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Homework Help: Quick Question about theory in solving Ksp?

  1. Feb 6, 2016 #1
    1. The problem statement, all variables and given/known data

    Lead chromate, PbCrO4, is a yellow pigment used in paints. Suppose 0.50 L of a 1.0 x 10-5 M Pb(C2H3O2) and 0.50 L of a 1.0 x 10-3 M K2CrO4 solution are mixed. Calculate the equilibrium concentration of Pb+2 ion remaining in the solution after PbCrO4 precipitates. What is the percentage of Pb+2 remaining in solution after the precipitation has occurred. (The Ksp for PbCrO4 is 1.8 x 10-14)

    I have a little question regarding theory about how a website solved this problem.
    2. Relevant equations
    The solution is here on page 21 of the document.

    3. The attempt at a solution

    My question is this: is it really necessary to assume initially that this is a limiting reagent problem and have the reaction of Pb2+ and CrO42- go to completion to form the salt and then do the ICE chart calculation for the solubility, or is it OK if I just go and do the ice chart straight away?

    I tried both methods, and both gave the same numerical answer, but which approach is more "legit"?

    Thanks in advance.
  2. jcsd
  3. Feb 8, 2016 #2


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    Science Advisor
    Homework Helper
    Gold Member

    "ICE?" If you have to use it to satisfy "OC" types, do so. Otherwise, plug it in and grind it out.
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