Arun
Last Activity: 6 Years ago
Applications of electrode potential:
- relative strengths of oxidizing and reducing agents
- thermodynamic cell potential
- unknown concentration
- pH
- free energy (G)
- equilibrium constant
- solubility products
- dissociation constant
- titration curve
First, ask yourself what an electrode is: that is, the means by which substances are included in electrical circuits it may be a metal or solid substance (mixture) and the characteristics depend on the metal or solid and the solution in which it is put in.
Second, ask yourself what an electrode potential is: that is, an electromotive force (aka cell potential) of a cell that has two electrodes.
Dependence of electrode potential:
- Concentration
- Temperature
- Pressure (in gaseous reactions only)
Electrode potential can never be measured directly it can only be measured by comparing an electrode with a standard or reference electrode. Essentially, an electrode potential is the voltage that an electrode is at, this has to measured versus a reference electrode. So what electrochemical cell are we using?
- Voltaic (Galvanic) Cell
- Electrolytic Cell
The electrical potential difference is set up between the metal and its solution. Also, half cell reactions have their individual electrode potential because two different types of reactions take place on them:
For example, Cu -AgNO3 the reactions will proceed as follows:
Oxidation half reaction: (electrode) Cu (s) ⇌ (solution) Cu2+ + (on electrode) 2e-
Reduction half reaction: 2Ag+ + 2e- ⇌ 2Ag
Overall cell reaction: Cu + 2Ag+ ⇌ Cu2+ + 2Ag
The cell may be represented as:
Cu(s) I Cu2+ (aq) II Ag+(aq) I Ag(s)
However, there is more to this, the double electrical layer. That is, the decomposition of negative charges on the electrode when the chemical potential of copper ions in the metal is less than chemical potential of the copper ions in solution then at the dipping of electrodes some quantity of the copper ions are hydrated and transferred to the metal which forms a positive charge on the metal surface.