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CalebB-M
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Homework Statement
The density of air is given as .001g/cm^-3 and the density of liquid air 1g/cm^-3
A.) Estimate the number of air molecules per cm^3
B.) Estimate the Mass of a single molecule.
C.) Estimate the average distance L an air molecule should travel between collisions at normal temperature and pressure (20c and 1atm) "mean free path"
D.) Estimate at what pressure P in normal atmosphere a vacuum system should be operated under so that L = 1 meter.
That is all given data.
Homework Equations
None were given at all in the book or referenced in the Feynman lectures themselves. This is what caused most of my confusion as I simply don't know some of what is asked.
The Attempt at a Solution
A.) I used the average molar mass of air and 15*1avagadros number to estimate the number of molecules in the 1cm^3. But my answer was 2*10^19 wheras the book gives the answer as 10^19, I am not sure where I could have gotten my answer off by a factor of two. .001g/cm^-3 * (6.022*10^23)/(28g/mole) = aprox 2.15*10^19
B.) This one confused me as i used it to calculate the first one, but still that lead to me getting 4*10^-23 g simply dividing the .001g/cm^3 by #of atoms from a per cm^3 the cm^3 cancel leaving .001g/(#of atoms)
C.) This one I'm confused on how to even start. I literally have lost it I tried thinking about how I could get a unit of length from the values I had been given, but I haven't remotely begun to understand it. I tried imagining that i had a 1cm^3 box and there are #number of atoms whirling around randomly in the box. But i still have hit a road block and could use some pointers.
D.) Havent gotten to this problem yet.
Notes:
The book exercises for the Feynman lectures has really challenging problems, but studying all by myself and not within a classroom environment makes it impossible to ask questions or get clarification. I am alone in this endeavor, maybe someone on the forum could do them with me?