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## Homework Statement

I'm taking an online PChem course where the instructor throws out

Z = 3Vr/(3Vr – 1) – 9/(8 VrTr); where Vr is the reduced molar volume.

2. Homework Equations

2. Homework Equations

{P + a/Vm^2}{Vm – b} = RT; where Vm is the molar volume

Tc = 8a/27Rb ; Vc = 3b ; Pc = a/27b^2

3. The Attempt at a Solution

3. The Attempt at a Solution

Start with

(Pr + 3/Vr^2)( Vr – 1/3) = (8/3)Tr

Then

Pr = {8 Tr/(3Vr – 1) - 3/ Vr^2}

and

Z = PrVr/RTr = {8 Tr/(3Vr – 1) - 3/ Vr^2} Vr/RTr

gives

Z = {8 Vr/R(3Vr – 1) - 3/R VrTr}

I can’t figure out where to go next without chasing my tail with a’s and b’s to get the R to go away and give me the correct coefficients in the rhs of the eq. Help!