Is it true that under certain conditions,
Question:

Is it true that under certain conditions, Mg can reduce SiO2 and Si can reduce MgO? What are those conditions?

Solution:

$\mathrm{Mg}_{(s)}+\frac{1}{2} \mathrm{O}_{2(g)} \longrightarrow \mathrm{MgO}_{(s)}\left[\Delta G_{\left(\mathrm{Mg}, \mathrm{M}_{8} \mathrm{O}\right)}\right]$

$\mathrm{Si}_{(s)}+\mathrm{O}_{2(g)} \longrightarrow \mathrm{SiO}_{2(s)}\left[\Delta G_{\left(\mathrm{Si}, \mathrm{SiO}_{2}\right)}\right]$

The temperature range in which $\Delta G_{(\mathrm{Mg}, \mathrm{Mg} \mathrm{o})}$ is lesser than $\Delta G_{\left(\mathrm{Si}, \mathrm{SiO}_{2}\right)}, \mathrm{Mg}$ can reduce $\mathrm{SiO}_{2}$ to Si .

$2 \mathrm{Mg}+\mathrm{SiO}_{2} \longrightarrow 2 \mathrm{MgO}+\mathrm{Si} ; \Delta \mathrm{G}^{\theta}=-$ ve

On the other hand, the temperatures range in which $\Delta G_{\left(\mathrm{Si}, \mathrm{si} \mathrm{O}_{2}\right)}$ is less than $\Delta G_{(\mathrm{Mg}, \mathrm{Mg} \mathrm{O})}$, Si can reduce $\mathrm{MgO}$ to $\mathrm{Mg}$.

$\mathrm{SiO}_{2}+2 \mathrm{Mg} \longrightarrow \mathrm{SiO}_{2}+2 \mathrm{Mg} ; \Delta \mathrm{G}^{\ominus}=-v \mathrm{e}$

The temperature at which ΔfG curves of these two substances intersect is 1966 K. Thus, at temperatures less than 1966 K, Mg can reduce SiO2 and above 1966 K, Si can reduce MgO.