Question

Considering Ellingham diagram, which of the following metals can be used to reduce alumina ?

• A. Fe
• B. Mg
• C. Zn
• D. Cu

Answer 1

The Correct Option is B

To determine which metal can be used to reduce alumina (Al₂O₃) by referring to the Ellingham diagram, we need to understand the basic principle of the Ellingham diagram. The Ellingham diagram provides a graphical representation of the temperature dependence of the standard Gibbs free energy change (ΔG°) for the formation of oxides from elements. The more negative the ΔG°, the more stable the oxide.

1. The reduction process can be described by the general oxidation-reduction equation:

   2Al + 3/2O_2 \rightarrow Al_2O_3

2. In order to reduce alumina, a metal is required that can form a more stable oxide than Al₂O₃. This means that the ΔG° for the formation of the metal oxide must be more negative than that of Al₂O₃.
3. Let's consider the metals from the options: Fe, Mg, Zn, and Cu.
4. Looking at the typical Ellingham diagram:
   • Magnesium (Mg): The line for MgO is below the line for Al₂O₃, which means that Mg can reduce alumina effectively because MgO is more stable than Al₂O₃.
   • Iron (Fe), Zinc (Zn), and Copper (Cu): The lines for FeO, ZnO, and CuO are above the line for Al₂O₃, indicating that alumina is more stable than these oxides, and hence, they cannot reduce alumina.
5. Therefore, the correct answer is Mg (Magnesium), as it can reduce alumina by forming a more stable oxide, MgO.

In conclusion, when considering the Ellingham diagram for this reduction process, magnesium (Mg) is the correct choice to reduce alumina, since it can form a more stable oxide than alumina itself.