Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Electrochemistry query

  1. Jul 3, 2017 #1

    TJT

    User Avatar

    Hi All,

    I have a quick - probably quite basic - electrochemistry query I hope you can help with...

    I have an anode and a cathode separated by water with current flowing between. There is some oxygen dissolved in the water so the reaction O2 + 2H20 + 4e -> 4OH occurs. Electrons flow out of the anode and into the cathode. At the anode, the electrons are used to convert O2 and H20 to OH (hydroxide). At the cathode electrons are removed to re-form O2 and H2) from the hydroxide?

    My query is what proportion of the electrons are used in the anode/cathode reactions? If all the electrons are used for chemical reactions then is there no current flow?

    Do you get zero current until you have converted all the O2 to OH? Doesn't seem likely to me but I'm sure I am missing something - I haven't done chemistry for a while...

    Also, I know H2O is basically an insulator unless is has ionic substance in it so assume that there is some NaCl in the water and that this doesn't get involved in the reaction...

    Would be grateful for any advice :-)
     
  2. jcsd
  3. Jul 3, 2017 #2

    Borek

    User Avatar

    Staff: Mentor

    Dissolved oxygen is (almost) irrelevant. Typical products of the water electrolysis are oxygen and hydrogen (and they are products of electrode reactions, just google it).
     
  4. Jul 4, 2017 #3

    TJT

    User Avatar

    Thanks for the really helpful advice....

    I am looking at an experiment which definitely has the O2 + 2H20 + 4e -> 4OH reaction occurring but anyhow, my question is also applicable to the 2H20 -> O2 + 4H + 4e reaction. Do all the electrons flowing across the electrode boundary participate in the reduction/oxidation reactions?

    If all then is there no current flowing through the electrolyte occupying the space between the electrodes?

    If not all then how can I calculate the proportion?
     
  5. Jul 4, 2017 #4

    Borek

    User Avatar

    Staff: Mentor

    Yes, that's how they move across the phase boundary.

    Sure there is - electrons go into solution on one electrode and get out of the solution on the other electrode. To do so they have to travel through the solution - that's the current flowing.
     
  6. Jul 4, 2017 #5

    TJT

    User Avatar

    Thanks for the help - it is appreciated
     
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: Electrochemistry query
Loading...