Argon gas fills a chamber at and

PHYSICS · Multi-part · Fermi University Physics · Thermal, Statistical & Complex Systems · Kinetic theory and transport in gases · Kinetic theory and transport in gases

Thermal Physics, Ch Collisions, mean free path and transport in gases

Problem

Argon gas fills a chamber at

p = 2.0\,\mathrm{kPa}

and

T = 300\,\mathrm{K}

. Treat it as an ideal gas of hard spheres of diameter

d = 0.34\,\mathrm{nm}

, with mean free path

\lambda = 1/(\sqrt2\,n\sigma)

. A classmate writes "the molecule is a disc of diameter

d

, so its collision cross-section is

\sigma = \pi d^2/4

" and obtains

\lambda = 16\,\mathrm{\mu m}

. ((a)) Calculate the correct mean free path. ((b)) By what factor is the classmate's value too large?

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