PChem312 f20 w13

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Monday, Nov 9, 2020

We will now highlight how to calculate entropy (ΔS) for four processes involving ideal gases:

1) Reversible Isothermal Expansion or Compression

V_iT_i --> V_fT_i

2) Constant P, V temperature change

V_iT_i --> V_iT_f

P_iT_i --> P_iT_f

3) Changes in both V and T, constant P

V_iT_i -->V _fT_f

4) Changes in both P and T, constant V

V_iT_i -->V _fT_f

Example Problem 1

(Please write out your complete solution and email to bes by next class period)

Consider a gas undergoing the following change under constant pressure (1.00 bar) conditions; calculate the change in entropy (ΔS): V_i = 10.0 L; T_i = 298 K; T_f = 398 K

Example Problem 2

(Please write out your complete solution and email to bes by next class period)

Consider a gas undergoing the following change under constant volume (10.0 L) conditions; calculate the change in entropy (ΔS): P_i = 1.00 bar; T_i = 298 K; T_f = 398 K

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

- under constant volume

6) Liquid --> gas phase change (vaporization/boiling/condensation)

- under constant pressure

- under constant volume

Example Problem 3

Poly aromatic hydrocarbons (<-- wiki link here) represent and interesting set of compounds.

Calculate the entropy of fusion for 5 PAHs.

Example Problem 4

Calculate the entropy of vaporization for methanol, ethanol, and propanol under both constant pressure and constant volume conditions.