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Homework Help: Chem Lab Help: Equilibrium Systems

  1. Dec 5, 2007 #1
    1. The problem statement, all variables and given/known data
    Explain what happened when the solution was added to water in terms of Le Chatelier's principle and ocument your explanation using observations. Think Carefully! write out the correct mass action expression before you answer--this is subtle!

    2. Relevant equations
    a. BiCl3(s) ↔ Bi^3+(aq) + 3Cl-(aq)
    b. Bi^3+(aq) + Cl-(aq) + H2O(l) ↔ BiOCl(s) + 2H+(aq)
    c. BiCl3(s) + H2O(l) ↔ BiOCl(s) + 2HCl(aq)

    3. The attempt at a solution
    Mass Action: 1* [HCl]^2 / 1 * 1
    The 1's are because the solids and liquids are not counted in mass action expressions.

    My observations were that HCl to the system got rid of the white precipitate of BiOCl making a clear solution of disolved BiCl3 in water. I observed that after adding water the precipitate reformed. My original theory was that the added concentration of H20 shifted the equation to the right because of the added concentration of H20, however, because H20 is not a part of the mass action expression, I changed my theory to be:

    The adding of water causes the HCl to become dilute and less concentrated, shifted the equation to the right to counteract the change in the system.

    Is this the right theory? I have heard a bunch of different ideas from my classmates, but I like my idea the best, but I'm not sure if this is the right answer.
  2. jcsd
  3. Dec 11, 2007 #2


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    Sounds good.
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