Balancing Chemical Equations Using Oxidation Numbers

  • #1

Homework Statement



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

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?
 
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Answers and Replies

  • #2
Borek
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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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  • #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?
 
  • #4
Borek
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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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  • #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.
 
  • #6
Borek
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