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Homework Help: Balancing a redox reaction

  1. Oct 15, 2011 #1
    I am supposed to balance the following reaction:
    CdS + HNO3 (dil) → Cd(NO3)2 + NO + S + H2O

    After writing out all the oxidation numbers for each atom, I found that Cd and N are both reduced (Cd5+ → Cd 1+ and N5+ → N2+).

    I am wondering how to approach this problem. Is it possible to have 2 atoms reduced? Is this what the dilute acid does?
  2. jcsd
  3. Oct 16, 2011 #2


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    Staff: Mentor

    Show how you calculated oxidation numbers for Cd and S.

    Yes, it may happen that more than one atom gets reduced or oxidized, but in such situations it usually means there are two separate, parallel processes going on - and they can be described by two reaction equations. However, for the redox reaction to proceed you need BOTH reduction and oxidation to be taking place at the same time. So if you have found only elements that are being reduced, there is for sure something wrong.
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