Ellingham Diagram and Reduction of Alumina

An Ellingham diagram is a graphical representation that shows the thermodynamic stability of various metal oxides with respect to temperature. It is used to determine the feasibility of a reduction reaction between a metal oxide and a reducing agent.

Alumina (Al2O3) is a metal oxide commonly found in minerals such as bauxite. It is used in various industries, including the production of aluminum metal.

To reduce alumina to aluminum metal, a suitable reducing agent is required. The reducing agent should have a lower Gibbs free energy of formation for its oxide compared to that of alumina. This means that the reducing agent should be able to more readily form its oxide compared to alumina.

Possible Reducing Agents:

a) Fe (Iron):
- Iron has a higher Gibbs free energy of formation for its oxide (Fe2O3) compared to alumina (Al2O3). Therefore, iron is not a suitable reducing agent for alumina.

b) Zn (Zinc):
- Zinc has a lower Gibbs free energy of formation for its oxide (ZnO) compared to alumina (Al2O3). Therefore, zinc is a suitable reducing agent for alumina.

c) Mg (Magnesium):
- Magnesium has a lower Gibbs free energy of formation for its oxide (MgO) compared to alumina (Al2O3). Therefore, magnesium is a suitable reducing agent for alumina.

d) Cu (Copper):
- Copper has a higher Gibbs free energy of formation for its oxide (Cu2O) compared to alumina (Al2O3). Therefore, copper is not a suitable reducing agent for alumina.

Conclusion:

Based on the Ellingham diagram and the comparison of the Gibbs free energy of formation for the oxides, magnesium (Mg) is the most suitable metal to reduce alumina (Al2O3) to aluminum metal.