Electrode potential is the tendency of a metal electrode to lose or gain electrons when placed in contact with a solution of its own ions, measured relative to the standard hydrogen electrode (SHE).
Every electrochemical cell — from a simple Daniell cell to a battery — works because two electrodes have different electrode potentials. The bigger that difference, the more voltage the cell produces. JEE and NEET questions test this through cell notation, EMF calculation, and predicting which metal gets oxidised versus reduced.
| Standard (E°) | Non-standard (E) |
|---|---|
| 1 M concentration, 298 K, 1 atm | Any real concentration / temperature |
| Fixed, tabulated value | Calculated via the Nernst equation |
| Used to compare metals' reactivity | Used for actual cell EMF in practice |
Exam questions on electrode potential almost always reduce to one skill: given the standard potentials of two half-cells, work out the cell's EMF and decide which electrode is the cathode. The rule to memorise is E°cell = E°cathode − E°anode, where the electrode with the higher (more positive) potential is the cathode. Get that one relationship right and most electrochemistry MCQs fall open.