Electrode potential and its applications

Prepared by
Saba Shahzadi
Course Coordinator
Dr. Shahnaz Rashid

Topics to be learned….
 Electrode Potential (definition)
 Introduction to Electrochemistry
 Electrochemical cells
 Electrodes
 Electrode potential
 Concept of electrode potential
 Half cell reactions
 Types of electrode potentials
 Cell Potential or E.M.F and its difference from Potential
Difference
 Dependence of Electrode Potential
 Measurement of Electrode Potential
 Electrochemical Series
 Applications of Electrode Potential

Electrode Potential
 Electrode potential is the voltage that an electrode is
at , this has to measured versus a reference electrode.
 Electrode potential is electromotive force of a cell that
has two electrodes.

Introduction to Electrochemistry
Electrochemistry is a branch of chemistry which involves
the interconversion of electrical and chemical energy.
 These conversions are carried out through
electrochemical cells.

Electrochemical Cells
There are two main types of electrochemical cells
 Voltaic or Galvanic Cell
 Electrolytic Cell
The concept of electrode potentials could be understand
by the composition of any one of the above.

Construction of Electrochemical
cell

What are Electrodes?
 Electrodes are the means by which liquid and living
organisms are included in electrical circuits.
 There are two electrodes in each electrochemical cell.
 It may be a metal or a solid substance (mixture)
 Its characteristics depend on the metal or solid and the
solution in which it is dipped.

Electrode Potential
 The electrical potential difference set up between the
metal and its solution is known as electrode potential.

Half Cell Reactions
 Both of the half cells have their own individual
electrode potential because two different type of
reaction take place on them.
 At anode
oxidation reaction occurs.
At cathode
reduction reaction occurs.
Zn+2 + 2e- Zn

Concept of Electrode Potential
Double layer Formation:
The deposition of negative charges on the
electrode when the chemical potential of copper’s ions
in the metal is less than the 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 metal surface.
These processes cause the double electrical layer.

Double Layer
1- metal
2 - solution

Types of electrode potential
 Oxidation Potential
 Reduction potential
 Standard cell potential
(standard hydrogen electrode)
 Cell potential

Cell Potential and its difference
from potential difference
The difference between the electrode
potentials of the two electrodes constituting
an electrochemical cell is known as
electromotive force (e.m.f.) or cell potential of a cell.

Dependence of Electrode Potential
 Concentration
 Temperature
 Pressure
(in case of gases only)

Measurement of Electrode
potential
 Electrode potential can never b measured directly it
can only be measured by
Comparing an electrode with a standard or reference
electrode.
These electrodes may be S.H.E or calomel electrode.

Applications of electrode Potential
Determination of
 Relative strengths of oxidizing and reducing agents.
 Thermodynamic cell potential
 Unknown concentration
 pH
 Free energy
 Equilibrium constant
 Solubility products
 Dissociation constant
 Titration curve

Continued…
Predict the
 Direction of electron flow
 Feasibility of the reaction
 Weather a metal can liberate hydrogen from acid or
not

Electrode potential and its applications

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