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Chapter 7 Electrochemistry

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Title: Chapter 7 Electrochemistry


1
Chapter 7 Electrochemistry
7.3 Applications of Conductivity Measurement
  • Main contents
  • Monitoring the purity of water
  • Measurement of ionizability
  • Determination of solubility product and ionic
    product
  • Conductometric titration

2
1. Monitor the purity of water
Group works Calculate the conductivity of
pure water. at 25 oC, Kw 10-14, H OH?
10-7 moldm-3
water Tap water Distilled water Deionized water Pure water
?/Sm-1 1 ?10-2 1 ?10-3 lt1 ?10-4 5.478 ?10-6
Fabrication of VLSI
3
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-1
H2O2/NH3 SC standard cleaning,
SC-2 H2O2/HCl.
4
2. Measure the ionizability and dissociation
constant
c ?c
At infinite dilution
Arrhenius suggested that the degree of
dissociation of an electrolyte can be calculated
using molar conductivity.
5
Ostwald showed how one can measure the
dissociation constant of an acid.
Ostwald dilution law
The equation can be rearranged to
Linearization
6
3. Determine solubility and solubility products
Example The conductivity of a saturated AgCl
solution is 1.86 ? 10-4 Sm-1, while that for
water is 6.0 ? 10-6 Sm-1. Molar conductivity of
AgCl is 0.01372 Smol-1m2. Calculate the
solubility product for AgCl.
7
5. Determine ion product of water
Water can be taken as a dilute solution of a
strong electrolyte
CH COH- Kw1/2
The specific conductance of highly purified water
is 5.478 ?10-6 Sm-1. Calculate the concentration
of hydrogen ion in water.
8
6. Conductometric titration
The conductance variation of a solution during
titration can serve as a useful method to follow
the course of the reaction.
Ionic mobility of ions
Na OH- (HCl) 5.19 20.52
Na Cl- (H Cl-) 5.19 7.91
36.30
Precipitation reactions, neutralization
reactions, and coordination reactions
9
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10
Homework
Due time Sep. 24
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