Electrochemistry is the study of the interchange between chemical change and electrical work. Electrochemical cells utilize redox reactions to produce or use electrical energy. Redox reactions involve the transfer of electrons between oxidizing and reducing agents. Voltaic or galvanic cells generate electrical energy from a spontaneous redox reaction, while electrolytic cells use an applied electrical current to drive a nonspontaneous reaction. Common components of cells include electrodes, electrolytes, and salt bridges. Oxidation occurs at the anode and reduction at the cathode. Batteries contain multiple connected galvanic cells and electrolysis uses a current to force a nonspontaneous redox reaction.

1. Electrochemistry

2. Electrochemistry and Redox
Oxidation-reduction: “Redox”
Electrochemistry:
study of the interchange between chemical
change and electrical work
Electrochemical cells:
systems utilizing a redox reaction to produce
or use electrical energy

3. Redox Review
Redox reactions: electron transfer processes
Oxidation: loss of 1 or more e-
Reduction: gain of 1 or more e-
Oxidation numbers: imaginary charges
(Balancing redox reactions)

4. Oxidation-reduction
Oxidation is loss of e-
O.N. increases (more positive)
Reduction is gain of e-
O.N. decreases (more negative)
Oxidation involves loss OIL
Reduction involves gain RIG

5. Redox
Oxidation is loss of e-
causes reduction
“reducing agent”
Reduction is gain of e-
causes oxidation
“oxidizing agent”

7. Types of cells
Voltaic (galvanic) cells:
a spontaneous reaction generates electrical energy
Electrolytic cells:
absorb free energy from an electrical source to
drive a nonspontaneous reaction

8. Common Components
Electrodes:
conduct electricity between cell and
surroundings
Electrolyte:
mixture of ions involved in reaction or
carrying charge
Salt bridge:
completes circuit (provides charge balance)

9. Electrodes
Anode:
Oxidation occurs at the anode
Cathode:
Reduction occurs at the cathode
Active electrodes: participate in redox
Inactive: sites of ox. and red.

10. Voltaic (Galvanic) Cells
A device in which chemical energy
is changed to electrical energy.
Uses a spontaneous reaction.

11. 17_360
Porous disk
Reducing
agent
Oxidizing
agent
e –
e –
e – e –
e –
e –
CathodeAnode (b)(a)
Oxidation Reduction

15. Zn2+
(aq) + Cu(s)  Cu2+
(aq) + Zn(s)
Zn gives up electrons to Cu
— “pushes harder” on e-
— greater potential energy
— greater “electrical potential”
Spontaneous reaction due to
— relative difference in metals’ abilities to give e-
— ability of e- to flow

16. Cell Potential
Cell Potential / Electromotive Force (EMF):
The “pull” or driving force on electrons
Measured voltage (potential difference)
V
C
J
movedchargeofunit
energypotentialelectricalorwork
Ecell 

17. 17_363
e–
e– e–
e–
Zn 2+
SO4
2–
Zn(s)
1.0 M Zn 2+
solution
Anode
1.0 M Cu 2+
solution
Cathode
Cu 2+
SO4
2–
Cu(s)
Ecell = +1.10 V

23. 17_366
e–
e–e–
e–
Ag
1 M Ag+
1 M NO3
–
Anode Cathode
Porous
disk
Ag
0.1 M Ag+
0.1 M NO3
–

25. Batteries
A battery is a galvanic cell or, more
commonly, a group of galvanic
cells connected in series.

34. Corrosion
Some metals, such as copper, gold, silver and
platinum, are relatively difficult to oxidize.
These are often called noble metals.

37. Electrolysis
Forcing a current through a cell to
produce a chemical change for
which the cell potential is negative.