Galvanic cell EMF
MCAT glossary · Chemical & Physical Foundations of Biological Systems
Definition
E°cell = E^circcathode - E^circanode; ΔG° = -nFE°; spontaneous when E°cell > 0.
Galvanic cell EMF in plain English
A galvanic cell is basically a battery: two metals sitting in solution, wired together, where a chemical reaction pushes electrons through the wire and does useful work (like powering a flashlight). The EMF, written E°_cell, is the 'push' or voltage the cell can generate, and you find it by subtracting: E°_cell = E°_cathode − E°_anode, where the cathode is where electrons arrive and the anode is where they leave. The key rule: if E°_cell comes out positive, the reaction happens on its own (spontaneous) — a positive push means the battery wants to run. The formula Δ G° = −nFE° just translates that voltage into energy language (n is electrons transferred, F is a constant), and because of the minus sign, positive voltage always means negative Δ G°, which is the official signature of a spontaneous reaction.
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