1.

Whatistherole ofgraphiteintheelectrometallurgyofaluminium ?

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Solution :Intheelectrometallurgyofaluminum, afusedmixtureofalumina,cryoliteandflourspar (`Ca F_2`) iselectrolysedusinggraphiteas anodeandgraphite linedironas cathode. DURINGELECTROLYSIS, Al isliberatedatthecathodewhileCOand` CO_ 2`are liberatedattheanode.
At cathode:` Al^( 3 +) ("melt" )toAl(l) `
At anode:`C (s)+O ^(2 - )(" melt" )toCO (g)+2 E ^(-) `
` C(s)+2O ^( 2 -) ("melt ") toCO_ 2(g) +4 e ^( - ) `
Ifinsteadofgraphite, somemetalisusedas theanode,then` O_2`liberatedwillnot onlyoxidisethemetalofthe electrodebut wouldalsoconvertsome of theAl libertedatthecathode backto`Al _ 2O_3`.
Sincegraphiteis muchcheaperthan anymetal,therefore , graphiteis usedasthe anode. Thus,the ROLE ofgraphiteinelectrometallurgyofAl istopreventtheliberationof ` O _ 2 `at theanodewhich mayotherwiseoxidisesome oftheliberatedAl backto` Al _2 O _3`.


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