Thermodynamics, Statistical Physics, and Quantum Mechanics

(^102) SOLUTIONS
For an estimate we can assumethat the adsorbed molecules are closely
packed and that the number of adsorption sites on a surface of area A is
where d is the average diameter of the adsorbed atoms, and we take
The total number of adsorptionsites mayactually besmaller(thesedata
can be obtainedfrom thetime tocreate one monolayer at lowerpressure).
We may write
or, for 1 of surface,
Using the averagevelocity from Problem4.13 at Kgives
and
Thus,
So, we will have to maintaina pressure better than Torr, which can
be quite a technicalchallenge. Infact, at such lowpressures the resid-
ual gas composition is somewhatdifferent from roomair,since it may be
moredifficult to pumpgasessuch as and He.Therefore, (S.4.15.3) and
(S.4.15.5) are only order-of-magnitude estimates.
4.1 6 Bell Jar (Moscow Phys-Tech)
The pressureinside thevessel
just