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Jessica Nunez 1I
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Postby Jessica Nunez 1I » Sun Feb 11, 2018 10:47 pm

What is the total entropy change of a process in which 40.0 kJ of energy is transferred as heat from a large reservoir at 800. K to one at 200. K?

For 9.5, the student solutions manual uses a negative sign for (delta)S = -40000 J/800 K, and I do not know why.

Jared Smith 1E
Posts: 51
Joined: Fri Sep 29, 2017 7:04 am

Re: 9.5

Postby Jared Smith 1E » Sun Feb 11, 2018 10:51 pm

I think that the reason that it is negative is due to the fact that the first reservoir lost heat, and transferred that heat to the second reservoir, meaning that it gained heat. Losing heat is negative, gaining is positive.

Jenny Cheng 2K
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Re: 9.5

Postby Jenny Cheng 2K » Fri Feb 23, 2018 2:35 pm

ΔS(total) = -q/T(1) + q/T(2)
The first reservoir loses heat, so the q should be negative. The second reservoir gains the heat that the first reservoir loses, so the q should be positive.

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Re: 9.5

Postby Kyung_Jin_Kim_1H » Sat Mar 17, 2018 11:38 pm

It is a transfer of heat, so thinking back to our ice cube in water problems, one will be positive and the other negative.

Troy Tavangar 1I
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Re: 9.5

Postby Troy Tavangar 1I » Sun Mar 18, 2018 12:54 am

It is because the first reservoir is losing heat.

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