HERE ISTHE HOMEWORK QUESTION (L2bar/mol2) (L/mol) Acetylene 4.448 OR 4.39ATM 0.0

Question

HERE ISTHE HOMEWORK QUESTION

               (L2bar/mol2)          (L/mol)
Acetylene          4.448 OR 4.39ATM                          0.05136

Calculate the difference in pressure (in atm) when 100.0g ofacetylene acts as an ideal gas versus as a real gas in a 100L tankat a temperature of 1000K.

HERE WASHELP FROM AN EARLIER POST:

1) Change100.0g C2H2 to moles (n)
2) Calculate the ideal pressure using the IdealGas Law:
PV = nRT, P = nRT/V
3) Calculate the real pressure using the Van derWaals Equation. You can find the equation here:
http://hyperphysics.phy-astr.gsu.edu/Hbase/Kinetic/waal.html
Constants "a" and "b" for acetylene can be found here:
http://en.wikipedia.org/wiki/Van_der_Waals_constants_(data_page)
The difference between P(ideal) and P(real) can be found bysubtracting the smaller from the larger one.
[Be prepared to spend some time on this problem]

HERE IS MY HOMEWORK:

I have been trying the real gases homework for hours and amcompletely stuck. This is what I have been attempting to make work.First I found the moles then plugged in all the othervariables.

100gC2H2/26.0373g/mol=3.84mol C2H2=n

P=nRT/(V-nb)-an^2/V^2

   P=   n     R    T /(V - n   b)   - a   n^2 / V^2

319.49=3.84x8.3145x1000/(100-3.84x.05136)-4.39x3.84^2/100^2

319.49 is not the correct answer and I have only confused myselffurther and further trying to understand this. At this point I amjust pushing buttons on my calculator hoping for a miracle. Pleaserelease me from my torture:)

319.48592180530454

Explanation / Answer

Calculate ideal gas Pressure with PV=nRT P = nRT/V n = 100 g/ 26.04 g/mol = 3.84 mol R = .0821 T = 1000 K V = 100 L P = (3.84 x .0821 x 1000) / 100 P = 3.1541 atm (Note: you used the wrong R constant: its .0821,not 8.3145) Calculate real gas pressure P = -an^2/V^2 + nRT/(V-nb) a = 4.448 b = .05136 P = -4.448(3.84^2) / (100^2) + (3.84)(.0821)(1000) /(100-(3.84x.05136) P = 3.1523 atm Difference between ideal and real: 3.1541 - 3.1523 = .00174 atm or1.32 mmhg

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