Reversible and Irreversible Paths:
A Computer Application
I n introductory physical chemistry courses the difference in the work obtained along reversible and irreversible paths is stressed. But students often find it difficult to get s. feeling for the approach of multistep irreversible paths t o a reversible one. A partial solution has been found here that also exposes students to computer applications. After only a few hours of instruction in computer ~rogrsmrning,a student (G.S.) has written R. Fortran IV program t o investigate the work done on the expansion a t 25-C of 1 1 of an ideal gas from 10 to 1atm along various paths. Path (a) free expansion against eero pressure (b) 1 step against a. pressure of 1 atm (e) 10 steps, each ageinst a pressure of 1atm
W ( l atm)
WIWIa.
0.00 9.00
0,000 0.391
less than the pressure on the gas (i.e., from 10 t o 9 s t m against 9 rttm, from 9 t o 8 against 8 atm. etc.) 19.29 0.838 (d) 100 such steps, each against a pressure 0.1 atm less 22.58 0.980 ( a ) 1000 such steps, each against a. pressure 0.01 atm 22.98 0.998 less (f) reversible 23.03 1.000 From such calculations, which are too time-consuming t o be done by hand, the student can gain an appreciation for such terms. This is another example where the computer can assist the learning process.
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CENTUL MICHIGAN UNIVERSITY 48858 MOUNTPLEASANT,
51 8
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Journal of Chemical Education
