|MadSci Network: Chemistry|
We use the difference in reactions with 3 drops and then an excess of sodium hydroxide and ammonium hydroxide to show differences in the way certain metal ions react like Al, Zn, Mg. With three drops of ammonium hydroxide all three ions precipitate. With an excess of ammonium hydroxide Al and Mg are precipitated and Zn clears up. We noticed that if nitric acid is used it will clear up all of those that precipitate. If ammonium hydroxide is again added in excess the Al reprecipitates, the Zn first precipitates and then clears, but the "Mg never again forms a precipitate". We would like to use this idea to have our students see the presence of both Zn and Mg in an unknown solution, but we are looking for and explanation why the Mg never reprecipitates. Any help would be appreciated.
Re: Reaction of the magnesium ion with ammonium hydroxide
Try the links in the MadSci Library for more information on Chemistry.