Chapter 7 Electrochemistry - Shandong...
Transcript of Chapter 7 Electrochemistry - Shandong...
Chapter 7 Electrochemistry
§7.3 Applications of Conductivity Measurement
1. Monitor the purity of water
Silicon wafer
Integrated circuit
Fabrication of VLSI
§7.3 Applications of Conductivity Measurement
1. Monitor the purity of water Fabrication of VLSI
§7.3 Applications of Conductivity Measurement
Silicon wafer
In-situ monitoring of the cleaning
process: H2O2/H2SO4 → DW rinse →
dilute HF → SC-1 cleaning → DW
rinse → hot DW rinse → DW rinse →
SC-2 cleaning → DW rinse → dilute
HF → DW rinse.
DW⎯deionized water,
SC ⎯ standard cleaning:
SC-1: H2O2/NH3; SC-2: H2O2/HCl.
1. Monitor the purity of water Fabrication of VLSI
water Tap
water
Distilled
water
Deionized
water
Pure
water
/S·m-1 1 10-2 ~1 10-3 <1 10-4 5.478 10-6
§7.3 Applications of Conductivity Measurement
2. Measure the ionizability and dissociation constant
m
( )c Z F U U
c + + + −+
=c+ =c
m ( )U U F + −= +
At infinite dilution
m ( )F U U
+ −= +
m
m
( )
( )
U U F
U U F
+ −
+ −
+= =
+
Arrhenius suggested that the degree of
dissociation of an electrolyte can be
calculated using molar conductivity.
§7.3 Applications of Conductivity Measurement
22 2 2
m
m m m(1 ) 1 ( )
cc cK
c
= = =
− − −
Ostwald dilution law
Ostwald showed how one can measure the
dissociation constant of an acid.
The equation can be rearranged to
m2
m m m
1 1 1( )
a
cK
= +
Linearization
2. Measure the ionizability and dissociation constant
§7.3 Applications of Conductivity Measurement
3. Determine solubility and solubility products
-Ag Ag Cl Cl H H OH OHc c c c + + − + + − −= + + +
w Ag Ag Cl Cl Ag Cl( )c c S + + − − + −− = + = +
w w
mAg Cl
S
+ −
− −= =
+
Example: The conductivity of a saturated
AgCl solution is 1.86 10-4 S·m-1, while
that of water used for preparation the
solution is 6.0 10-6 S·m-1. Given that the
molar conductivity of AgCl is 0.01372
S·mol-1·m2. Calculate the solubility
product for AgCl. What assumption have we made?
§7.3 Applications of Conductivity Measurement
4. Determine ion product of water
Water can be taken as a dilute solution
of a strong electrolyte
CH+ = COH- = Kw1/2
m m,H m,OHc
+ −
= = +
The specific conductance of highly purified
water is 5.478 10-6 S·m-1. Calculate the
concentration of hydrogen ion in water.
-1 2
m m,H m,OH0.05481S mol m + −
= + =
6 1
1 2
m
4 3
7 3
5.478 10 S m
0.05481S mol m
0.9995 10 mol m
1 10 mol dm
c
− −
−
− −
− −
= =
=
§7.3 Applications of Conductivity Measurement
5. Conductometric titration (the way to determine endpoint)
The conductance variation of a solution
during titration can serve as a useful
method to follow the course of the
reaction.
Na+ + OH- + (HCl) = Na+ + Cl- + (H+ + Cl-)
5.19 20.52 5.19 7.91 36.30
Precipitation reactions,
neutralization reactions,
coordination reactions
A
B
C
A’
B’
C’
V / ml
/
S·m
-1
endpoint
§7.3 Applications of Conductivity Measurement
5. Conductometric titration
§7.3 Applications of Conductivity Measurement
6. Study on ionic channel in cell membrane
§7.3 Applications of Conductivity Measurement
6. Study on ionic channel in cell membrane
§7.3 Applications of Conductivity Measurement