Voltaic (Galvanic) Cell
Voltaic vs Electrolytic
| Voltaic | Electrolytic | |
|---|---|---|
| Energy | Chemical → Electrical | Electrical → Chemical |
| Spontaneous? | Yes (ΔG < 0) | No (ΔG > 0) |
| Anode | Negative (−) | Positive (+) |
| Cathode | Positive (+) | Negative (−) |
In BOTH types: oxidation at anode, reduction at cathode (An Ox, Red Cat).
Standard Electrode Potential E° (HL)
\( E°_{cell} = E°_{cathode} - E°_{anode} \)
If E°cell > 0, the reaction is spontaneous (voltaic cell works).
Think About It
Why does the salt bridge contain ions like KNO₃ rather than reactive metal ions?
K⁺ and NO₃⁻ are spectator ions — they don't participate in redox reactions. The salt bridge completes the circuit by allowing ion flow to maintain electrical neutrality in each beaker, without interfering with the cell reaction.