Calculating Mean Free Path of N2 Molecule in UHV Chamber

AI Thread Summary
To calculate the mean free path of an N2 molecule in an ultra-high-vacuum chamber at 10^-10 mbar, the formula λ=1/(√2)nσ is used, where n is the number density and σ is the collision cross-section. The pressure p can be related to number density n and temperature T using p=nkT. The collision cross-section σ is calculated as σ=πd², with d estimated around 10^-10 m. Since the temperature T is not provided, a standard reference temperature of 0°C is suggested for the calculation. This approach allows for an estimation of the mean free path in the given conditions.
albega
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Homework Statement


What is the mean free path of an N2 molecule in an ultra-high-vacuum chamber at a pressure of 10-10mbar?

Homework Equations


λ=1/(√2)nσ
number density n, collision cross-section σ
p=nkT
pressure p, temperature T
σ=πd2
d molecular diameter

The Attempt at a Solution


λ=kT/(√2)πpd2
where we know p and I can estimate d to be around 10-10m. However I am not given T, and I don't really see how I could know what it is...
 
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albega said:
However I am not given T, and I don't really see how I could know what it is.
At which point, you're free to assume a temperature. What's a good standard temperature for reference data?
 
Standard temperature, 0degc. Thanks.
 

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