galvanic

Meaning: A galvanic (voltaic) cell converts a spontaneous redox reaction into electrical work. The two half-reactions occur in separate compartments joined by a wire and a salt bridge. Oxidation occurs at the anode, reduction at the cathode, and electrons travel through the wire from anode to cathode. In a galvanic cell the anode is the negative electrode and the cathode is positive. The salt bridge lets ions migrate so each half-cell stays neutral: anions move toward the anode, cations toward the cathode.

Equation: ΔG° = −nFE°cell, with E°cell = E°cathode − E°anode. Here n is moles of electrons transferred (mol), F is the Faraday constant, 96,485 C/mol, E is in volts (V), and ΔG° is in J per mole of reaction.

On the MCAT: A table of standard reduction potentials is given. The half-reaction with the more positive E° is the cathode. Subtract to get E°cell, then predict electron flow, which electrode gains mass (plating at the cathode) or loses it (a metal anode dissolving), and salt bridge ion movement. The Nernst equation predicts how concentration changes shift E, and the cell potential falls to zero at equilibrium.

Common confusion: Electrode signs flip in an electrolytic cell, where the anode is positive. Oxidation still occurs at the anode and reduction at the cathode in both cell types. A positive E°cell means spontaneous as written.