Difference between revisions of "PChem312 f22 w12"

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::::::[[File:Screen Shot 2020-11-13 at 8.06.56 AM.png|175px]]
 
::::::[[File:Screen Shot 2020-11-13 at 8.06.56 AM.png|175px]]
 
:::::: and Δn is the change in moles of gas (Products - reactants; ie. increase in the number of moles of gas)
 
:::::: and Δn is the change in moles of gas (Products - reactants; ie. increase in the number of moles of gas)
 
====Example Problem 3====
 
Calculate the entropy of fusion for 5 PAHs.
 
 
[https://en.wikipedia.org/wiki/Polycyclic_aromatic_hydrocarbon Poly aromatic hydrocarbons] (<-- wiki link here) represent and interesting set of compounds.
 
 
[[File:PAH.PNG|800px]]
 

Revision as of 13:47, 21 November 2022

Entropy of Phase Changes...

...continuing numbering from notes...

5) Solid --> Liquid phase change (fusion/melting/freezing)
- under constant pressure (ΔH)
- under constant volume (ΔU)
For processes involving solids and liquids, ΔH ~ ΔU, hence ΔS is the same for both constant P and constant V.
Screen Shot 2020-11-13 at 7.55.16 AM.png
6) Liquid --> gas phase change (vaporization/boiling/condensation)
- under constant pressure (ΔH)
- under constant volume (ΔU)
For processes involving gases, ΔH ≠ ΔU, hence ΔS is not the same for constant P and constant V processes.
At constant P;
Screen Shot 2020-11-13 at 7.58.25 AM.png
At constant V;
Screen Shot 2020-11-13 at 8.05.55 AM.png
where,
Screen Shot 2020-11-13 at 8.06.56 AM.png
and Δn is the change in moles of gas (Products - reactants; ie. increase in the number of moles of gas)