3
$\begingroup$

In lecture I was taught that, in a galvanic cell at standard conditions, platinum is often used as an inert electrode when the species being oxidized or reduced exists only in solution, because platinum is "inert," which means it is very stable at and resists reduction or oxidation. This concept confuses me for two reasons:

  1. Reduction means to lose charge, a.k.a. gain an electron(s). When the electrode has an electron passing through it in order to be transferred to another material, isn't it being reduced, albeit for a very miniscule amount of time? So, if we were to pause the cell during electron transfer and examine the iron wire and platinum electrode, we'd see a charge of -1 on both of them, correct?

  2. I Googled the SRP of platinum, and this link states that $\ce{Pt^2+ -> Pt}$ has an SRP of $\pu{1.2 V}$. This translates to an "oxidation" potential of $\pu{-1.2 V}$. This one confuses me because, if we were to use a platinum electrode during the oxidation of $\ce{Mn^3+ +e^--> Mn^2+}$, which has an SRP of $\pu{1.54 V}$ (An "oxidation" potential of $\pu{-1.54 V}$), wouldn't the platinum electrode be the one to oxidize, as it has the higher value?

One concept that I'd like to imagine is that inertness is more about a lack of change in properties of the element as it reduces or oxidizes rather than it is about the "inability" to oxidize or reduce. This still doesn't explain how platinum can function as an electrode for species with a lesser standard reduction potential, though.

$\endgroup$
7
  • 4
    $\begingroup$ There is no way to oxidize fluoride in water solution. Water gets oxidized to O2 instead. $\endgroup$ – Poutnik Apr 3 at 12:27
  • 3
    $\begingroup$ Hint: what is the electrochemical window in your reaction medium, i.e. what electrochemical potentials are experimentally accessible without destroying your electrolyte? $\endgroup$ – Buttonwood Apr 3 at 12:30
  • 5
    $\begingroup$ Keep in mind that a redox potential is thermodynamic quantity. It does not say if related reactions go fast, slow or without noticeable change at all. $\endgroup$ – Poutnik Apr 3 at 16:09
  • 1
    $\begingroup$ Upon all, the inertness is a relative term here. $\endgroup$ – Mathew Mahindaratne Apr 3 at 19:14
  • 1
    $\begingroup$ $\ce{Mn^3+ + e- -> Mn^2+}$, $E^\circ = \pu{1.54 V}$. $\endgroup$ – Mathew Mahindaratne Apr 3 at 19:28

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.