Cp/Cv

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605110118
Posts: 75
Joined: Wed Sep 18, 2019 12:21 am

Cp/Cv

Postby 605110118 » Thu Feb 06, 2020 4:36 pm

If an entropy/delta T problem doesn't specifically state it, do we assume it is at constant pressure or constant volume?

SnehinRajkumar1L
Posts: 101
Joined: Thu Jul 11, 2019 12:15 am

Re: Cp/Cv

Postby SnehinRajkumar1L » Thu Feb 06, 2020 5:39 pm

You should assume constant pressure.

Shrayes Raman
Posts: 129
Joined: Sat Jul 20, 2019 12:15 am

Re: Cp/Cv

Postby Shrayes Raman » Fri Feb 07, 2020 12:31 am

constant pressure is assumed unless otherwise specified as we have the equation nRT ln(v2/v1) assumes constant pressure

Fatemah Yacoub 1F
Posts: 114
Joined: Thu Jul 11, 2019 12:16 am

Re: Cp/Cv

Postby Fatemah Yacoub 1F » Fri Feb 07, 2020 10:22 am

You must assume that it is constant pressure because otherwise you a reversible system which requires another set of equations.

stephaniekim2K
Posts: 79
Joined: Fri Aug 09, 2019 12:16 am

Re: Cp/Cv

Postby stephaniekim2K » Sun Feb 09, 2020 7:14 pm

Unless stated, just assume that it is at constant pressure.

Max Madrzyk Dis 4G
Posts: 102
Joined: Wed Sep 18, 2019 12:21 am

Re: Cp/Cv

Postby Max Madrzyk Dis 4G » Sun Feb 09, 2020 7:18 pm

You can usually assume constant pressure because usually reactions arn't moved to different pressures throughout the course of the reaction. for example a chemist starting a reaction at sea level will probably let the reaction finish at sea level. This is true for most reactions with engines being an exception.

Sjeffrey_1C
Posts: 108
Joined: Wed Feb 20, 2019 12:17 am

Re: Cp/Cv

Postby Sjeffrey_1C » Sun Feb 09, 2020 7:19 pm

Fatemah Yacoub 1F wrote:You must assume that it is constant pressure because otherwise you a reversible system which requires another set of equations.


In this case, you'd use work = -nRT ln (v2/v1)

Callum Guo 1H
Posts: 134
Joined: Fri Aug 02, 2019 12:15 am
Been upvoted: 1 time

Re: Cp/Cv

Postby Callum Guo 1H » Sun Feb 09, 2020 7:27 pm

i think just assume constant pressure.


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