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a) A weak acid, HX, is 1.3% ionized in .20 M solution. What percent of HX is ionized in a .030 M solution? b) Does the percent ionization increase or decrease upon dilution? c) Does the H3O+ concentration of the above weak acid increase or decrease?

  • Chem -

    Please help, struggling like crazy.

  • Chem -

    HX <-> H+ + X-

    Concentration = mol/vol
    Since we only know mol and not concentration, we can just use mol since it is directly proportional to concentration
    HX H+ X-
    I 0.2 0 0
    C -y +y +y
    E 0.2-y y y

    Since y is very small(weak acid) Equilibrium mol for HX is 0.2

    Ionization % = [H+]eq/[HX]i *100%
    For 0.2M, [H+] = 1.3% / 100% * 0.2= 2.6*10^-5
    y=2.6*10^-5 M

    Now we can calculate Ka of HX
    Ka = [H+][X-] / [HX]

    ICE table for 0.03M
    HX H+ X-
    I 0.03 0 0
    C -z +z +z
    E 0.03-z z z
    (Once again, HX at equi = 0.03)

    Using Ka = [H+][X-] / [HX]
    1.3*10^-4 = z^2/0.03
    z=1.97*10^-3 = [H+]

    Ionization % for 0.03M =1.97*10^-3/0.03 *100%

    I'm not too sure if this is correct, haven't done this is awhile and quite rusty
    (Do check the calculations too)

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