Question

Why does aluminium hydroxide dissolved in excess sodium hydroxide

Answer 1

Sodium hydroxide (NaOH) is a base that reacts with aqueous solutions containing metallic ions. Let's assume that all of our solutions are metallic sulfates. The sulfate ion (SO4 -2) is a spectator ion because it isn't involved in the reaction with sodium hydroxide, which means we can ignore it. The sodium ion in sodium hydroxide is also a spectator ion, so we won't include it the equations of the reactions either.

The metallic ions bond with the hydroxide ion (OH-) and a precipitate is formed, which is a solid. Precipitates look like milk or milk dyed with food coloring when it's dropped into water. The type of precipitate formed helps identify the metallic ion present.