1. Sep 24, 2010

### nbram87

1. The problem statement, all variables and given/known data

Two moles of helium at 27 deg Celsius occupies 20 liters. The gas is expanded first at constant pressure until the volume has doubled, and then adiabatically until the temperature returns to its initial value Treat helium as an ideal monatomic gas and assume that both processes are quasistatic.
a) Determine the final volume
b) What is the heat supplied in the overall process?
c) What is the change in the internal energy?

2. Relevant equations
Ideal gas law PV=nrT

3. The attempt at a solution

I am confused with this problem, and what equations to use. Using the ideal gas law, I determined that with constant pressure and the volume doubling, the temperature would go to 600 degrees Kelvin. I am really confused with this problem. I appreciate any help!

2. Sep 25, 2010

### Andrew Mason

For a), determine the temperature after isobaric expansion using the ideal gas law. Then for the adiabatic part, determine the change in volume by applying the adiabatic condition.

For part b) how is heat flow related to work done by the gas? (hint: apply the first law and the answer to part c)).

AM