Problem 8.49

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Kelsey Jug 1J
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Problem 8.49

Postby Kelsey Jug 1J » Thu Jan 12, 2017 3:17 pm

I'm having some trouble understanding homework problem 8.49.
It asks for the change in internal energy for the reaction of 1 mol of OF2 (g).
Why wouldn't the change in internal energy just be the delta H given?
Why do we have to take the work (-PdeltaV) into account?
What work is being done? Wouldn't all the change in energy be accounted for in the given delta H?

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Re: Problem 8.49

Postby Chem_Mod » Thu Jan 12, 2017 5:32 pm

Please mind the forum guidelines and post the full problem so anyone reading this can see it in context.

Andrew Nguyen 3G
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Re: Problem 8.49

Postby Andrew Nguyen 3G » Thu Jan 12, 2017 6:00 pm

Internal energy = q + w

Not only is energy being put into the system externally, but work is being done WITHIN the system itself, which also adds to internal energy. This is why internal energy is not just delta h.

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Re: Problem 8.49

Postby alondra_1D » Thu Jan 12, 2017 6:40 pm

I have another question regarding this problem,

do we assume that the temperature is 298.15K because 25 degrees celsius is most commonly used?

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Re: Problem 8.49

Postby Nick_Kopooshian_3C » Thu Jan 12, 2017 10:09 pm

I believe you use 298.15 K because in these specific cases you have to use the SATP (standard ambient temperature and pressure) standard which is a temperature of 298.15 K and a pressure of 1 atm.

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