> Cl2 +2e-
Faraday's Laws
First Law
The number of moles of a species formed at an electrode during electrolysis is proportional to the electrochemical charge passed
Second Law
A given charge liberates different species in the ratio of their relative formula masses divided by the number of electrons in the electrode reaction
Q = It; Q/F = n (e-); Stoichiometry
Hall-Heroult Process
Extraction of aluminium
Al2O3 dissolved in cryolite (Na3AlF6)
800-1000 degrees C
Al3+ + 3e- ---> Al
C + 2O2- ---> CO2 + 4e-
Other applications
Electroplating
Anode/cathode same material
Purification of copper
Pure copper cathode
Impure copper anode
Leaves impurities as sludge