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Homework Help: Testing Le Chatelier's Principle

  1. Dec 15, 2016 #1
    1. The problem statement, all variables and given/known data
    During class we did a lab testing Le Chatelier's Principle where we took FeSCN-(aq) and added water in order to dilute it to a lighter colour (red to orange) and to make a stock solution. We then divided the stock solution into several test tubes. In one of them we added KSCN.

    The question asked is:

    How does the concentration of Fe3+(aq), SCN-(aq) and FeSCN2+(aq) change if the KSCN is added to the test? What remains constant? What kind of shift is involved?

    2. Relevant equations

    3. The attempt at a solution

    I just need clarification to see if I'm doing this correctly. When we add KSCN to a test tube with the stock solution the solution went from orange to yellow. When it asks about how the concentration changes, it changes because there is more KSCN added. Meaning there will be more SCN-(aq), would this be correct? Pertaining to the question what remains constant would that just simply be the iron? And lastly what kind of shift involved would be a shift to the left because it favors the reactants.
  2. jcsd
  3. Dec 16, 2016 #2


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    Staff: Mentor

    You have changed the total volume, how can the iron concentration remain constant?

    I can be wrong, but at a first sight looks like the experiment is a bit misleading. Color change is most likely effect of dilution, not of a shift in the reaction.
  4. Dec 16, 2016 #3
    Oh okay that makes sense
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