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Now I know that the anode in a car battery is lead, the cathode is lead dioxide and the electrolyte is sulfuric acid, but still: how could a potassium iodide solution be used to differentiate between the anode and the cathode?

I mean, lead can't replace potassium in its salt because it lies below it in E.C.S., so how are we supposed to identify them by using potassium iodide?

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  • $\begingroup$ Surely you can't replace potassium, but maybe iodine would respond to electric current in some way? Also, welcome to Chem.SE. $\endgroup$ – Ivan Neretin May 3 '17 at 10:11
  • $\begingroup$ Thanks for your help....and it's a pleasue to be a part of this site :) $\endgroup$ – marawan hassan May 3 '17 at 17:16
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By using the battery as a source of electricity in an electrolytic cell that contains potassium iodide as an electrolyte. Electrolysis takes place where iodide ion is oxidized at anode and brown colour of iodine solution appears at anode. At cathode hydrogen gas evolves which is indicated by formation of bubbles at cathode.

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  • $\begingroup$ Given the conditions, iodine is by no means violet, nor is it a gas. Also, potassium would never precipitate from water solution. Other than that, you are right. $\endgroup$ – Ivan Neretin May 3 '17 at 17:23
  • $\begingroup$ But won't iodide ion lose an electron at the anode and iodine will evolve as a gas at the anode and the opposite happens for potassium? $\endgroup$ – user44750 May 3 '17 at 17:26
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    $\begingroup$ You ask too many questions at once. In short, the answers are: yes, no, no. "Yes" means that iodide would indeed lose an electron. $\endgroup$ – Ivan Neretin May 3 '17 at 17:28
  • $\begingroup$ What about the"no,no" ? $\endgroup$ – marawan hassan May 3 '17 at 17:31
  • $\begingroup$ @marawanhassan No, iodine would not evolve as a gas. And no, potassium would not evolve at all. $\endgroup$ – Ivan Neretin May 3 '17 at 19:52

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