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Homework Help: Equilibrium Lab

  1. Mar 21, 2009 #1
    1. The problem statement, all variables and given/known data

    COCL4 + 6H2 <=> Co(H20) +4CL

    blue <=> pink

    Question: Add a very small amount of AgNO3 to test tube #6. Stopper the test tube and shake.

    The solution in test tube turned pink, so I interpreted that as a shift to the products. Also, a precipitate (proper term? a solid was present...) formed.

    3. The attempt at a solution

    Now I have to offer an explanation for why this occurred. It seems as though the Ag+ is slightly soluble in Cl-, and the Cl is found on the product side, so was the Cl consumed somehow and thus produced CoCl42-?

    To me that doesn't seem reasonable.

    EDIT: I somehow thought myself into a circle, because CoCl42- wouldn't have been produced, for if it had the solution should have turned blue right? I'm fairly sure my explanation should hinge on the fact that Ag+is only slightly soluble with Cl-, but I don't want to go off on a tangent either, so if I'm horribly misguided please advise.
    Last edited: Mar 21, 2009
  2. jcsd
  3. Mar 21, 2009 #2
    I'm using this thread as a sort of running journal. If that is unacceptable, for some reason, please do inform me.

    New equation:

    2AgNO3(s) + 6H2O(al) + 2CoCl4(al)2- <=> Co(h2O)6(al)2+ + 8Cl(al)- + Co(NO3)2 (al) + 2Ag (s) + energy

    How many different ways can the equilibrium be shifted to the right? i.e. Removal of product, addition of reactant and removal of energy.
  4. Mar 21, 2009 #3
    The charges on the new equation don't balance. Looks like more Co(H20)6 (al) 2+ will have to be produced, and if that holds true then I can explain the colour change.
  5. Mar 21, 2009 #4


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    Staff: Mentor

    None of the reaction you have written so far is correct.

    What happens in the solution containing Ag+ and Cl-?
  6. Mar 21, 2009 #5

    CoCl42- + 6HOH + 4AgNO3(s) <=> Co(HOH)62+ + 4AgCl(s) + 4NO3- + energy

    Is this equation correct?
  7. Mar 21, 2009 #6


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    Staff: Mentor

    Much better, but not necesarilly correct.

    AgNO3 is well soluble. And no need to put some fancy looking dihydrogen monoxide HOH in the equation :wink:
  8. Mar 21, 2009 #7
    Doesn't HOH = H2O? I just found it easier to type HOH, so I did. Thanks for the help.
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