Question

$KCl$ is used in the salt bridge because:
(a)- It forms a good jelly with agar-agar
(b)- It is a strong electrolyte
(c)- It is a good conductor of electricity
(d)- The transfer number of ${{K}^{+}}$ and $C{{l}^{-}}$ ions are almost equal

Answer 1

The main function of the salt bridge in the galvanic cell is the transfer of cations and anions in the solution. This is an important part of the galvanic cell because it maintains electrical neutrality.

Complete step by step answer:
Let us study the salt bridge and its function:
A U-shaped tube containing a concentrated solution of an inert electrolyte like $KCl,\text{ }KN{{O}_{3}},\text{ }{{K}_{2}}S{{O}_{4}}$, etc, or a solidified solution of such an electrolyte in agar-agar and gelatin is known as a salt bridge. These electrolytes are inert electrolytes whose ions do not take part in the redox reaction and they do not react with other electrolytes used.
So, the main function of the salt bridge is to allow the movement of the ions of one solution to the other solution without mixing both the solutions. The electrons flow in the outer circuit, whereas the flow of electrons in the inner circuit is completed by the flow of ions through the salt bridge, hence it is necessary for maintaining the electrical neutrality of the solution in the galvanic cell.
So, the electrolytes used are those which form an equal number of ions in the solution.

So the correct answer is an option (d)- The transfer number of ${{K}^{+}}$ and $C{{l}^{-}}$ ions are almost equal.

Note: If the electrolytes are not used then the electrolytes in the electrode will move and start to accumulate, thereby stopping the flow of further electrons, this, in turn, will stop the working of a galvanic cell.