Conductivity:
Ohm’s Law:  = IR
+
20.0 mV ~
L

L
–
A
R
Na+
Cll
R
Na+
l
A
Conductance: G = 1/R
x
1 l Gl
Conductivity:  = R A = A
 
l
 
cell constant = A
 
1 S = 1 ohm-1 = 1 mho
1 mS m-1 = 1x10-3 S m-1
1 S m-1 = 1 S cm-1(100 cm/1 m)

Molar conductivity: m = c
1 S cm-1 = 1x10-6 S cm-1
1 S cm-1 = 1 mS m-1(1 m/100 cm)(1000 S/1 mS)
 = m c
 m =  m – K c½
o
 = (m – K c½ ) c = m c – K c3/2
o
o
m = ++ + - M+XNa+
K+
H+
Ca2+
+
5.09
7.45
35.0
12.0
Colby College
ClNO3OHSO42-
o
example: Na2SO4
 – (mS m2 mol-1)
7.55
7.06
19.2
15.8
+ = 2 and - = 1
m = 2(5.09) + 1(15.8)
= 25.98 mS m2 mol-1
0.01 M
0.1 M
22.488
17.996 mS m 2 mol-1
0.100 M Na2SO4
0.001 M
24.83
o