Asked by Anna

Use the van der Waals equation of state to calculate the pressure of 3.60 mol of NH3 at 489 K in a 4.50-L vessel. Van der Waals constants can be found here.
P=
Use the ideal gas equation to calculate the pressure under the same conditions.
P=

I have tried absolutely everything! Thank you for your help!
Answered by DrBob222
What's the problem? Isn't it just a matter of plugging in the numbers and turning the crank?
Answered by Anna
That's the problem. I was able to get the second part but cannot figure out the top. I have
(P + 2.6688)(4.5 - 0.13356) = 144.453
4.366 P - 11.653 = 144.453
P = 35.755 atm

but that isn't right.
Answered by DrBob222
My book doesn't list a and b for NH3. If you will post your work I will find the error.
Answered by Rune
Without the specific gas constants a and b you won't be able to do use Van der Waals (non-ideal) gas law.

P= ((nRT)/(V-nb))-a(n^2/V^2) <-- modified to get Pressure
____________________________

The ideal gas law is PV=nRT.
P is pressure (atm)
V is Volume (in Liters)
n is the number of moles
R is a constant (0.08206)
T is Temperature (in kelvin)

P= [(3.60mol NH3)(498K)(0.08206)]/(4.50L)
P= 144.4584/4.50
P= 32.1 atm
Remember to use Sig Figs if required.
Answered by Brayan Armi
Are you guys still alive?
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