1. basic concepts of electrochemistry
Electrochemistry:
a science that studies the relationship between electric
and chemical phenomena and the conversion disciplines
between electric and chemical energy
Differences between the ordinary oxidation-reduction
reaction (redox reaction) occurring in solution and in the
electrochemical cell.
2Fe3+ + Sn2+  2Fe2+ + Sn4+

2. To harvest useful energy, the oxidizing and reducing agent has
to be separated physically in two different compartments so
as to make the electron passing through an external circuit
Reaction takes place at
electrode/solution interface
half-reactions:
oxidation / anode reaction:
Sn2+ - 2e-  Sn4+
reduction / cathode reaction:
2Fe3+ + 2e-  2Fe2+

3. Electrochemical apparatus:
chemical  electric:
primary cell (Galvanic cell)
electric  chemical:
electrolytic cell
Electrode: anode, cathode
positive electrode; negative electrode

4. Nomenclature
• “Redox” Chemistry: Reduction and Oxidation
• Oxidation: Loss of electrons
• Reduction: Gain of electrons
(a reduction in oxidation number)
LEO goes GER
Loss of Electrons is Oxidation
Gain of Electrons is Reduction

5. Reduction form – electrons = oxidized form
The sum of two half – reactions constitutes the redox
reaction, e.g. the oxidation of ferrous ion by ceric ion:
Fe2+ – e = Fe3+ (oxidation half – reaction)
Ce4+ + e = Ce3+ (reduction half – reaction)
Adding
Fe2+ + Ce4+ = Fe3+ + Ce3+ (redox reaction)

6. Redox Reaction

7. Introduction
• Oxidation-reduction reactions are also known as
redox reactions
• Def: Redox reactions describe all chemical
reactions in which there is a net change in atomic
charge
• It is a class of reactions that include:
–formation of a compound from its elements
–all combustion reactions
–reactions that generate electricity
–reactions that produce cellular energy

8. We are talking about electricity
So we have
to talk
about
Luigi
Galvani

9. Galvanic Cells (cont.)
8H+ + MnO4
- + 5e- Mn2+ + 4H2O
Fe2+ Fe3+ + e- x 5

10. Galvanic Cells (cont.)
• In turns out that we still will not get electron flow
in the example cell. This is because charge build-
up results in truncation of the electron flow.
• We need to “complete the circuit” by allowing
positive ions to flow as well.
• We do this using a “salt bridge” which will allow
charge neutrality in each cell to be maintained.

11. Galvanic Cells (cont.)
Salt bridge/porous disk: allows for ion migration such
that the solutions will remain neutral.

12. Galvanic Cells (cont.)
• Galvanic Cell: Electrochemical cell in which chemical
reactions are used to create spontaneous current (electron)
flow