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Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: diamie24 on October 01, 2014, 07:37:45 PM

Title: Need help starting a problem!
Post by: diamie24 on October 01, 2014, 07:37:45 PM
Hey everyone! I need help starting this problem.

How many times less frequently than at a pressure of 760 Torr (1 atm) at a temperature 25 C would an oxygen molecule collide with another oxygen molecule in a container of only oxygen that is at a pressure equal to 100 miles above the earth ( 7.9x10-8 Torr) at 10 K (-263.15 C)? What is the mean free path (distance) between collisions?

Title: Re: Need help starting a problem!
Post by: mjc123 on October 02, 2014, 05:44:20 AM
Look up "collision frequency" and "mean free path" in any standard physical chemistry textbook (I just did it with Atkins) or online, and you should quickly find equations that will give you the answer to your questions (assuming oxygen is an ideal gas).
Title: Re: Need help starting a problem!
Post by: diamie24 on October 02, 2014, 08:50:04 AM
I looked up the mean free path equation.  However, there is no diameter given in the problem for the d^2 value that is needed in order to solve the mean free path equation.
Title: Re: Need help starting a problem!
Post by: Corribus on October 02, 2014, 09:16:26 AM
So estimate it. What basic property of O2, that you can easily look up, could be used as an approximation of the size of the molecule?
Title: Re: Need help starting a problem!
Post by: diamie24 on October 02, 2014, 04:08:49 PM
The molar mass and the density of O2?