Final answer:
The precipitate that forms from a solution of aluminum nitrate during the third step is aluminum hydroxide, Al(OH)3. This precipitate can then be processed further into aluminum oxide, Al2O3, for use in the electrolysis to produce aluminum metal.
Step-by-step explanation:
The product of the precipitate that forms from a solution of aluminum nitrate during the third step of the scheme provided is aluminum hydroxide, Al(OH)3. When Na[Al(OH)4](aq) reacts with H3O+ (aq), aluminum hydroxide precipitates out of the solution as represented by the reaction Na[Al(OH)4](aq) + H3O+ (aq) → Al(OH)3 (s) + Na+ (aq) + 2H₂O(l). The next steps involve removing the precipitate by filtration and then further processing it by heating to produce aluminum oxide, Al2O3, which is then used in the electrolysis to produce aluminum metal.
It's important to note that during the electrolysis, aluminum oxide dissolves in a molten mixture of cryolite (Na3AlF6) and calcium fluoride (CaF2), where reduction occurs at the cathode to form aluminum metal and oxidation occurs at the anode, producing gases such as oxygen, carbon monoxide, and carbon dioxide.