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Topic: Redox reactions - balancing  (Read 3219 times)

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Offline Shaun1979

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Redox reactions - balancing
« on: June 02, 2009, 11:06:40 AM »
Hi,

I understand redox reactions mostly, but I cannot seem to get this:

Question: Balance the equation for the reaction of dichromate ion with lead(II) ion to produce chromium(III) and other products.
Hint: The reaction takes place in acidic medium.

This is what I came up with for one of the half reactions:

Cr2O7(2-) = Cr(3+)

Cr2O7(2-) = 2Cr(3+)

Cr2O7(2-) = 2Cr(3+) + 7H2O

14H(+) + Cr2O7(2-) = 2Cr(3+) + 7H2O

6e- + 14H(+) + Cr2O7(2-) = 2Cr(3+) + 7H2O


That seems to make sense to me (unless I am wrong) .  but what I cannot seem to fathom is what these "other products" are that they are referring to in the question? Without which I can't do the other half? Maybe I am reading too much into it, but my textbook doesn't mention anything of the sort.

Any help would be greatly appreciated.



Offline Borek

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Re: Redox reactions - balancing
« Reply #1 on: June 02, 2009, 12:13:07 PM »
Water is already other product :)

Chromium got reduced, it reacted with Pb(II) - so the Pb(II) had to be oxidzed...
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Offline Shaun1979

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Re: Redox reactions - balancing
« Reply #2 on: June 02, 2009, 12:31:04 PM »
Thanks Borek!

That makes sense to me, I just don't understand how to go about writing that as a half reaction?



Offline AWK

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Re: Redox reactions - balancing
« Reply #3 on: June 02, 2009, 12:59:10 PM »
As far as I know this reaction is impossible but oxidation of Pb(II) to Pb(IV) can be performed in strongly alkaline solution with H2O2 or Br2.
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