delta U  [ENDORSED]

isochoric/isometric:
isothermal:
isobaric:

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Hector Acosta Discussion 1H
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Joined: Fri Sep 29, 2017 7:04 am

delta U

Postby Hector Acosta Discussion 1H » Fri Feb 09, 2018 5:42 pm

If there is no change in temperature is 0?

Mitch Mologne 1A
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Re: delta U

Postby Mitch Mologne 1A » Fri Feb 09, 2018 6:06 pm

Not necessarily. There can be work done.

Gianna Apoderado 1B
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Re: delta U

Postby Gianna Apoderado 1B » Fri Feb 09, 2018 8:24 pm

Yes, like Mitch said above, delta U has two components, as seen in the equation deltaU = q + w (the first law of thermodynamics). Even if change in temperature is 0, and q is 0, work can still be done and affect internal energy.

Chem_Mod
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Re: delta U  [ENDORSED]

Postby Chem_Mod » Fri Feb 09, 2018 8:34 pm

If there is no change in temperature in an ideal gas then Delta U is always zero.

However, that does not mean q = 0 and w = 0.

As I discussed in class for the isothermal expansion of an ideal gas: q = -w (meaning they cancel each other resulting in Delta U = 0)

Ask about this in my Monday review session.

DianaTrujillo2K
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Re: delta U

Postby DianaTrujillo2K » Tue Feb 13, 2018 3:58 pm

Can someone explain why delta U is 0 in the isothermal expansion of an ideal gas?

ClaireHW
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Re: delta U

Postby ClaireHW » Tue Feb 13, 2018 4:33 pm

Can someone also explain under what conditions is delta U equal to zero?

(Claire Woolson Dis 1K)

Sophie 1I
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Re: delta U

Postby Sophie 1I » Wed Feb 14, 2018 11:42 am

I know that delta U is 0 for isothermal reactions but I'm not sure why that is

Toru Fiberesima 1L
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Re: delta U

Postby Toru Fiberesima 1L » Mon Feb 11, 2019 11:48 am

Recall that dU=q+w. For an isothermal expansion q=-w. Also, temperature does not change (hence isothermal), therefore q=0. If q=0 then w=0. Thus, dU=0+0=0.

Joanna Pham - 2D
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Re: delta U

Postby Joanna Pham - 2D » Tue Feb 12, 2019 9:17 am

In lecture yesterday for one of the review problems that asked to calculate deltaS of an isothermal reaction, Lavelle mentioned that U = (3/2)nRT. Thus, If there’s no change in temperature, since n, R, and T are all constant, that means there’s no change in internal energy.

Madeline Ho 1C
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Re: delta U

Postby Madeline Ho 1C » Tue Feb 12, 2019 12:53 pm

With isothermal reversible expansion, work of expansion is being done by the system so energy is being lost. However, a heat reservoir also adds heat back into the system, so temperature remains constant. This is why q=-w.

JT Wechsler 2B
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Re: delta U

Postby JT Wechsler 2B » Tue Feb 12, 2019 1:53 pm

deltaU can equal 0 when there is no temperature change or q is equal to -w.


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