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Ionisation constants

  1. Mar 2, 2006 #1
    If 6.8 * 10-4 is ionisation constant(IC) of HF, what is the IC of its conjugate base.

    HF +H2O -----> H3O+ +F-
    So F- is the conjugate base(CB)
    I figured the IC of CB would be the reciprocal of IC of HF. But the answer given is the same but multiplied by Ionic product of water i.e. 10-14

    Please explain why
  2. jcsd
  3. Mar 6, 2006 #2


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    Ionisation of the conjugate base? Isn't it already ionised?

    Perphaps you mean the basicity constant for the equilibirium
    F- + H2O ----> HF + OH-

    In that case, won't it be Kw/Ka?
    Last edited: Mar 6, 2006
  4. Mar 6, 2006 #3


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    yep, that's what is meant the ionization constant, in this problem. For the base it can also be called the hydrolysis constant, Kb
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