Electrochemistry Reference Electrodes

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Discussion Overview

The discussion revolves around converting electric potential readings from an Ag/AgCl reference electrode system to a reversible hydrogen electrode (RHE) system at pH 7. The context is primarily homework-related, focusing on the calculations and assumptions involved in this conversion.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant presents a calculation for converting potentials from Ag/AgCl to RHE, initially stating RHE at pH 7 as 0.4137 V.
  • Another participant challenges the calculation, noting that -0.0591 multiplied by 7 does not yield 0.4137 V and suggests inconsistencies in the signs used.
  • A subsequent reply corrects the sign for RHE at pH 7 to -0.4137 V, indicating that the initial assumption of the sign was incorrect.
  • A question is raised about the value 0.197 V used in the calculations, prompting clarification on its relevance compared to the earlier mentioned 0.222 V.
  • The original poster acknowledges the confusion regarding the values, clarifying that 0.222 V is the correct reference for the Ag/AgCl system, while 0.197 V pertains to a different context.

Areas of Agreement / Disagreement

Participants express uncertainty regarding the signs and values used in the calculations, leading to a lack of consensus on the correct approach. There is no clear agreement on the final values or the reasoning behind them.

Contextual Notes

There are unresolved issues regarding the assumptions made about the signs in the calculations and the relevance of the different reference voltages mentioned (0.197 V vs. 0.222 V). The discussion does not clarify the implications of these differences.

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Homework Statement



Change your electric potential readings from a Ag/AgCl system to a RHE (reversible hydrogen electrode) system at pH 7.

For example, 0.3 V vs Ag/AgCl and -0.1 V vs Ag/AgCl

Homework Equations



Ag/AgCl 0.222 Volts
RHE 0 - 0.0591*pH Volts

The Attempt at a Solution



RHE at pH 7 = 0.4137 V

0.3 V vs Ag/AgCl + (0.197 - 0.4137) = 0.08333 V ?
-0.1 V vs Ag/AgCl + (0.197 - 0.4137) = -0.3167 V ?
 
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-0.0591*7 is not 0.4137

Not that I am sure about the correct signs, but what you did looks inconsistent.
 
ah yes I forgot to put that negative sign on my post. So RHE at pH 7 = 0.4137 V should really be read as RHE at pH 7 = -0.4137 V
everything below that assumed that sign was there in the first place.

Are my signs or thinking inconsistent? I was trying to think of everything in terms of SHE (standard hydrogen electrode), which is marked as 0 V.
 
What is 0.197?

Edit: I mean, I know what it is, I wonder why you used 0.197 on calculations, but you listed 0.222 earlier.
 
I was given 0.222 V.
0.197 V would be for a saturated chloride solution, ooh, oups, that belongs to a followup problem (not relevant to this thread), I see what you mean now. It should say 0.222 V not 0.197 V
 

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