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Characteristic Reactions of Zinc Ions (Zn²⁺)

  • Page ID
    97279
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    • Most common oxidation states: +2
    • M.P. 420o
    • B.P. 907o
    • Density 7.13 g/cm3
    • Characteristics: Zinc is a bluish-gray metal. Quite active; burns readily in air to form white \(\ce{ZnO}\) and combines with many nonmetals.

    Characteristic reactions of Zn²⁺

    Zinc(II) ion forms complex ions readily.

    Aqueous Ammonia

    Zinc(II) ion reacts with aqueous ammonia to precipitate white gelatinous Zn(OH)2:

    \[\ce{Zn^{2+}(aq) + 2NH3(aq) + 2H2O(l) <=> Zn(OH)2(s) + 2NH4^{+}(aq)}\] Al3ppt.gif

    The zinc(II) hydroxide precipitate dissolves in excess ammonia:

    \[\ce{Zn(OH)2(s) + 4NH3(aq) <=> [Zn(NH3)4]^{2+}(aq) + 2OH^{-}(aq) }\] Sr5b2.gif

    Sodium Hydroxide

    Sodium hydroxide also precipitates zinc(II) hydroxide:

    \[\ce{Zn^{2+}(aq) + 2OH^{-}(aq) <=> Zn(OH)2(s)}\] Al3ppt.gif

    The zinc(II) hydroxide precipitate also dissolves in excess hydroxide:

    \[\ce{Zn(OH)2(s) + 2OH^{-}(aq) <=> [Zn(OH)4]^{2-}(aq)}\] Sr5b2.gif

    Potassium Ferrocyanide

    A gray-white precipitate is formed with ferrocyanide ion. The precipitate may be blue-green if traces of iron ions are present:

    \[\ce{3Zn^{2+}(aq) + 2K^{+}(aq) + 2[Fe(CN)6]^{4-}(aq) <=> K2Zn3[Fe(CN)6]2(s)}\] Zn5.gif

    Note: Many metal ions form ferrocyanide precipitates, so potassium ferrocyanide is not a good reagent for separating metal ions. It is used more commonly as a confirmatory test.

    No Reaction

    \(\ce{Cl^{-}}\), \(\ce{SO4^{2-}}\)


    This page titled Characteristic Reactions of Zinc Ions (Zn²⁺) is shared under a not declared license and was authored, remixed, and/or curated by James P. Birk.

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