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Homework Help: Total # of electrons transferred

  1. Oct 26, 2005 #1
    Hello...
    Im working on a chemistry assignment for first year chem (university). The question says:
    What is the TOTAl number of electrons transferred when yje following equationis balanced (for acid media) with integer coefficients? Br2(l) + ClO3-(aq) + H2O(l) --> BrO3-(aq)+ Cl-(aq) + H+(aq)
    Sorry i woulda used the special writing thing buit i forget how to. I know i shoulda got help sooner and its due at 6am. so any help asap is appreciated.
     
  2. jcsd
  3. Oct 26, 2005 #2
    Br2(l) + ClO3-(aq) + H2O(l) --> BrO3-(aq)+ Cl-(aq) + H+(aq)
    1. Write the half reactions.
    ClO3- --> Cl-
    Br2 --> BrO3-
    2. Balance the atoms, leaving H and O for last.
    ClO3- --> Cl- + 3H2O
    Br2 + 6H2O --> 2BrO3-
    3. Balance H with hydrogen ions:
    6H+ + ClO3- --> Cl- + 3H2O
    Br2 + 6H2O --> 2BrO3- + 12H+
    4. Balance charge with electrons:
    6e- + 6H+ + ClO3- --> Cl- + 3H2O
    Br2 + 6H2O --> 2BrO3- + 12H+ + 10e-
    5. Add up equations (need to multiply to balance electrons):
    10[6e- + 6H+ + ClO3- --> Cl- + 3H2O] =
    6[Br2 + 6H2O --> 2BrO3- + 12H+ + 10e-] =

    60e- + 60H+ + 10ClO3- --> 10Cl- + 30H2O
    6Br2 + 36H2O --> 12BrO3- + 72H+ + 60e-
    -----------------------------------------
    6Br2 + 10ClO3- + 6H2O --> 12BrO3- + 10Cl- + 12H+

    Add up the electrons exchanged in the reaciton and there's your answer (the last step of adding the equation wasn't really necessary to solve your problem). Hope you understand what I did.
     
  4. Oct 27, 2005 #3

    Borek

    User Avatar

    Staff: Mentor

    Cesium: your final equation should be divided by 2 :)

    This equation can be balanced without redox approach.
     
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