Question

Select the correct statement
$A)$ $KCl$ can not be used as an electrolyte in a salt bridge in the case of the silver electrode.
$B)$ cell reaction is spontaneous if emf is positive.
$C)$ If the salt bridge is removed, the potential falls to zero.
$D)$ All of these.

Answer 1

The purpose of the salt bridge is not move electrons from the electrolyte, rather to keep up charge balance on the ground that the electrons are moving from one half of the cell to another.

Complete step by step answer:
Let’s see if the given statements are correct or not.
Statement $A)$ is correct.
Because KCl will react with silver and form silver chloride which is insoluble in water.
Statement $B)$ is correct.
As we know, the reaction equation is
$\Delta G = - nF{E^ \circ }$
Here $\Delta G$ is Gibbs free energy and tells us if the given reaction is spontaneous or not. If $\Delta G$ is negative then the reaction will be spontaneous and if $\Delta G$ is positive the given reaction will be nonspontaneous.
Here $n$ is electron exchange and $F$ is Faraday's constant.
So, if the ${E^ \circ }$ is positive then the $\Delta G$ will be negative so the reaction will be spontaneous.
Statement $C)$ is also correct.
Salt bridge allows the flow of current by completing the circuit. No current will stream and the voltage will drop to zero if the salt bridge is eliminated.
all the given statements are correct.

So, the answer is $D)$.

Note:
Reactions that occur spontaneously have a negative $\Delta G$ value, and such reactions are exergonic. The net charge will be zero when the system is at equilibrium because no net change occurs.