Question

What is the function cryolite in the extraction of $\mathrm{Al}$, other than dissolving bauxite.

Answer 1

Function of cryolite in the extraction of $\mathbf{Al}$ :

• In the extraction of aluminium, alumina $\left({\mathrm{Al}}_2{\mathrm{O}}_3\right)$ is added to the cryolite $\left({\mathrm{Na}}_3{\mathrm{AlF}}_6\right)$ because it lowers the melting point of alumina from $2050°\mathrm{C}$to $950°\mathrm{C}$.

$$\begin{gathered} {\mathrm{Na}}_3{\mathrm{AlF}}_6\left(\mathrm{aq}\right)\to 3{\mathrm{Na}}^{+}\left(\mathrm{aq}\right)+{{\mathrm{AlF}}_6}^{3-}\left(\mathrm{aq}\right) \\ {\mathrm{Al}}_2{\mathrm{O}}_3\left(\mathrm{s}\right)+4{{\mathrm{AlF}}_6}^{3-}\left(\mathrm{aq}\right)\to 3{\mathrm{Al}}_2{{\mathrm{OF}}_6}^{2-}\left(\mathrm{aq}\right)+6{\mathrm{F}}^{-}\left(\mathrm{aq}\right) \end{gathered}$$

• It enhances the conductivity of the electrolytic solution.

Hence, the function of cryolite in the extraction of $\mathbf{Al}$ is to enhance the conductivity and lowers the melting point of alumina.