SLIDE 1
Thermochemistry
Start looking at techniques for chemical systems undergoing change.
Focus on constant pressure processes
Evaluate using tabulated heat capacities
CEM 484 Chemical Thermodynamics 2
Chemical Thermodynamics Thermochemistry Start looking at techniques - - PowerPoint PPT Presentation
Chemical Thermodynamics Thermochemistry Start looking at techniques - - PowerPoint PPT Presentation
Chemical Thermodynamics Thermochemistry Start looking at techniques for chemical systems undergoing change. Focus on constant pressure processes Evaluate using tabulated heat capacities Chemical Thermodynamics CEM 484 2
SLIDE 2
SLIDE 3
Thermochemistry
Remember heat capacity of an atomic solid.
From heat capacity, determine entropy.
CEM 484 Chemical Thermodynamics 3
SLIDE 4
3rd Law
3rd Law of thermodynamics defines the zero point for entropies.
Absolute reference scale not needed for enthalpies
CEM 484 Chemical Thermodynamics 4
SLIDE 5
Phase transitions
Integrating heat capacities over T works fine until a phase transition is encountered.
Phase transition results in discontinuities.
CEM 484 Chemical Thermodynamics 5
SLIDE 6
Phase transitions
Consider Gibbs free energy.
No discontinuities.
CEM 484 Chemical Thermodynamics 6
SLIDE 7
Example
Liquid C6H6 boils at Tb = 353 K with DvapH ̅ 0. C ̅ p
0 (l) = 135.1 J/Kmol and C
̅ p
0 (g) = 81.6 J/Kmol
Calculate DvapH ̅ 0 at 300 K.
CEM 484 Chemical Thermodynamics 7
SLIDE 8
Example
Calculate DvapS ̅ 0 at 300 K.
CEM 484 Chemical Thermodynamics 8
SLIDE 9
Generic
For generic chemical reaction.
CEM 484 Chemical Thermodynamics 9