Eduprobe
Question:
In the metallurgy of aluminium:
Al³⁺ is oxidised to Al(s)
graphite anode is oxidised to carbon monoxide and carbon dioxide
the oxidation state of oxygen changes in the reaction at anode
the oxidation state of oxygen changes in the overall reaction involved in the process
Al³⁺is oxidised to Al(s)
graphite anode is oxidised to carbon monoxide and carbon dioxide
the oxidation state of oxygen changes in the reaction at anode
the oxidation state of oxygen changes in the overall reaction involved in the process
Solution:
The oxidation state of O does not change in either the reaction occurring at the anode or the overall reaction as shown below:
At anode: C + O²⁻ → CO + 2e⁻
CO + O²⁻ → CO₂ + 2e⁻
C + 2O²⁻ → CO₂ + 4e⁻
At cathode: Al³⁺ + 3e⁻ → Al
Overall reaction: 2Al₂O₃ + 3C → 4Al + 3CO₂
Hence, option B is correct.