Standard Electrode Potential

Standard Electrode Potential (E°)

In answering problems involving E°, the following few points should be carefully remembered.

We know that, intensive properties are those whose values do not depend upon the amount of material chosen. Color, physical state, temperature, density etc., are the examples of intensive properties. Like these E° is also an intensive property. Hence in whatever way we write, its value remains same (i.e.,)

Cl₂ + 2e^–  ↔ 2Cl^–       E° = 1.36 volt

Cl₂ + e^– ↔ Cl^–     E° = 1.36 volt

∴ E°_Cl2/2cl^– = E°_{(1/2)Cl2/cl^–}

But ΔG is an extensive property like heat content and mass, because they depend on the amount of material.

If the  combination of two half reactions yields a third half reaction, ΔG of such a reaction is additive, but the potential E° is not additive. E° of such cell indicating such third half reaction can be evaluated from the ΔG value e.g.,

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