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In an electrochemical cell, electrons flow from negative electrode to the positive electrode. This shows that there is a potential difference between the two electrodes.
The minimum potential which causes the flow of the electrons from the negative electrode to the positive electrode is called emf.
The emf of a cell is defined as the algebraic difference between the SRP of the positive electrode and the SRP of the negative electrode even though oxidation is taking place at the negative electrode.
| Standard reduction potential of cathode | Standard reduction potential of anode |
|---|---|
| Eo Cathode | Eo Anode |
| or | |
| E Right | E Left |
In general, for a given electrode, the magnitude of oxidation and reduction potentials remain same but they differ with respect to their signs.
Example:
For a cell made of a zinc electrode in ZnSO4 and copper electrode in CuSO4,
= 0.35 - (-0.76)
= 1.1 V
