Which is the only white precipitate formed by reacting with sodium hydroxide solution that dissolves in excess?

The formation of a white precipitate that dissolves in excess sodium hydroxide solution is a characteristic behavior of aluminium hydroxide. When aluminium ions react with sodium hydroxide, they initially form aluminium hydroxide, which appears as a white precipitate. However, unlike some other metal hydroxides, aluminium hydroxide can dissolve in excess sodium hydroxide, forming a soluble complex called sodium aluminate.

This property is notable because it distinguishes aluminium hydroxide from other metal hydroxides that do not dissolve in excess hydroxide. For example, barium hydroxide remains soluble in water but does not form a precipitate in the same scenario, while copper and iron hydroxides form precipitates that are not soluble in excess sodium hydroxide, thereby maintaining their solid form. The ability of aluminium hydroxide to dissolve in excess sodium hydroxide and form a soluble species is key to identifying it as the only white precipitate with this specific characteristic in the given options.