May 28, 2023, 01:48:01 PM
Forum Rules: Read This Before Posting


Topic: Electrolysis of Water in a divided cell: What happens to the hydroxide ions?  (Read 2666 times)

0 Members and 1 Guest are viewing this topic.

Offline Zensation

  • Regular Member
  • ***
  • Posts: 56
  • Mole Snacks: +1/-1
In such a situation, in the catholyte, what happens to the hydroxide ions?

Say you were doing electrolysis on water to collect H2 only from the divided cell. Water would be split at the cathode :
2 H2O(l) + 2eāˆ’ ā†’ H2(g) + 2 OH-(aq)

On wikipedia it says the OH-anions would gravitate to the anode to merge with the H+ cations that are formed... but what if they can't get over there.

Do the OH- anions just continually build up in the cell? Are these unstable in their current forms, and likely to react? For some reason I imagine O2 and H2 to be formed if two of these react, but I have an inkling that is not correct, as there is no mention of it anywhere.


I have seen in situations of electrocatalytic reductions in a divided cell that the organic material is extracted out and then acidified to a salt form, and many of these papers make no mention of how the hydroxide anions would act as a base and neutralize any acid before any acid can react with the organic molecule. Which would imply that the Hydroxide anions are not existing at that stage of the extraction. What happens to them?


Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27354
  • Mole Snacks: +1775/-408
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
If you can somehow stop transfer of the ions, a counterpotential will build up pretty soon and the electrolysis will stop.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Offline Zensation

  • Regular Member
  • ***
  • Posts: 56
  • Mole Snacks: +1/-1
When you say stop the transfer of ions... are you implying that hydroxide anions will travel through the salt-bridge of the divided cell? I'm honestly asking because I have no clue. Is this possible? I thought a salt-bridge would merely act to transfer the electrons.


Online Borek

  • Mr. pH
  • Administrator
  • Deity Member
  • *
  • Posts: 27354
  • Mole Snacks: +1775/-408
  • Gender: Male
  • I am known to be occasionally wrong.
    • Chembuddy
Salt bridge doesn't transfer electrons - it transfers charge allowing ions to move.
ChemBuddy chemical calculators - stoichiometry, pH, concentration, buffer preparation, titrations.info, pH-meter.info

Sponsored Links