## 8.27

isochoric/isometric: $\Delta V = 0$
isothermal: $\Delta T = 0$
isobaric: $\Delta P = 0$

Erick_Hernandez_3L
Posts: 20
Joined: Sat Jul 09, 2016 3:00 am

### 8.27

How do set up the equation for 8.27b.?
What is the difference in equations between an irreversible expansion with constant pressure and an isothermal reversible expansion?

"Calculate the work for each of the following processes beginning with a gas sample in a piston assembly with
T = 305 K, P = 1.79 atm, and V = 4.29 L: (a) irreversible expansion against a constant external pressure of 1.00 atm
to a final volume of 6.52 L; (b) isothermal, reversible expansion to a final volume of 6.52 L."

Rachel_Prescott_2M
Posts: 10
Joined: Wed Sep 21, 2016 2:57 pm
Been upvoted: 1 time

### Re: 8.27

The equation used for part a, when the reaction is irreversible and against a constant pressure, is w=-P(v2-v1) whereas the equation used for an isothermal and reversible expansion is w=-nRTln(v2/v1). For part b, the reaction may not be taking place with a constant pressure so the usual w=-P(v2-v1) equation can't be used. First calculate the number of moles of the gas using the initial volume and the ideal gas law, then take this value and plug it into w=-nRTln(v2/v1) and you should be able to find the work. Hope this helped!

Erick_Hernandez_3L
Posts: 20
Joined: Sat Jul 09, 2016 3:00 am

Thanks!