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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: xstrae on November 10, 2006, 02:18:32 PM

Title: Simple question
Post by: xstrae on November 10, 2006, 02:18:32 PM

Hi, This might sound really basic but my teacher and myself had a long discussion on this. So I thought I will get your opinion on it.

Why is Zn(OH)₂ amphoteric while NaOH is basic?

thanks.

Title: Re: Simple question
Post by: DevaDevil on November 10, 2006, 04:05:37 PM

Because Zn(OH)₂ can either release the OH^--ions and form Zn²⁺(aq) + OH^-(aq), or take OH^- from the solution forming a complex: Zn[(OH)₄]^2-

In acids, it will react following the first hence increasing the pH, in bases it will follow the 2^nd, hence lowering the pH

NaOH will not form complexes, so can only react as a base.