1. Introduction to mixtures (more in 3rd year)
Thermodynamics handout
Introduction to mixtures (more in 3rd year)
Deal only with homogeneous mixtures of a solvent (major component) and solute (minor component).
Introduce partial molar property: contribution that a substance makes to overall property.
V = nAVA + nBVB
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2. The chemical potential, m
We can extend the concept of partial molar properties to state functions, such as Gibbs energy, G.
This is so important that it is given a special name and symbol, the chemical potential, m.
G = nAGA + nBGB
G = nAmA + nBmB

3. Blank-to be presented in Lecture

4. Thermodynamics handout
Chemical Equilibria
DG = DH – TDS
In a spontaneous change at constant temperature and pressure, the Gibbs energy decreases
A reaction mixture, at constant T and p, adjusts its composition until its Gibbs energy is a minimum
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5. Thermodynamics handout
Reaction Gibbs energy
For a general reaction:
aA + bB  cC + dD
DrG = (cmC +dmD)-(amA + bmB)
Note error in eqn 7.1c in textbook
At equilibrium
DrG = 0
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6. Variation of DrG with composition
Thermodynamics handout
Variation of DrG with composition
Can derive that: mJ = mJ° + RT ln aJ
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7. Variation of DrG with composition
Thermodynamics handout
Variation of DrG with composition
mJ = mJ° + RT ln aJ
DrG = (cmC +dmD)-(amA + bmB)
=DrG°
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8. Blank-to be presented in Lecture

9. Spontaneity again

10. Thermodynamics handout
Summary
The chemical potential of a substance is a measure of the ability of the substance to bring about change.
Reaction Gibbs energies represent the slope of a plot of Gibbs energy versus composition, and represents the tendency for a process to approach equilibrium.
Reaction Gibbs energies are zero at equilibrium, and the standard Gibbs energy change is related to the equilibrium constant.
Spontaneous processes possess negative standard Gibbs energy changes and have K greater than 1.
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