Researchers measure the compressibility factor of methane at two temperatures
CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
Researchers measure the compressibility factor Z of methane at two temperatures.
Temperature A: 280 K
Temperature B: 380 K
For each temperature, Z is measured at pressures of 1, 10, 50, 100, and 200 atm. The results are shown in the table.
P (atm)
Z at 280 K
Z at 380 K
1
0.996
1.002
10
0.912
0.975
50
0.790
0.893
100
0.912
1.032
200
1.247
1.321
(a) Using only the data, identify the pressure range at each temperature where intermolecular attractions are the dominant cause of non-ideality. State the evidence from the table that supports your identification.
(b) For 380 K, determine the approximate pressure at which the sign of the deviation from ideality changes. Explain your method clearly.
(c) Compare the magnitude of volume-dominated deviation at 200 atm for the two temperatures and provide a molecular interpretation for the difference.
(d) Suppose engineers need methane to behave as ideally as possible at 50 atm. Recommend which of the two temperatures should be chosen and defend your recommendation with quantitative and conceptual arguments.