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    Within Chemistry

    1. Periodicity

    Metal oxides usually form basic solutions in water; aqueous solutions of nonmetal oxides are acidic.
    The acidity of the hydrogen halides increases in the sequence
    The basicity of Period 3 hydroxides decreases in the sequence
    The acidity of Period 3 oxyacids increases in the sequence
    2. Solutions/solubility
    Most acids tend to be water soluble. NaOH and KOH are quite soluble in water. Ca(OH)2 is moderately water soluble. Acidic solutions dissolve some metals (Fe, Zn, and Al), releasing hydrogen gas. Zinc and aluminum will dissolve in base. Drano(TM) consists of solid NaOH and Al turnings. When water is added to the mixture, hydrogen gas is evolved.
    3. Equilibrium; Ionization Constant
    The dissociation of a strong acid or base is complete. The ionization constant expression is a measure of the equilibrium for the ionization of a weak acid or base. For example, the equilibrium established when the weak acid, acetic acid, ionizes,

    is given by the ionization constant expression:



    Water has the important characteristic of being able to act as either an acid or base. This tendency allows two water molecules to react accordingly
    The equilibrium constant expression for the process is
    Kw, the ion product constant for water, has a value of 1.0 x 10-14 at 25 oC and 2.4 x 10-14 at 37 oC (body temperature). This is significant because it means that although at 25 oC a neutral solution has a pH = 7, at 37 oC, the pH of a neutral solution is less than 7 (6.81).

    Acids and Bases
    (Page 31)

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