The table below lists experimentally determined values of the compressibility factor Z for argon at 400 K.
Pressure (atm) → 0.50 5.0 15 30 40
Z → 0.995 0.970 1.010 1.080 1.120
(a) Using the data, determine the pressure (to the nearest atm) at which argon is expected to behave most ideally at 400 K. Show any interpolation or reasoning used to obtain your estimate.
(b) Calculate the percent deviation of the measured PV product from the ideal value nRT at 40 atm. Express your answer to three significant figures.