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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: bear_007 on August 03, 2020, 11:55:02 AM

Title: Electrolysis of potassium iodide
Post by: bear_007 on August 03, 2020, 11:55:02 AM

Iodine gas forms at Anode but hydroxyl ion is more reactive in the electrochemical series so it should electrolyse and for, oxygen, I assume if that is what is formed by hydroxyl ion, correct me if I am wrong.

Why iodine and not oxygen?

Title: Re: Electrolysis of potassium iodide
Post by: Borek on August 03, 2020, 06:22:13 PM

Most often it is kinetics, oxygen is notoriously slow and requires overpotential to react faster.

Title: Re: Electrolysis of potassium iodide
Post by: bear_007 on August 06, 2020, 01:42:34 PM

thanks

Title: Re: Electrolysis of potassium iodide
Post by: Enthalpy on August 06, 2020, 02:47:54 PM

I don't quite grasp the "more reactive" argument.

The electrolyte contains mainly K⁺ and I^-. These are the ions attracted by the electrodes. H⁺ and OH^- are rare in a neutral solution.

At the electrodes, other compounds can evolve if the neutralised ions decompose water or combine in some other way. For instance K doesn't remain metallic in water, so you can obtain hydrogen and keep K⁺. But with iodine? I could at most imagine the formation of a hypoiodide. I don't imagine iodine in water forming something like HI and O₂. Or did I get it wrongly?