September 16, 2019, 08:40:41 PM
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Topic: Do following half-reactions have ph-dependent electrode potential?  (Read 213 times)

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Offline dolphinsea14

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Do following half-reactions have ph-dependent electrode potential?
« on: September 01, 2019, 08:16:54 PM »
Do following half-reactions have electrode potential that depends on pH? I know H+ or OH- ions wouldn't be included in Nernst equation for these, but would pH affect chemical balance in these reactions, and therefore electrode potentials?
Br2+2e- :rarrow: 2Br-
Cl2+2e- :rarrow: 2Cl-
I2+2e- :rarrow: 2I-
S2O8+2e- :rarrow: 2SO42-

Offline Borek

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Re: Do following half-reactions have ph-dependent electrode potential?
« Reply #1 on: September 02, 2019, 03:28:18 AM »
Can you think of any side reactions involving mentioned substances and pH dependent?
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Offline dolphinsea14

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Re: Do following half-reactions have ph-dependent electrode potential?
« Reply #2 on: September 03, 2019, 07:31:45 PM »
I'm not sure, that's why I ask. Can side reactions affect electrode potential? Wouldn't they just shift equilibrium, and wouldn't equilibrium constant in Nernst equation remain the same value as before?

Offline Borek

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Re: Do following half-reactions have ph-dependent electrode potential?
« Reply #3 on: September 04, 2019, 02:56:27 AM »
I'm not sure, that's why I ask. Can side reactions affect electrode potential? Wouldn't they just shift equilibrium, and wouldn't equilibrium constant in Nernst equation remain the same value as before?

Constant remains the same, but what if shifting the equilibrium by a side reaction changes concentrations of an ion involved in the redox process?
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Offline dolphinsea14

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Re: Do following half-reactions have ph-dependent electrode potential?
« Reply #4 on: September 04, 2019, 08:06:12 AM »
I found this in a book (Inorganic Chemistry by Shriver and Atkins). It seems redox potential in these cases doesn't depend on pH.

Offline Vidya

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Re: Do following half-reactions have ph-dependent electrode potential?
« Reply #5 on: September 06, 2019, 01:49:27 AM »
You need to check the ions involved ..if they are conjugate bases of  strong acid then they will not get hydrolyzed in water like Cl- Br- and I- are weak conjugate  bases of strong acids HCl,HBr and HI.
However conjugate bases of weak acids are hydrolyzed in water and releases OH- which makes it pH sensitive.


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