Question

Name the following:

A compound that is added to lower the fusion temperature of the electrolytic bath in the extraction of aluminum.

Answer 1

• The ore of Aluminum is Bauxite($\mathit{A}{\mathit{l}}_{\mathbf{2}}{\mathit{O}}_{\mathbf{3}}\mathbf{.}\mathbf{2}{\mathit{H}}_{\mathbf{2}}\mathit{O}$).
• In Baeyer's process, bauxite is treated with Sodium hydroxide$\left(\mathrm{NaOH}\right)$ and Sodium aluminate$\left({\mathrm{NaAlO}}_2\right)$ is formed which is filtered off. The filtrated on heating with water gives Aluminium hydroxide$\left(\mathrm{Al}{\left(\mathrm{OH}\right)}_3\right)$ which gives alumina $\mathit{\left(}\mathit{A}{\mathit{l}}_{\mathbf{2}}{\mathit{O}}_{\mathbf{3}}\mathit{\right)}$ on strong heating.
• Alumina has high thermal resistance so for reducing the melting point of alumina, Cryolite($\mathit{N}{\mathit{a}}_{\mathbf{3}}\mathit{A}\mathit{l}{\mathit{F}}_{\mathbf{6}}$) and Calcium fluoride$\mathit{\left(}\mathit{C}\mathit{a}{\mathit{F}}_{\mathbf{2}}\mathit{\right)}$ is added.

Hence, the compound that is added to lower the fusion temperature of the electrolytic bath in the extraction of aluminum is Cryolite and Calcium fluoride.