### reversible vs irreversible

Posted:

**Sun Jan 14, 2018 5:36 pm**What are the two equations that are used for reversible and irreversible reactions and how do you differentiate between the processes if not told in the problem?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=128&t=25489

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Posted: **Sun Jan 14, 2018 5:36 pm**

What are the two equations that are used for reversible and irreversible reactions and how do you differentiate between the processes if not told in the problem?

Posted: **Sun Jan 14, 2018 6:21 pm**

The reversible expansion of an ideal gas has a pressure that keeps changing, so you have to use an integral to find the area under the curve. The equation that is used for reversible expansion is w=-nRTln(V2/V1)

The irreversible expansion is against a constant external pressure, so you don't need an integral (just find the area of a rectangle). The equation used for irreversible expansion is w=-P ΔV

The irreversible expansion is against a constant external pressure, so you don't need an integral (just find the area of a rectangle). The equation used for irreversible expansion is w=-P ΔV

Posted: **Sun Jan 14, 2018 7:49 pm**

I think what's also important to note is that a change that is done reversibly does more work than a change carried out irreversibly if you are asked to identify in that instance which is reversible and which is irreversible. This is provided that the initial and final states are the same.