Thermodynamics, Statistical Physics, and Quantum Mechanics

10 PROBLEMS

for the atoms. The size of the hole is muchsmaller than the size of the

container and much smaller than the mean free path of the atoms.

Calculate the number of atoms striking the wall of the container per

unit area per unit time. (Express your answer in terms of the mean

velocity of the atoms.)

What is the ratio of the average kinetic energy of atoms leaving the

container to the average kinetic energy of atoms initially occupying

the container? Assume that there is no flow back to the container.

Give aqualitativeargument and computethisratio.

How much heat must you transfer to/from the container to keep the

temperature of the gas constant?

a)

b)

c)

4.15 Surface Contamination (Wisconsin-Madison)

A surface scientist wishes to keep an exposed surface “clean” ad-

sorbed monolayer) for an experiment lasting for times h at a temper-

ature Estimate the needed data and calculate a value for the

required background pressure in the apparatus if each incident molecule

sticks to the surface.

4.16 Bell Jar (Moscow Phys-Tech)

A vessel with a small hole of diameter in it is placed inside a high-vacuum
chamber (see FigureP.4.16). Thepressure is so low that the mean free path
The temperature of the gas in the chamber is and the pressure
is The temperature in thevessel iskept at a constant What
is the pressure inside the vessel whensteady state is reached?