Question

Study the Ellingham diagram for the formation of some oxides and answer the following question.
At the point of intersection of $A{l}_2{O}_3$ and $MgO$ curves (A), $△G^0$ becomes zero for the reaction,
$\frac{2}{3}A{l}_2{O}_3+2Mg\to +\frac{4}{3}Al$
Below this point, magnesium can reduce alumina. Although thermodynamically feasible, Al is not used for reduction of $MgO$ because:

• A. temperature required is very high
• B. the yields of metal is very low
• C. the value of $△G^0$ becomes positive
• D. magnesium is not used as reducing agent for any reaction

Answer 1

The correct option is A temperature required is very high

Temperatures above the point of intersection of $A{l}_2{O}_3$ and $MgO$ curves, Al can reduce MgO. But the temperature required would be so high that the process will be uneconomic and technology is difficult.