A) reducing \[A{{l}_{2}}{{O}_{3}}\] with coke
B) electrolysing \[A{{l}_{2}}{{O}_{3}}\]dissolved in \[N{{a}_{3}}Al{{F}_{6}}\]
C) reducing \[A{{l}_{2}}{{O}_{3}}\]with chromium
D) heating alumina with cryolite
Correct Answer: B
Solution :
Aluminium is obtained by electrolyzing alumina dissolved in cryolite \[(N{{a}_{3}}Al{{F}_{6}})\] \[4N{{a}_{3}}Al{{F}_{6}}\rightleftharpoons 12N{{a}^{+}}+4A{{l}^{3+}}+12{{F}^{-}}\] \[4A{{l}^{3+}}+12{{e}^{-}}\to 4Al\](at cathode) \[12{{F}^{-}}\to 6{{F}_{2}}+12{{e}^{-}}\](at cathode) \[2A{{l}_{2}}{{O}_{3}}+6{{F}_{2}}\to Al{{F}_{3}}+3{{O}_{2}}\]
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