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Homework Help: Zn(OH)2 and Al(OH)3

  1. Nov 2, 2008 #1
    1. The problem statement, all variables and given/known data

    Basicly why are Zn(OH)2 and Al(OH)3 ampiprotic given that they give have a clear color when reacted with water and Phenolphthalein and given that when reacted with 6M HCl they are clear and when reacted with 6M of NaOH they are red.

    Note for Phenolphthalein red mean basic colourless means acidic.

    3. The attempt at a solution
    I get that they react as an acid when in water but to prove that they are ampiprotic you have to prove they react as a base with HCl which I cannot figure out how to do since they can also react as an acid with HCl increasing H+ ions still giving you coloirless color.
  2. jcsd
  3. Nov 3, 2008 #2


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    Staff: Mentor

    Your experimental setup didn't allow to conlcude anything about Al and Zn amphoterism.
  4. Nov 3, 2008 #3
    Oh i think i have to use the fact that there were precipitates
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