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Predicting the anode product in electrolysis


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#1 Manusha Ramanayake

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Posted 2 November 2016 - 02:22 AM

Hello,

 

I'm just doing some electrolysis experiments

In electrolysis it is easy to predict the cathode products resulting from an electrolyte but not the anode product.

If a electrolyte contains many anions, is there any way to predict the anode product before the experiment.

For example if a electrolyte have OH-(aq) , Cl-(aq) , I-(aq) what gas will form near the anode.   


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#2 John Cuthber

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Posted 2 November 2016 - 07:46 PM

"is there any way to predict the anode product before the experiment."

Yes

https://en.wikipedia...Nernst_equation

and

https://en.wikipedia...trode_potential

and

http://www.physchem...._potentials.htm

 

and some other bits of stuff too.

It's possible, but not easy.

 

The simple answer is that you get whichever product is easiest to make and that's whichever product (on the left hand side of the eqn)  is furthest up the table in the 3rd link

(so, you practically never get lithium metal and it's much easier to get iodine than chlorine.)


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#3 Manusha Ramanayake

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Posted 3 November 2016 - 01:45 AM

"is there any way to predict the anode product before the experiment."
Yes
https://en.wikipedia.org/wiki/Nernst_equation
and
https://en.wikipedia.org/wiki/Standard_electrode_potential
and
http://www.physchem.co.za/data/electrode_potentials.htm
 
and some other bits of stuff too.
It's possible, but not easy.
 
The simple answer is that you get whichever product is easiest to make and that's whichever product (on the left hand side of the eqn)  is furthest up the table in the 3rd link
(so, you practically never get lithium metal and it's much easier to get iodine than chlorine.)



Thank you for the quick reply
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#4 Sriman Dutta

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Posted 10 December 2016 - 08:29 AM

The electrochemical series of anions will help you- the lower anions are discharged in preference to the higher anions in the series. This is called selective discharge of ions. 


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