What happens during the electrolysis of concentrated aqueous potassium chloride?

I.     Reduction takes place at the negative electrode (cathode).

II.     Hydrogen gas is evolved at the negative electrode (cathode).

III.     The pH of the electrolyte increases.

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

D

There were four comments on this question, more than the others and, indeed, it was the second most difficult question (just under 46% correct).

This was a tough but fair question. Students have studied the electrolysis of aqueous sodium chloride (19.2.1) so would be expected to transfer that understanding to aqueous potassium chloride. Chlorine gas is produced at the anode but much of this will bubble away as a gas rather than cause acidity to neutralize the hydroxide ions forming around the cathode.