Question

\Which of the following reduction reaction cannot be carried out with coke?

• A. ${\mathrm{Fe}}_2{\mathrm{O}}_3\to \mathrm{Fe}$
• B. $\mathrm{ZnO}\to \mathrm{Zn}$
• C. ${\mathrm{Al}}_2{\mathrm{O}}_3\to \mathrm{Al}$
• D. ${\mathrm{Cu}}_2\mathrm{O}\to \mathrm{Cu}$

Answer 1

The correct option is C

${\mathrm{Al}}_2{\mathrm{O}}_3\to \mathrm{Al}$

Explanation for the correct option:

Option (c):

• The process by which the roasted metal oxide is reduced to metals by heating at a high temperature in the presence of carbon is called smelting or reduction.
• Usually, metals like zinc, copper, and iron undergo this process.
• Aluminium oxide undergoes electrolytic reduction and gives aluminium.
• So, option (c) does not undergo reduction with coke.

Explanation for the incorrect option:

Option (a):

• The iron oxide is mixed with carbon (coke or coal) where it is heated at a high temperature to give the free metal iron.
• $$\begin{gathered} {\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+3\mathrm{C}\left(\mathrm{s}\right)\to 2\mathrm{Fe}\left(\mathrm{s}\right)+3\mathrm{CO}\left(\mathrm{g}\right) \\ {\mathrm{Fe}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+3\mathrm{CO}\left(\mathrm{g}\right)\to 2\mathrm{Fe}\left(\mathrm{s}\right)+3{\mathrm{CO}}_2\left(\mathrm{g}\right) \end{gathered}$$
• So, this option is reduced with the presence of coke.

Option (b):

• The zinc oxide is also mixed with carbon (coke or coal) where it is heated at a high temperature to give the free metal zinc.
• So, this option is reduced with the presence of coke.

Option (d):

• The free metal copper is formed by the mixture of carbon with copper oxide.
• So, this option is reduced with the presence of coke.

Final answer:

Hence, option (c) is the correct answer.