Question

give reason for the variation of value of single electrode potential of calomel electrode with respect to concentration of kcl.

Answer 1

The reason as to why the variation of single electrode potential colomel electrode with respect to concentration of potassium chloride  is that KCl acts as a reservoir of chloride ions hence when its concentration is low it means that chloride ions ions are low and when its high it means that the concentration of chloride ions is high.

KCl also act as either anode or cathode. Ad it can also act as a salt bridge.