Sep 2, 2010
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This question is from the princeton review gen chem book and I cant figure out why this is the answer:

For a perfectly insulated system, what are the values of ΔE internal and q if w = +100 J .

The answer is:

ΔE = + 100 J and q = 0 .

Now, I understand why q = 0 , as this is the definition of a adiabatic process.

However, I thought that during adiabatic processes, since q = 0, ΔE internal = -w .

As w = + 100 J , wouldnt the answer be:


ΔE = - 100 J and q = 0 ?

Thanks!
 

Isoprop

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ΔE = q + w

q = 0 J; w = 100 J

ΔE = 0 J + 100 J
= 100 J
 
Jun 18, 2010
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Different books use different terminology. Some say that positive work means work flowing into the system, or work done on the gas. Some define positive work to be work done by the system, or work flowing out of the system.
 
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Isoprop

Fascinating, tell me more
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Oct 15, 2007
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Medical Student
Different books use different terminology. Some say that positive work means work flowing into the system, or work done by the gas. Some define positive work to be work done by the system, or work flowing out of the system.
Yes. Unless otherwise told, you should assume positive work means "into the system" on the MCAT.