- #1
Boltzano
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- 0
Homework Statement
Derive an equation how one can calculate concentration by measuring pressure change in a known volume.
Known data:
Pressure change dp/dt in a known volume V, volumetric flow rate F, total pressure p and temperature T.
Homework Equations
Probably ideal gas law pV=NkT and mass volume rate (throughput) Q=Fp=d(pV)/dt
The Attempt at a Solution
Not really sure how to solve this since this was not an textbook question but actual measurment so I'm not sure about the needed equations. But I would start:
d(pV)/dt=V*dp/dt=Q=Fp (since V is constant)
=> V*dp/dt=(Nkt/p)*(dp/dt)=Fp
=>N=(Fp^2/kT)*(dt/dp)
But doing so I end up with number of molecules and not concentration. This could easily be solved by dividing with known volume V but for some reason I won't get right numerical concentration (in measurments computer program calculated the concentration automatically from known data).