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Balancing Chemical Equations Using Oxidation Numbers

  1. Dec 11, 2009 #1
    1. The problem statement, all variables and given/known data

    http://carlodm.com/pictures/problem.png [Broken]

    3. The attempt at a solution

    I'm stuck. Usually I balance the equation by multiplying the Fe(OH)2 and Fe2O3 by 3. However, I can no longer do this because Fe2O3 has two iron's per one molecule.

    Do I multiply one by 6 and the other by 3?
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Dec 11, 2009 #2

    Borek

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    Staff: Mentor

    Assume 2Fe(OH)2 is your reagent (why? because Fe2O3 contains two Fe atoms, just keep iron atoms forming one molecule of product togehter) - then you will have to multiply everything by 3. Basically that's the same as multiplitcation by 3 & 6, but it is easier to follow the reasoning.

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  4. Dec 11, 2009 #3
    I see. So I should balance the reactant iron first, to 2... then do the multiplications of irons by 3.

    I've arrived at that step but the products side still looks like a mess. Is this where I stop all "techniques" and rely on intution and trial and error to figure out the balanced equation?
     
  5. Dec 11, 2009 #4

    Borek

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    Staff: Mentor

    Once you have Fe and Cr balanced rest you have to "balance by inspection" - which, as you have correctly pointed out, is a fancy name for "intuition and trial and error" :wink:

    Do you have to use ON method?

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  6. Dec 11, 2009 #5
    No we're not required to use the ON method... but it is a tool that we are able to utilize for ugly equations such as this. Thanks for your help! This'll come handy for reviewing my Chem exam.
     
  7. Dec 11, 2009 #6

    Borek

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    Staff: Mentor

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