PChem312 f22 w12
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Wednesday, Nov 11, 2020
- Review contributions to ΔS due to ΔT, ΔV, ΔP for ideal gas/closed system.
- Entropy of Phase Changes...
...continuing numbering from above...
- 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.
- 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;
- At constant P;
- At constant V;
- where,
- At constant V;
- and Δn is the change in moles of gas (Products - reactants; ie. increase in the number of moles of gas)
Example Problem 3
(Please write out your complete solution and email to bes by next class period)
- Poly aromatic hydrocarbons (<-- wiki link here) represent and interesting set of compounds.
Calculate the entropy of fusion for 5 PAHs.