Question

Assertion: In electrochemical cell, we cannot use $KCl$ in the salt bridge if anodic or cathodic compartment consists of $A{{g}^{+}}$ or $P{{b}^{2+}}$ ion.
Reason: Salt Bridge is employed to maintain the electrical neutrality and to minimize the liquid-liquid junction potential.
(a)- Both assertion and reason are correct and the reason is the correct explanation for the assertion.
(b)- Both assertion and reason are correct and the reason is not the correct explanation for the assertion.
(c)- Assertion is correct but the reason is incorrect.
(d)- Assertion is incorrect but the reason is correct.

Answer 1

Hint: $A{{g}^{+}}$ or $P{{b}^{2+}}$ ion readily react with chloride ions to for$AgCl$ or $PbC{{l}_{2}}$ precipitate. 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.
But if the anodic or cathodic compartment has silver ions or lead ions, the $KCl$ in the salt bridge will react with these ions and form $AgCl$ and $PbC{{l}_{2}}$ precipitate which will stop the function of the galvanic cell. That’s why we don’t use $KCl$ in the salt bridge.
The reason mentioned from the above discussed is correct but it is not the correct explanation for the given reason.

Therefore, the correct answer is an option (b)- Both assertion and reason are correct and the reason is not the correct explanation for the assertion.

Note: If the correct electrolytes in the salt bridge 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.