Determine the mass of an ethane gas stored in a 25 ft3 tank at 250 F, 440 lbf/in.2 using the compressibility chart. Estimate the error (%) if the ideal gas model is used.
Tr = ( 250 + 460 ) / 549.7 = 1.29 and Pr = 440/708 = 0.621
⇒ Z = 0.9
m = PV/ZRT = 440 × 144 × 25 / (51.38 × 710 × 0.9)
= 48.25 lbm
Ideal gas Z = 1
⇒ m = 43.21 lbm 10% error
