Extraction of Metals - Result Question 15
####15. Hall-Heroult’s process is given by
(2019 Main, 10 Jan I)
(a) $ZnO+C \xrightarrow{\text { Coke, } 1673 K} Zn+CO$
(b) $Cr _2 O _3+2 Al \longrightarrow Al _2 O _3+2 Cr$
(c) $2 Al _2 O _3+3 C \longrightarrow 4 Al+3 CO _2$
(d) $Cu^{2+}(a q)+H _2(g) \longrightarrow Cu(s)+2 H^{+}(a q)$
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Solution:
- Hall-Heroult’s process is an electro-reduction process by which pure alumina $\left(Al _2 O _3\right)$ is reduced to crude $Al$.
In this process, electrolysis of a fused mixture of $Al _2 O _3$, $Na _3\left[AlF _6\right]$ (cryolite) and $CaF _2$ (fluorspar) is carried out at carbon cathode and graphite anode.
The overall reaction is represented as:
$$ 2 Al _2 O _3+3 C \longrightarrow 4 Al+3 CO _2 $$
