Question on chemical cells yet again? Thanks!?

Question

On the electrochemical series, using a more reactive metal at the top of the series, e.g. magnesium, and also a less reactive metal at the bottom of the series, e.g. copper, will create a larger current than using zinc and iron together. The larger the distance on the series between two metals, the larger the current they produce.

This means that if we use potassium and silver together, an even larger current will be generated. But why do people don't use this couple in cells? Besides potassium being expensive and also easily oxidized, are there any other reasons for not using this couple?

Will the current over discharge drop rapidly if we use potassium and silver together? Thanks!

Answer 1

What you haven't realised with reference to a potassium electrode is that (a) it is the voltage difference which becomes larger as the distance between the two metals in the reactivity series increases, and not necessarily the current and (b) a potassium electrode (or any metal electrode) needs to be in equilibrium with its aqueous ions. The practical difficulties of having a piece of potassium dipped into a solution of potassium chloride without exploding are enormous!