361 Lec23
Tue 6oct15
Yesterday we found that ξ0’ =0.16
First, qualitatively by Lechatelier,
will ξ0 be more positive or more negative than ξ0’?
Will shift LEFT; ξ0 is 1 molar H+; less spontaneous
so ξ0 more negative than ξ0’;
What equation to use to get ξ0 if you know ξ0’?
We will use 5.7 kJ/mol in ∆G0 changes Q by factor of 10,
and ξ0 = ∆G0/(-nF). F= 96,500 = ~100 kJ/mol
so ~ -0.057/n volts per power of 10 (how a pH meter works)
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What is implied
here? Q/Q0
Always!
2.3 x 8.3145 x 298 =5700
5700/96,500 = 0.05916
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ξ0
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361Lec23
Tue 6oct15
6
11
Including what is
outside of cell.
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Return to Chap. 7 for this
ALSO:
vapor pressure of diluted water
solubility and vapor pressure
of gases in water
partition of solutes between
different solvents
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Phase 1
A
B
Phase 2
A
B
A
B
Phase 3
A
B
The Guiding Principle:
At equilibrium the chemical
potential of a solute or solvent
will be the same in ALL phases
This is equivalent to saying the activity for each
component in the system will be the same in ALL
phases (if the same standard state is used in each
phase)
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similar to
Fig. 6.3
Recall: “Vapor Pressure = partial pressure But, for the SOLID-LIQUID equilibrium
of gas in equilibrium with its liquid. peq is the APPLIED PRESSURE
pH2O =(nH2O/V) RT =[H2O] RT
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