Delta U equals zero


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Matt Sanruk 2H
Posts: 131
Joined: Wed Sep 18, 2019 12:21 am

Delta U equals zero

Postby Matt Sanruk 2H » Wed Feb 05, 2020 11:58 pm

What would be an example of delta U equaling to zero?

Adriana_4F
Posts: 74
Joined: Fri Sep 28, 2018 12:29 am

Re: Delta U equals zero

Postby Adriana_4F » Thu Feb 06, 2020 12:03 am

An isothermal expansion

One of the characteristics of an ideal gas is that there is no interaction between gas molecules. This means the molecules will not have any potential energy so the only contributor to the change in internal energy would be its kinetic energy due to its absolute temperature. Since it is isothermal, T=0 so neither kinetic nor potential energy would contribute to the change in internal energy so deltaU=0.

Matt Sanruk 2H
Posts: 131
Joined: Wed Sep 18, 2019 12:21 am

Re: Delta U equals zero

Postby Matt Sanruk 2H » Thu Feb 06, 2020 1:14 am

So this is for constant pressure and ideal gas?

Zaynab Hashm 2I
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Joined: Wed Sep 11, 2019 12:15 am
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Re: Delta U equals zero

Postby Zaynab Hashm 2I » Thu Feb 06, 2020 1:36 am

it would be for an isothermal reaction when the temperature is constant

Matt Sanruk 2H
Posts: 131
Joined: Wed Sep 18, 2019 12:21 am

Re: Delta U equals zero

Postby Matt Sanruk 2H » Thu Feb 06, 2020 1:03 pm

Sorry yes I meant temperature, thanks!

Anthony Hatashita 4H
Posts: 103
Joined: Wed Sep 18, 2019 12:21 am

Re: Delta U equals zero

Postby Anthony Hatashita 4H » Thu Feb 06, 2020 8:03 pm

Considering the first law equation, work and heat would have to equal 0. For an isothermal process, heat is 0, so if there is a reaction that is isothermal that does no work, delta U should be 0.

205291012
Posts: 50
Joined: Mon Nov 11, 2019 12:17 am

Re: Delta U equals zero

Postby 205291012 » Thu Feb 06, 2020 10:07 pm

delta U would be 0 if it is isothermal and no work is done. imagine a gas expanding in a vacuum with constant temperature. since it is not pushing against anything, no work is done and there is no change in temperature so delta U is 0.

Sean Cheah 1E
Posts: 105
Joined: Wed Sep 18, 2019 12:20 am

Re: Delta U equals zero

Postby Sean Cheah 1E » Fri Feb 07, 2020 11:08 am

As noted previously, all isothermal processes by definition have delta U = 0. This means that the work done does not necessarily have to be 0. In the case that work is not zero, q will simply be the negative of that so they cancel out.


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