chemistry 問題

All metal hydroxides have basic property. This is because all metal hydroxides are ionic, and the hydroxide ions in metal hydroxides can react with hydrogen ions to give water.
Zn(OH)2(s) + 2H+(aq) → Zn2+(aq) + 2H2O(l)
Cu(OH)2(s) + 2H+(aq) → Cu2+(aq) + 2H2O(l)
Fe(OH)2(s) + 2H+(aq) → Fe2+(aq) + 2H2O(l)
Ca(OH)2(s) + 2H+(aq) → Ca2+(aq) + 2H2O(l)

Some metal hydroxides (including Zn(OH)2, Al(OH)3 and Pb(OH)2) are said to be amphoteric (兩性的). Like other metal hydroxide, amphoteric hydroxides can dissolve in strong acids. However, amphoteric hydroxides can also dissolve in strong alkalis because they with excess hydroxide ions in strong alkalis to form soluble anions. For example, zinc hydroxide can react with excess hydroxide ions to form soluble zincate ions.
Zn(OH)2(s) + 2OH-(aq) → [Zn(OH)4]2-(aq)
Other amphoteric hydroxides dissolve in strong alkalis in a similar way.
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