NORTH CAROLINA STATE UNIVERSITY

Department of Chemistry Name________________________________

CH 431 Quiz 2

Physical Chemistry II Sept. 25, 2001

Due: Oct. 2, 2001

This is very good practice for the mid-term. When you turn this in you will receive a copy of the solutions for study purposes. The final due date is Sept. 15 at the mid-term.

1. A cylinder at 0.02 L is expanded and 20 atm is expanded to a volume of 0.4 L. The

initial temperature is 500 K

A. Calculate the final pressure and work done for a constant pressure process. Give your answer for the work in units of Joules.

B. Calculate the final pressure and the work done for an adiabatic process. Give your answer for the work in units of Joules.

C. Calculate the final pressure and work done for an isothermal process. Give your answer for the work in units of Joules.

D. Draw each of these processes on a P-V plot (use a separate piece of paper or the backside of this sheet).

2. A two level system shown below consists of a spin in a magnetic field. The magnetic field produces a splitting the energy levels of spins aligned with and opposing the magnetic field direction. The quantized energy is e = (h/2p)gB_z. The quantity g is the magnetogyric ratio and B_z is the magnetic field! A typical magnitude for e is 1.2 x 10^-24 J in a 10 Tesla magnet. Assuming this value for the energy gap between 0 and 1 write an expression for the molecular partition function, q for the two level spin system.

A. Calculate the population difference between level 0 and level 1 at 300 K.

B. How would you change the temperature to increase the population difference in this spin system?

C. Calculate the average energy of the system at 300 K.

3.

Calculate the work of an isothermal reversible expansion for a hard sphere gas given that the molecular partition function is