In the functions of salt bridge which is incorrect?

It keeps the e.m.f. of the cell positive.

The correct answer is option 3. It keeps the e.m.f. of the cell positive.

Let us analyze each function of a salt bridge in the context of electrochemical cells to determine which statement is incorrect:

1. Allows ions to go from one half-cell to another:

This statement is correct. A salt bridge consists of an electrolyte (typically potassium chloride, KCl) that allows ions to migrate between the two half-cells of an electrochemical cell. This migration is necessary to maintain electrical neutrality and complete the circuit.

2. Provides electrical connection between two half-cells:

This statement is correct. The salt bridge completes the circuit between the two half-cells of an electrochemical cell, allowing the flow of electrons from the oxidation half-reaction to the reduction half-reaction.

3. Keeps the e.m.f. of the cell positive:

This statement is incorrect. The salt bridge does not affect the electromotive force (e.m.f.) of the cell directly. The e.m.f. of the cell is determined by the potential difference between the two half-reactions (oxidation and reduction) occurring in the cell. The salt bridge's primary role is to maintain electrical neutrality and allow ion flow, not to influence the magnitude or sign of the cell's e.m.f.

4. Maintains electrical neutrality of the solution in two half-cells:

This statement is correct. One crucial function of the salt bridge is to maintain electrical neutrality in both half-cells. As electrons flow from one half-cell (where oxidation occurs) to the other half-cell (where reduction occurs), ions move through the salt bridge to balance the charges and prevent buildup of charge that would inhibit further electron flow.

The incorrect statement about the functions of a salt bridge is: (3) It keeps the e.m.f. of the cell positive.

The correct function of a salt bridge does not involve influencing the e.m.f. of the cell but rather facilitating ion flow and maintaining electrical neutrality between the half-cells.