Saturated solution of KNO3 is used to make 'salt bridge' because:
velocity of K+ is greater than that of NO-3
velocity of NO-3 is greather than of K+
velocity of both NO-3 and K+ are nearly same
KNO3 is highly soluble in water
As we have learnt,
Function of Salt Bridge and Condition -
It maintains electrical neutrality in two compartments by allowing movement of anions towards anodic compartment and cations towards cathodic compartment.
-
The salt bridge possesses the electrolyte having nearly same ionic mobilities of its cation and anion.
Therefore, Option(3) is correct