A salt bridge is a component of an electrochemical cell, such as the Daniell cell, that connects the two half-cells while preventing direct mixing of their electrolytes. It typically consists of an inverted U-shaped tube filled with a gel or a solution containing an inert electrolyte, such as potassium chloride (KCl).

The salt bridge serves two primary functions in an electrochemical cell:

Ionic Conduction: The salt bridge allows the flow of ions between the two half-cells, completing the circuit for the flow of electrons. As the oxidation and reduction reactions occur in the half-cells, ions are consumed or produced, creating an imbalance of charge. The salt bridge helps maintain electrical neutrality by allowing ions to migrate from one half-cell to the other, preventing the accumulation of excess charge and enabling a continuous flow of current.

Maintaining Electrolyte Balance: The salt bridge helps maintain the ionic balance and concentration in the half-cells. As the reactions progress, the concentrations of the electrolyte solutions in the half-cells can change due to the consumption or production of ions. The salt bridge provides a pathway for the migration of ions, ensuring that the electrolyte concentrations in the half-cells remain relatively stable. This stability helps maintain consistent reaction rates and prevents the depletion of ions that are necessary for the electrochemical reactions to occur.

In summary, the salt bridge facilitates ionic conduction and helps maintain the balance of electrolytes in the two half-cells of an electrochemical cell, ensuring the smooth operation of the cell and the continuity of electron flow.