# Thermodynamics - know process, work and change in entropy. Final temperature?

1. Sep 14, 2008

### HHveluj

So, the problem is:
A 200-gram sample of dry air is heated isobarically. Its entropy increases by 19.2 J/K and the work done by expansion is 1.61x103 J. Solve for the final temperature of the air.

Okay, since p=const => dq=CpdT thus instead of dq=du+dw we can write
dq=dq(Cv/Cp)+dw
can find dq=460.46
So i know dq,du,dw,d$$\phi$$, but how do I get final temperature? All I can find is dT but it's useless sine I don't know initial temperature.
And where do I put mass and how to use the d$$\phi$$=dq/T formula? Looks like it will be needed here...

Thanks a lot in advance!

2. Sep 14, 2008

### HHveluj

nevermind. solved it.

3. Sep 14, 2008

### smileystorm

Aw. I have this problem too and I'm stuck on it. :(

4. Sep 14, 2008

### HHveluj

Get Tfinal - Tinitial through work, then you can solve integral dphi=dq/t and get the answer for Tfinal.

5. Sep 16, 2008

### cec06c

I have this problem too and i still do not understand how you can solve for T final if there is not an initial temp given.

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