Irreversible Expansion vs. Reversible Expansion


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Alexia Joseph 2B
Posts: 56
Joined: Thu Jul 27, 2017 3:01 am

Irreversible Expansion vs. Reversible Expansion

Postby Alexia Joseph 2B » Fri Mar 16, 2018 12:39 am

I'm still kind of confused going, how can you tell if something is expanding irreversibly vs. reversibly?

Sean Monji 2B
Posts: 66
Joined: Fri Sep 29, 2017 7:06 am

Re: Irreversible Expansion vs. Reversible Expansion

Postby Sean Monji 2B » Fri Mar 16, 2018 9:19 am

Usually the problem will tell you directly, but if not: If the problem gives you a constant external pressure, the expansion should be irreversible; but if the pressure is increasing in miniature steps, the expansion should be reversible.
Irreversible has a noticeable difference between the internal and external pressure; reversible has a infinitely small difference in internal and external while the external pressure is decreasing in small steps.
Hope that helps

Sally Nason - 1K
Posts: 40
Joined: Fri Sep 29, 2017 7:05 am

Re: Irreversible Expansion vs. Reversible Expansion

Postby Sally Nason - 1K » Fri Mar 16, 2018 10:48 am

Since you use the equation w = -P*deltaV for irreversible expansion, you would likely be given the pressure or the change in moles to use for substitution with PV = nRT. For reversible expansion, we use the equation w = -nRT*ln(V2/V1) so you would likely be told it is isothermal and the moles would not change. These are just little things to look for to help determine which equation to use.


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