Answer 1

In the extraction of aluminum, the given compound play the following roles

Sodium hydroxide:

Two roles are played by sodium hydroxide in the extraction of aluminum. First, finely grinded bauxite (ore of aluminum) is heated under pressure with conc. caustic soda solution (NaOH solution) for 2–8 hours at 140°C to 150°C to produce sodium aluminate. The chemical equation is as follows:

Al₂O₃.2H₂O + 2NaOH → 2NaAlO₂ + 3H₂O

Second, on diluting sodium aluminate with water and cooling to 50°C, sodium aluminate is hydrolyzed to give aluminum hydroxide as the precipitate. Here, the impurities dissolve in sodium hydroxide.