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Joined: 08 Jun 2017
Posts: 1

# Van der Waals Questions/Need help

Hello!

I am using the van der waals calculator to check my calculations but I seem to be getting very different numbers and im not sure why.

I am using this equation (P + a(n/v)^2)(v-nb) = nRT

My units are pressure in atm, volume in Liters and temp in kelvin. Im using R as atm L mol-1 k-1 . I am trying to isolate to solve for moles in a given container.

My Pressure is 3600 psi ~ 244.9655 atm
My internal volume is 41.9 L
My temperature is 294.2611111 K
The gas i am correcting for is oxygen.. My a is 1.362652 atm L^2 mol^-2 and my b is 0.03186 L/mol.

Calculating this out and solving for n i get 462.324 moles however the webqc calculator gives me 321.458....

I'm not sure if I am running into a conversion error or a simple mathematical error but if anyone could help that would be awesome!
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