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Homework Help: Acid-Base Equilibria

  1. Jan 4, 2014 #1
    Why is it that for the constant Kb, we always have to write H2O in the equation and we can omit H2O in acid reactions:

    My textbook always writes:
    NH3+H2O<=>NH4++OH-
    NH4+<=>NH3+H+

    Why can we not write NH3+H+<=>NH4+?
     
  2. jcsd
  3. Jan 4, 2014 #2

    Borek

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    Staff: Mentor

    We can. NH4+ is a weak acid, with a dissociation constant of 5.6×10-10, and above dissociation reaction is perfectly valid.

    Your book my be sticking to one convention to make things easier to follow.
     
  4. Jan 4, 2014 #3
    Would the equilibrium constant be the same of that reaction? Or should we substitute OH- with Kw/H+?
    Kw=10^-14
     
  5. Jan 4, 2014 #4

    Borek

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    Staff: Mentor

  6. Jan 4, 2014 #5
    I guess this means yes. :)
     
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