Chemical Forums

Chemistry Forums for Students => High School Chemistry Forum => Topic started by: cherrygirl10 on April 16, 2005, 04:46:08 PM

Title: Air density
Post by: cherrygirl10 on April 16, 2005, 04:46:08 PM

What is the density of air at 108 degrees F?

Title: Re:Air density
Post by: Borek on April 16, 2005, 06:27:38 PM

For general purpose calculation you may try following approach:

Air is a mixture of 21% O2 and 79% N2 (I am leaving 1% of Ar as it don't influence the result). Assuming that it behaves like ideal gas (which you can safely do as long as you are far from high pressures and low temperatures) you may treat thhis mixture as a ONE gas with molar mass equal to weighted average of molar masees of oxygen and nitrogen - so it will be

(21*32 + 79 * 28)/100 = 28.8

Now, you know molar mass and you know that under STP 1 mole of gas has volume of 22.4 liters. Use pV = nRT to calculate volume for your temperature (or use just V/T = const) and youare almost ready - you take 'molar mass' of air and you divide it by the 1 mole volume. Pronto!

Title: Re:Air density
Post by: charco on April 16, 2005, 08:20:13 PM

Pronto???

shurely
Presto!

Title: Re:Air density
Post by: Jiro on April 16, 2005, 09:09:31 PM

Remember to convert F degrees to kalvins. Try using the van der Walls forces equation as well and compare the two results if the difference is great use the more accurate equation taking to account the van der Walls forces.