What role does a salt bridge play in an electrochemical cell, and what would happen if it were removed?

• A. The salt bridge conducts electrons.
• B. The salt bridge maintains electrical neutrality by migrating ions to balance charge as electrons flow; without it, charge would accumulate, rapidly halting the cell.
• C. It increases the reaction rate.
• D. It serves as a reference electrode.

Answer: (B)

The key idea is that the salt bridge keeps the two half-cells electrically neutral as the redox reaction proceeds. As electrons flow through the external wire from the anode to the cathode, the anode side tends to accumulate positive charge (from metal ions entering solution or from oxidation), while the cathode side can accumulate excess negative charge as reduction removes ions from solution. The salt bridge provides a path for ions to migrate: anions move toward the anode compartment to balance positive charge, and cations move toward the cathode to balance negative charge. This ion flow prevents charge buildup, allowing continuous electron flow and sustained current. If the salt bridge were removed, charge would accumulate in each half-cell, the internal resistance would rise quickly, and the cell would stop functioning almost immediately. The salt bridge doesn’t transport electrons itself, and it isn’t a reference electrode, nor does it directly speed up the chemical reactions.