Chemistry Reference
In-Depth Information
•
Conductometric methods
: in conductometric methods, the conductivity
of an electrolyte is assessed by measuring the impedance of this system
using two identical electrodes, planarly positioned. However, much
more can be done if the impedance is measured as a function of applied
frequency, a method that is called electrochemical impedance spec-
troscopy; more details about this method are given in section 2.3.
1.5
Two-electrode setup
In potentiometry, a two-electrode setup is used and is given schematically
in Fig. 1.3. This setup consists of a working and a reference electrode, and
it is the aim of this method to measure equilibrium conditions at the surface
of the working electrode. Under equilibrium, the Nernst equation is valid:
a
a
a
a
R
T
R
T
0
0
EE
=+
0
ln
=+
E
0
23
.
log
eq
n
F
n
F
R
R
c
c
¢
+
R
T
0
0
=
E
23
.
log
[1.8]
n
F
R
where
E
eq
is the measured equilibrium potential (V),
E
0
is the standard
potential (V),
E
0¢
is the formal potential (V), R is the universal gas constant
(8.317 J mol
-1
K
-1
),
T
is the temperature (K),
n
is the number of electrons, F
V
RE
WE
1.3
Scheme of a potentiometric setup, showing reference electrode
(RE) and working electrode (WE).
