Chemistry - Metallurgy Question with Solution | TestHub

A is correct: In the Baeyer's process, red bauxite is treated with concentrated NaOH. The Al₂O₃ dissolves to form soluble sodium aluminate, while the Fe₂O₃ impurity remains insoluble and is removed as "red mud."

B is correct: Adding Cryolite (Na₃AlF₆) and Fluorspar (CaF₂) to alumina lowers the fusion temperature from $2323K$ to about $1173K$ and provides the necessary ions to increase the electrical conductivity of the melt.

C is correct: Gold extraction uses the Mac-Arthur Forrest cyanide process, where gold is leached into a soluble complex $[Au(CN{)}_2{]}^{-}$ and then recovered through a displacement reaction (reduction) using Zinc scrap.

D is correct: Magnesium is a highly electropositive metal with a very stable oxide. It cannot be reduced by its own sulfide or oxide (self-reduction); instead, it is obtained via the electrolysis of fused anhydrous magnesium chloride.