Write a balanced equation for when zinc metal reacts with an aqueous hydroxide ions.

A gas and a complex ion is formed

Answer and explanation; Zinc metal reacts with strong bases forming hydrogen gas:

Zn (s) + 2 OH - (aq) → Zn (OH) 2 (s) + H2 (g)

Zn2 + is precipitated by hydroxide ions as Zn (OH) 2 (white amorphous precipitate)

Zn2 + (aq) + 2 OH - (aq) ⇄ Zn (OH) 2 (s)

By acid excess hydroxide ions, the precipitate is dissolved.

Zn (OH) 2 (s) + 2 H + (aq) ⇄ Zn2 + (aq) + 2 H2O (l)

Zn (OH) 2 (s) + 2 OH - (aq) ⇄ [Zn (OH) 4]2 - (aq)

[Zn (OH) 4]2 - (aq) is the complex ion