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Old Nov 21st 2009, 04:14 PM   #1
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Smile Entropy as a State function

Here is the question i am having trouble with -
Calculate the entropy of an ideal gas as a function of U, V and n at constant mole number solely by using the conditions:
pV=nRT (1)
U=3/2*nRT (2)
dU=Tds-pdV at n=const. (3)

I Have gotten to the point where I have
dS=(1/T)dU+(p/T)dV+(u/T)dn

I know that I need to integrate but not sure what to do from here.
Any help would be greatly appreciated
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Old Nov 21st 2009, 11:03 PM   #2
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answering this solely by mathematics(without knowing physics)
dS=(dU + P dV)/T=dU/T +P/T dV=3/2 nR dT/T + nRdV/V
integrating, S=3/2 nR lnT +nRlnV +C=nR ln(T^3/2V) + C
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