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How to choose a reduced or oxidated form in a redox

  1. Feb 8, 2012 #1
    Hi guys i'm studying about general chemistry in a physics class.
    I've some exercices that i'm unable to solve, stuff like this:

    Copper can be solubilizated in water, oxidating in Cu++ form, reacting with HCrO4- in an acid enviroment realized by H2SO4. Write down the balanced reaction.

    my problem is to write (not to balance) an reduction/oxidation reaction.

    The copper is oxidating, so cromium or hydrogen have to reduce. I've thought about 3 different reaction.
    So, in my proposal, the unbalanced reaction are:

    Cu + HCrO4- -> Cu++ + Cr2O3 + H2O
    Cu + HCrO4- -> Cu++ + CrO + H2O
    Cu + HCrO4- -> CuCrO4 + H2

    how to choose the correct one?
  2. jcsd
  3. Feb 8, 2012 #2


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    Staff: Mentor

    Cr usually gets reduced to Cr3+ in such situations. You are probably right about copper chromate precipitation.

    Please note: copper is not "oxidating", copper is "being oxidized" while chromium is being reduced.
  4. Feb 8, 2012 #3
    Thanks for the reply :) :) .

    But how can i learn what usually a species does? :O
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