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Solubility Combining Ionic Equations,

  1. Feb 11, 2009 #1
    1. The problem statement, all variables and given/known data

    Consider the following equilibria at T = 26 0C, in which all ions are aqueous:
    Ag+(aq) + Cl-(aq) ----> AgCl(aq) K1 = 2.0E2
    AgCl(s) ----> Ag+(aq) + Cl-(aq) K2 = 1.9E-10

    Consider the reaction
    AgCl(s) ----> AgCl(aq)

    and calculate the concentration of AgCl(aq) in equilibrium with excess undissolved solid AgCl(s).

    Hint: calculate K3 first and use the equilibration constant expression to find the concentration of AgCl(aq).

    2. Relevant equations
    Ksp = [AgCl] I thinK?

    3. The attempt at a solution

    So I think I'm on the right track but missing something

    To get k3 is just combining k1 and k2, Since they easily cancel out to make AgCl(s) -> AgCl (aq), I think k3 is just 200 + 1.9E-10 = 200

    k3 = 200? That seems odd but then even if that is true I'm not sure which is next as with solubility I've always had problems where it is Ksp=[A], but this one is just Ksp=[A] as solids wouldn't count right?
  2. jcsd
  3. Feb 11, 2009 #2


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    Staff: Mentor

    No. First, try to write corect formulas for both Kso and complex formation. Just as if there were no other reactions.
  4. Feb 11, 2009 #3
    Oh I was thinking about it wrong.

    Is this correct?

    Ag+ + Cl- -> AgCl(aq) k1 = [AgCl]/[Ag+][Cl-]= 2E2
    AgCl(s) -> Ag+ + Cl- k2 = [Ag+][Cl-] = 1.9E-10

    K3 = k1 k2 = [AgCl(aq)] = 3.8E-8

    AgCl(aq) = 3.8E-8 mol/L ?

    The last part is only thing I'm not sure about.
    Last edited: Feb 11, 2009
  5. Feb 12, 2009 #4


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    Staff: Mentor

    Kso*Kf, looks OK to me.
  6. Feb 12, 2009 #5
    Yes thank you it was right. I appreciate the help.
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