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Homework Help: Chemistry - Titration, Redox, Combining Equations

  1. Oct 21, 2006 #1
    The attachment shows reactions involved in a titration experiment. In the first equation, iodate reacts with iodide in acidic solution to produce iodine. In the second equation, the iodine is titrated with thiosulfate.

    I know the volume and molar concentration of iodate as well as the volume of thiosulfate as determined by the titration. I need to find the molar concentration of thiosulfate.

    I think I need to balance each equation separately by breaking them into oxidation/reduction reactions.

    I am then instructed to combine the balanced equations [1] and [2], in that order. Is this as simple as it sounds where I can just add them together, cancel out anything that appears on both sides of the equation, etc.? Why does order matter?

    Thanks for any help!

    Attached Files:

  2. jcsd
  3. Oct 21, 2006 #2
    You wont be able to comibine anything untill your electrons cancel out. You have to start with the half reactions and balance those. Then you have to make sure each reaction has the same number of electrons. Then you can cancel things out to get your final equation. It wouldnt be balanced if you didnt start from the start. (i dont mean that in any sarcasm)

    I hope this makes sense
  4. Oct 21, 2006 #3
    That makes sense... so I got to where I balanced equation [1] by writing half reactions and cancelling out electrons to get the balanced equation, say [1.5]. And I balanced [2] to get [2.5].

    Now I am asked to combine [1.5] and [2.5], in that order. But I'm not sure how to do that? Can I just put all the reactants and all the products of both equations together and then cancel out things that appear on both sides?
  5. Oct 21, 2006 #4
    You can do this when and only when your electrons are the same on the OPPOSITE sides of the equations. Just using caps for emphasis.
  6. Oct 22, 2006 #5
    Thanks, I got the answer
  7. Oct 22, 2006 #6
    Awesome :biggrin:
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