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Q.
The mass of carbon anode consumed (giving only carbondioxide) in the production of $270\, kg$ of aluminium metal from bauxite by the Hall process is
(Atomic mass $Al =27$ )
JIPMERJIPMER 2007General Principles and Processes of Isolation of Elements
Solution:
In Hall and Heroult process
$ 2 Al _{2} O _{3} \longrightarrow 4 Al +3 O _{2} $
$ 4 C +3 O _{2} \longrightarrow 2 CO _{2}+2 CO \uparrow $
$ 2 Al _{2} O _{3}+4 C \longrightarrow 4 Al +2 CO _{2}+2 CO $
Only for removal of $CO _{2}$, following equation is possible
$\because$ For $108\, g$ of $Al , 36\, g$ of $C$ is required in above reaction
$\therefore $ For $270\, g$ of $Al$ require amount of $C$
$=\frac{36}{108} \times 270=90\, g$
