O.K. Class,
Avogadro's Number, the number of mollecules in a gram molecular weight or
mole. Approximately 6.0221424 times ten to the 23th.
Grem molecular volume: the volume of space occupied by one mole of a gas at
standard temperature and pressure: 22.4142L.
Standard temperature and pressure (STP)is the approximate temperature and
presure of the atmosphere at sea level on a nice day, 273.15 degrees Kelvin
and 760 torr.
Molecular weight of Nitrogen is twice the atomic weight of Nitrogen: 2 x
14.00674 = 28.01348.
Molecular weght of Oxygen is twice the atomic weight of Oxygen: 2 x 15.9994
= 31.9988.
At STP 22.4142 litres of Oxygen weigh 31.9988 grams. 22.4142 litres of
Notrogen weigh 28.01348.
The Oxygen is denser than the Nitrogen.
Since air is a mixture of approx 80% Nitrogen and 20% Oxygen (for our
discussion we can ignore the trace gasses such as helium and argon and even
radon) it is (proportionally) more dense than the pure Nitrogen but less
dense than the pure Oxygen.
Boyle's law: At a constant temperature the amount of space occupied by a
given weight of gas is proportional to the pressure. If we igniore the
increase in size of the tire with higher pressure, you need twice as much
Nitrogen to fill your tires to 32 psi as you need to fill them to 16 psi.
Charle's Law: at a constant pressure, the amount of space occupied by a
given weight of gas is proportional to the temperature above absolute zero
( -273.15 degrees Celsius.) If your tires heat up from O Celsius to 273.15
Celsius on a fast lap, the pressure in them will double.
At 32 psi, or whatever you inflate your tires to the Nitrogen will still be
lighter (and less dense) an equal volume of air.
Anybody still wants to save money by filling his tires with Nitrogen rather
than air contact me off list: I have a bridge for sale. You can make lots
of money charging tolls into NYC. Or if you are in Canada tolls into
Detroit...
Hal
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