Galvanic cells, electron flow and salt bridges

Galvanic cells, electron flow and salt bridges

A galvanic cell uses a spontaneous redox reaction to produce electrical energy. At the anode, oxidation releases electrons; at the cathode, reduction accepts electrons. Electrons move through the external wire from anode to cathode. Without ionic movement, charge would build up: anions from a salt bridge migrate toward the anode compartment where positive ions are produced, while cations migrate toward the cathode compartment where positive ions are removed. The salt bridge completes the internal circuit but does not supply electrons to the wire. A correct cell diagram labels electrodes, solutions, direction of electrons and ion migration.

Work it through

In a zinc-copper cell, zinc metal oxidises to Zn²⁺ at the anode. Electrons travel to the copper cathode, where Cu²⁺ is reduced to copper metal. As Zn²⁺ accumulates, anions from the salt bridge move into that half-cell. As Cu²⁺ is removed, cations move into the copper half-cell. This preserves electrical neutrality in both solutions.

Mastery target

Explain a galvanic-cell mechanism using anode/cathode half-reactions, external electron flow, salt-bridge ion migration and conservation of charge.