What is a Liquid/Liquid Junction Potential and Its Role in Batteries?

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Discussion Overview

The discussion revolves around the concept of liquid/liquid junction potential, specifically whether such a potential exists between two liquids of the same composition but different concentrations in the absence of an external electrical circuit and electrodes. The conversation explores theoretical implications and comparisons to other phenomena in electrochemistry and thermoelectric devices.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions the existence of a liquid/liquid junction potential without an external circuit or electrodes, suggesting that if it is not measurable, its existence is uncertain.
  • Another participant asserts that the potential exists because the solutions are conductors, indicating that it is typically measurable.
  • A subsequent reply challenges the relevance of provided links that involve electrodes and RedOx reactions, emphasizing the original question's context.
  • One participant references theoretical sources that suggest the potential may exist even if it cannot be directly measured.
  • Another participant agrees that the mechanism implies the existence of the potential, regardless of measurement capability.
  • A comparison is drawn to similar phenomena at metal-metal conductor junctions, noting that while not strictly necessary for thermocouples, it is often utilized.
  • One participant relates the discussion to batteries, stating that they have an internal EMF even when not connected, and describes the resulting electric field as an electroneutrality field that maintains charge separation.

Areas of Agreement / Disagreement

Participants express differing views on the existence and measurability of liquid/liquid junction potential, with no consensus reached on the matter. Some agree that it exists theoretically, while others question the implications of non-measurability.

Contextual Notes

Limitations include the dependence on the definitions of potential and measurability, as well as the unresolved nature of the discussion regarding the implications of non-detectability.

somasimple
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Liquid junction potential question
Hi,
Is there a liquid/liquid junction potential between two liquids of same composition but different concentrations WHEN there is no external electrical circuit and then NO electrodes? (Of course this potential is not measurable).

Thanks,
 
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Well, the links you gave show electrodes then there is a RedOx reaction with charge transfer within the external circuit. That is not my question.
 
somasimple said:
Summary:: Liquid junction potential question

Of course this potential is not measurable
If something is not detectable, then how would anyone know?
 
Yes, from the mechanism it exists even without being measured.
 
Thanks for this reply.
 
Thanks again Atyy,
The same phenomenon applies to batteries. They have an internal EMF even if they are not connected but one can not know their inner potential without connecting them. The charge separation creates an Electric field also called an electroneutrality field. It is the force that let's the things in place.
 

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