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argali

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I am trying to teach myself the basics of thermodynamics using a book I bought from a university book store.

My question relates to the amount of work done by reversible vs irreversible processes. An example in the book (Chemical Principles by Atkins & Jones) reads the following:

"A cylinder of volume 2.00 L contains 0.100 mol He (g) at 30°C. Which process does more work on the system, compressing the gas isothermally to 1.00L with a constant external pressure of 5.00 atm or compressing it reversibly and isothermally to the same final volume?"

I know that reversible processes should always do the most work because the system is doing work against the maximum opposing force under the given conditions, but when I actually do the calculations here, I find that the irreversible process does more work.

To find the amount of work done by the irreversible process, I used P[itex]\Delta[/itex]V and convert the quantity to Joules using 101.325 J/(L*atm). I end up with 506.6J of work being done ON the system.

To find the amount of work done by the reversible process, I used -nRT * ln(V

This is seemingly inconsistent with the fact that reversible processes always do more work than irreversible processes. Could someone please explain where my logic has gone askew?

Thank you so much!

-argali

My question relates to the amount of work done by reversible vs irreversible processes. An example in the book (Chemical Principles by Atkins & Jones) reads the following:

"A cylinder of volume 2.00 L contains 0.100 mol He (g) at 30°C. Which process does more work on the system, compressing the gas isothermally to 1.00L with a constant external pressure of 5.00 atm or compressing it reversibly and isothermally to the same final volume?"

I know that reversible processes should always do the most work because the system is doing work against the maximum opposing force under the given conditions, but when I actually do the calculations here, I find that the irreversible process does more work.

To find the amount of work done by the irreversible process, I used P[itex]\Delta[/itex]V and convert the quantity to Joules using 101.325 J/(L*atm). I end up with 506.6J of work being done ON the system.

To find the amount of work done by the reversible process, I used -nRT * ln(V

_{final}/V_{initial}). I end up with 174.6 J of work being done on the system.This is seemingly inconsistent with the fact that reversible processes always do more work than irreversible processes. Could someone please explain where my logic has gone askew?

Thank you so much!

-argali

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