# Goldschmidt alumino-thermic process

I recently came across this question in a book.

Among the metals $\ce{Cr}$, $\ce{Fe}$, $\ce{Mn}$, $\ce{Ti}$, $\ce{Ba}$ and $\ce{Mg}$, the one that cannot be obtained by reduction of its metal oxide by aluminum is:-
(a) $\ce{Cr}$
(b) $\ce{Fe}$
(c) $\ce{Mn}$
(d) $\ce{Ba}$
(e) $\ce{Mg}$

So, one method to answer this question is by Ellingham Diagram and to remember the values of $\Delta G^0$(Gibbs free energy change) for oxidation of each metal into its oxide and it's variation with temperature.

So, we can see that $\Delta G^0$ for oxidation of $\ce{Al}$ is much lower than other metals except $\ce{Mg}$ at lower temperatures. Thus, $\ce{Al}$ can reduce other metals except $\ce{Mg}$ at lower temperatures.
Thus, the answer is (e) $\ce{Mg}$.
So, this was the answer based on the experimental data for metals.
Couldn't we determine this answer theoretically as we can't remember all these data?

• The metal reactivity series is pretty fundamental to remember. The series would be (K,Na,Mg,Al,Zn,Fe,Cu,Ag,Au,Pt) to name a few – Pritt Balagopal Apr 21 '17 at 15:59
• But, there aren't all the metals in your mentioned reactivity series like Cr, Mn, Ca, Ba, Ti etc. Can you please mention the whole reactivity series. – Prashant Kumar Apr 21 '17 at 16:33
• Wikipedia has an entire page about it: en.m.wikipedia.org/wiki/Reactivity_series – Pritt Balagopal Apr 21 '17 at 16:35