Addition of aqueous ammonia to a solution of Zn++ gives a white precipitate which dissolves in an excess of ammonia because?

Addition of aqueous ammonia to a solution of Zn++ gives a white precipitate which dissolves in an excess of ammonia because?

Answer Details

The addition of aqueous ammonia to a solution of Zn^++ gives a white precipitate of zinc hydroxide (Zn(OH)2), which dissolves in excess ammonia to form a colorless, water-soluble complex ion called tetraamminezinc(II) ([Zn(NH3)4]^(2+)). This happens because zinc hydroxide is an amphoteric substance, which means it can react as an acid or a base. In the presence of aqueous ammonia, it acts as an acid and forms the complex ion which is readily soluble in water. Therefore, the correct answer is "zinc forms a complex which is readily soluble in excess ammonia."