1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Product at anode of the electrolysis of MgBr2

  1. May 6, 2016 #1
    1. The problem statement, all variables and given/known data
    image.jpg
    Why is the product at anode Br2 for MgBr2? Instead of O2?
    2. Relevant equations


    3. The attempt at a solution
    image.jpg


    The EΘ value for the oxidation of OH- is -0.40 V,
    And that of Br- is -1.07V
    And so, shouldn't oxidation of OH- be easier? And hence, O2 is formed at the anode?
     
  2. jcsd
  3. May 6, 2016 #2

    Borek

    User Avatar

    Staff: Mentor

    If memory serves me well, the explanation lies in the kinetics. In general yes, oxygen should be formed. In practice oxygen evolution is quite slow, so you need an overpotential to speed it up, which moves you into the voltages where Br2 is produced. It is the same with brine solutions, where you can easily smell chlorine despite the fact oxygen should evolve first.
     
  4. May 6, 2016 #3
    Woah I see.. How am suppose to know this during the exam ?
    Anyways, thanks. Are there any other exceptions other than brine and MgBr2?
     
  5. May 6, 2016 #4

    Borek

    User Avatar

    Staff: Mentor

    I believe oxygen in general evolves slowly, so whenever it is one of possible products, other things can be produced as well at higher potentials.

    Note: I am not entirely sure about this explanation, take it with a grain of salt.
     
  6. May 6, 2016 #5
    Alright, thanks!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Product at anode of the electrolysis of MgBr2
  1. Anod Katod BLAH (Replies: 2)

Loading...