Constant External Pressure


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Carlos Gonzales 1H
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Joined: Fri Sep 29, 2017 7:05 am
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Constant External Pressure

Postby Carlos Gonzales 1H » Sun Jan 14, 2018 8:47 pm

One of the equations we are given for work is w=-PexΔV, where external pressure is constant. Will the pressure always be constant or are there instances where the pressure will be different?

Simrina Desar Dis 1H
Posts: 49
Joined: Fri Sep 29, 2017 7:04 am

Re: Constant External Pressure

Postby Simrina Desar Dis 1H » Sun Jan 14, 2018 11:41 pm

Also, why does this pressure have to be constant? What will happen if it varies?

Nancy Dinh 2J
Posts: 59
Joined: Fri Sep 29, 2017 7:07 am

Re: Constant External Pressure

Postby Nancy Dinh 2J » Mon Jan 15, 2018 1:27 pm

Carlos Gonzales 1H wrote:One of the equations we are given for work is w=-PexΔV, where external pressure is constant. Will the pressure always be constant or are there instances where the pressure will be different?


For that equation to be used, the pressure has to be constant. However, if the pressure is not constant, then you have a reversible process on your hands and will have to use the the equation w = - nRT ln(Vf/Vi). In Example 8.2, the book solves a problem where pressure is either constant or not.


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