[Georgia74753]

Hi, in class we electrolysed concentrated KI and we had to deduce the products at each electrode. At the anode it was I₂ (tested with starch) and at the cathode it was H₂ (tested with a lighted match).

So the half equations were:
2I^-  I₂ + 2e^-
2H₂O + 2e^-  H₂ + 2OH^-

Now we have to work out:
a) What the products at the anode and cathode would be if dilute KI was electrolysed
b) Why potassium wasn't produced
c) How could the experiment could be changed to produce potassium?

For a) I think that the anode product would be O₂ and the cathode product would still be H₂ because of past practicals we have done. If somebody could please explain this to me or correct me that would be great.

I'm not really sure about b). Is it something to do with reactivities and which reacts first?
And I'm really stuck on c)

Any help ASAP would be really appreciated, thanks!

[rosa]

  Hallow Moderator,
Suggestions on your questions are:
For (a) You need to recall factors that affect selective discharge of electrolytes. The concentrations of the ions in solution will dictate which ions are to be preferentially discharged. Besides concentration, the reactivity of the ion also need to be considered.
(b) Compare the reducing strength of Potassium and that of Hydrogen.The weaker one will be oxidised fisrt.
(c) The type of electrolyte can help dictate the products at the electrodes. A binary electrolyte gives only two distinctive results. How about obtaining a binary electrolyte from Potassium Iodide