- #1
larsb
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Homework Statement
I would like to know how to calculate how much moles of gas I have in the following in a cylinder with a certain volume and pressure.
The gas in the cylinder is a mixture of air, with added oxygen and helium, the mixture is 18% Oxygen, 36,6% Nitrogen, 45% Helium and 0,4% Argon. The cylinder is 24 liters big, the pressure in the cylinder is 200bar.
I can calculate the a and b values for the gas mixture.
P = 200 bar
V = 24 L
T = 293,15 K
R = 0,083145 L bar K-1 mol -1
a = 0,8746 L2bar mol-2
b = 0,0388 L mol-1
Homework Equations
PV = nRT ( ideal gas law)
P = nRT (V-nb)-1 - n2a V-2
The Attempt at a Solution
According to the ideal gas law this should be 196,93 moles, but that is not right, since if I use the Vanderwaals equation I end up at a pressure of 234,6 bar to accommodate 196,93 moles of this gasmixture.
Using the Vanderwaals equation I can't calculate the exact number of moles, this is where is end up:
200 = 24,37n (24 - 0,0388n)-1 - 0,00152n2
So please enlighten me, how can I proceed to calculate the value for n?