Products of Electrolysis (1 Viewer)

[wrxsti]

How do we determine the product of electrolysis?
Like does the Chemical which has the highest reduction potential get reduced?

eg) Electrolysis concentrated of NaCl

Anode-Oxidation 2Cl- -> Cl2 + 2e-
Cathode-Reduction .
For this cathodic reaction.. involving H20 would it be the H20 reaction with the HIGHEST reduction potential ? so

2H20 + 2e- -> H2 + 2OH- ??

or would it be the one which is closest to zero (ie, least voltage neeeded)
?

 

[brenton1987]

I work it out by writing out all the possible reactions

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2Cl^- --> Cl₂ + 2e^- (-1.36V)
2H₂O --> O₂ + 4H⁺ + 4e^- (-1.23V)

H₂O + 2e^- --> H₂ + 2OH^- (-0.83V)
Na⁺ + e^- --> Na (-2.71V)

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The reactions that occur are going to depend on the voltage passes through the solution. In theory the water should oxidise and reduce but at >3V the overvoltage prevents the water from oxidising.

The reactions you get are
2Cl^- --> Cl₂ + 2e^- (-1.36V)
H₂O + 2e^- --> H₂ + 2OH^- (-0.83V)

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I have a feeling that that was unnecessarily complicated.