Adiabatic vs. Isothermal Expansion: How to Calculate Work and Temperature?

[bio87]

Hi people!
So i have a homework question that i am stuck on!

Four moles of an ideal monatomic gas undergoes an adiabatic expansion from intial volume of 1m cubed and a temperature of 300k to a final volume of 10m cubed. a) How much wrk is done by the gas ? b) what is the final temperature? c) If instead the gas expands isothermally to 10m cubed, how much work is done? d) In part C where does the energy come from to perform the work? ...thats a lot!

I thought of using the equation of work W(by)= 1/(1-gamma) x (PfVf-PiVi) to fnd the answer for a...but I don't have the pressure.. then i thought that maybe I could use deltaE= Q(in) - W (by)...but I don't know the change in temperature, therefore; I am all over the place and I don't know where to start.. any hints/help would be appreciated! Thanks

 

[hage567]

With the information you were given, you can find the initial pressure of the gas.

 

[Andrew Mason]

I thought of using the equation of work W(by)= 1/(1-gamma) x (PfVf-PiVi) to fnd the answer for a...but I don't have the pressure..

First work out the initial pressure, which is easy since you are given n,Ti and Vi.
What is the relationship between P and V in an adiabatic expansion/compression? (hint: it involves $\gamma$). That will give you the final pressure and, if you know n, Vf and Pf you can determine Tf.

AM