work


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Nahelly Alfaro-2C
Posts: 59
Joined: Wed Nov 15, 2017 3:04 am

work

Postby Nahelly Alfaro-2C » Sun Feb 17, 2019 5:16 pm

Just a verification for work equations:
We would use W=-Pdelta V when pressure is constant and W=-nRTln(V2/V1) when pressure is not constant?

Julia Go 2L
Posts: 60
Joined: Sun Sep 30, 2018 12:17 am
Been upvoted: 1 time

Re: work

Postby Julia Go 2L » Sun Feb 17, 2019 5:21 pm

We need to calculate work when there is expansion work done. So firstly, there must be a change in volume.

Under constant pressure:
W=-Pdelta V

Under constant temperature: (isothermal, reversible)
W=-nRTln(V2/V1)

WilliamNguyen_4L
Posts: 65
Joined: Fri Sep 28, 2018 12:28 am

Re: work

Postby WilliamNguyen_4L » Sun Feb 17, 2019 5:24 pm

Yes, we use W=-pdeltav when the process is irreversible and pressure can be constant in that case. We use W=-nRTln(V2/V1) when the process is reversible and that's when pressure and volume can both not be constant. In a irreversible process if the pressure is not constant and volume is constant no work is done.


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