electrochem question

Discussion in 'MCAT Study Question Q&A' started by echoyjeff222, Sep 7, 2014.

  1. echoyjeff222

    2+ Year Member

    Jun 17, 2013
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    Medical Student (Accepted)
    TBR passage XIV, number 90:

    upload_2014-9-7_20-36-26.png upload_2014-9-7_20-36-52.png

    I thought it was D because it directly says the final masses in the passage ... I don't get it? Is the time scale going past the 1 min in the experiment or something? I know the solution IV has a higher molarity, but I thought that would just result in a longer time of increasing mass ... help?
  2. mehc012

    mehc012 Big Damn Hero
    5+ Year Member

    Jul 9, 2012
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    Medical Student
    Well, you know it must be B or D because 1 reaches a higher mass at the end, right?

    So the real question is, which proceeds more quickly? Which reaches the final mass first?

    We tend to ignore concentration in these things, but it does make a difference. Here, it is the only difference which you are given any information on...you are not given the reduction potentials, so you can't be expected to make a judgement based on that. You DO know that the concentrations differ. So, would the one with a higher concentration of reactant be expected to react more or less quickly?
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    Cawolf likes this.

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