Question

The correct statements with respect to Ellingham's diagram among the following are
(I) Magnesium reduces aluminium oxide below 1700 K
(II) Aluminium reduces magnesium oxide above 1700 K
(III) Aluminium reduces magnesium oxide below 1700 K
(IV) Magnesium reduces aluminium oxide above 1700 K

• A. I & II
• B. II & III
• C. III & IV
• D. II, III & IV

Answer 1

The correct option is A I & II

The correct statements with respect to Ellingham's diagram are I & II
(I) Magnesium reduces aluminium oxide below 1700 K.
Below 1700 K, $\Delta G^o$ for the reaction $2Mg+O_2\to 2MgO$ is more negative than $\Delta G^o$ for the reaction $\frac{4}{3}Al+O_2\to \frac{2}{3}A{l}_2{O}_3$
(II) Aluminium reduces magnesium oxide above 1700 K
Above 1700 K, $\Delta G^o$ for the reaction $2Mg+O_2\to 2MgO$ is less negative than $\Delta G^o$ for the reaction $\frac{4}{3}Al+O_2\to \frac{2}{3}A{l}_2{O}_3$
More negative the value of $\Delta G^o$, the greater is the tendency of the element to combine with oxygen.
Hence, the option (A) is the correct answer.