# Homework Help: Internal energy change

1. Jun 15, 2006

I need a little starter on this one....can't figure out how to do it(or even start it)....I'll work it, if I can get some help along the way....

Two moles of an ideal gas at 20 deg C undergo a free adiabatic expansion from 2.0 liters to 66 liters. Then the gas is adiabatically compressed such that the pressure is inversely proportional to the square of the volume: P=P(not)(V(not)/V)^2. What is the total internal energy change after both processes if the last compression reduces the volume by a factor of 4.

The problem is kinda hard to understand in itself for me....so any help would be greatly appreciated.

Thanks,

2. Jun 15, 2006

anyone else understand this problem enough to help me along??

3. Jun 15, 2006

### Andrew Mason

What is the relationship between Pressure and Volume in an adiabatic compression or expansion? (Hint: it depends on CP/CV for the gas. How do you determine $\gamma$ for this particular gas?)

What is the expression for the internal energy of a gas? (what property does it depend on?) Can you determine that property from the information provided?

AM

Last edited: Jun 15, 2006