Question

Which of the following reduction reaction can not be carried out with coke?

Options

• \[\ce{Al2O3 -> Al}\]

• \[\ce{ZnO -> Zn}\]

• \[\ce{Fe2O3 -> Fe}\]

• \[\ce{Cu2O -> Cu}\]

Answer 1

\[\ce{\mathbf{Al_2O_3 \leftarrow Al}}\]

Explanation:

Aluminium oxide (Al₂O₃) is highly stable and cannot be reduced by coke because carbon is not a strong enough reducing agent for it. The line for C/CO lies above Al/Al₂O₃ in the Ellingham diagram, meaning the reduction is not thermodynamically feasible. Hence, Al₂O₃ is reduced electrolytically in the Hall–Heroult process, not by coke.