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Name: Doug
Status: other
Grade: other
Location: NY
Country: N/A
Date: April 2006
Question:
Based on the paper found at :

http://dbhs.wvusd.k12.ca.us/webdocs/Chem-History/Loschmidt-1865.html

Given the size of an air molecule as described in this paper, what would be the comparative size of a nitrogen molecule? I am trying to simply quantify the theoretical difference for a comparison between the leak rate of air from a tire inflated with air to 30 psig and the same tire inflated with nitrogen to 30psig.


Replies:
Remember that air is already 80 volume percent nitrogen, so the leak rate between air and pure nitrogen is not very different. In addition at pressures of the order of 30 psig all gasses obey the ideal gas law P*V = n*R*T so there is little gas-to-gas differences except for Helium which can diffuse into the rubber. FYI I am told that race cars use nitrogen instead of air to prevent oxidation of the rubber in the tires at the high operating temperatures in a race car tire. Makes chemical sense but I do not know that it is the case first hand.

Vince Calder


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