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Oxidation and reduction problems

  1. Feb 3, 2013 #1
    When something is oxidized, it gains oxygen, loses hydrogen or loses electron. However, if the substance gains something else other than oxygen then it won't be considered oxidation anymore? For instance H+ +OH- -->H2O so in this case it seems that the H+ gained oxygen from OH- but actually the H+ ion was not oxidized as the full reaction is HCl+NaOH-->H2O+NaCl so the compound containing the hydrogen ion aka HCl lost the chlorine and gains oxygen so it was not oxidized?

    So is saying a compound gains oxygen too vague? Because if the substance loses and gains something else other than oxygen then the substance might not be oxidized at all? I think it would apply for the gain or lost in hydrogen as well. Because it appears that the hydroxide ion gained another hydrogen, however it was not reduced.

    That being said when Cr2O7 2- +14H+ +6e-->2Cr3+ +7H2O, how are we going to explain how it became reduced?

    We can't use the gain of hydrogen as Cr3+ does not contain any hydrogen and cant use the lost in oxygen as besides losing oxygen it lost a cation in Cr2O7 2- and gained an anion in Cr3+. So how should I explain its reduction without using oxidation states?

    Thanks for the help :)
     
  2. jcsd
  3. Feb 3, 2013 #2
    Oxidation is loosing electrons, reduction is gaining them.
     
  4. Feb 4, 2013 #3
    Oh but can i say the Cr2O7 2- gains electrons? Since the actual base equation given is oxidant+electron(s) ->product.

    Thanks for the help :)
     
  5. Feb 4, 2013 #4
    Another way of seeing it is: Cr6+ + 3e- -> Cr3+
     
  6. Feb 4, 2013 #5
    Hi thanks for the reply :smile:

    Oh I didn't know I could do that. But in this case is it possible for me to explain it by losing oxygen?
     
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