[confusedstud]

For anions the higher  concentration of the halide ions will result in the selective discharge if them. However, for cations I read that the concentration of cations close to each other in the reactivity series will be affected by concentration. how far can they be from each other? For example, iron, lead, hydrogen, copper mercury. I understand that lead will be affected by concentration but will iron be affected? Also, will copper and mercury be affected?

Lastly, what concentration of the compounds then it will have the selective discharge effect?  if a question simply asks "what is the product of electrolysing a lead nitrate solution with inert electrodes"