find molar volume of oxygen?

Question

Using the law of corresponding states, calculate the molar volume of oxygen gas at 126 K and 21 atm.

Answer 1

First, I will use the ideal gas law. However, the ideal gas law is normally only really valid at low pressures. This is pretty high pressure.

PV=nRT

where P =21 atm
T =136K
n=1 mole
R = 8.3 J/mole-K

V = 0.492 L

Answer 2

I have answered a similar question. It is the same as an ideal gaz (0.492L)

Answer 3

PV=nRT


V=nRT/P
(16g)(0.0821)(126K)/21
V=7.88L


n(moles)=PV/RT

(21atm)(7.88L) / (0.0821)(126)=
n=15.9moles

dont take my answer as correct though. this question seemed to be pretty tricky. hopefully someone may have a better answer