CHEMISTRY · Multi-part · AP · Chemistry · Properties of Substances and Mixtures · Properties of Substances and Mixtures
Problem
For a certain diatomic gas, three isothermal compressibility curves are obtained at 250 K, 300 K, and 400 K. The following qualitative observations are recorded:
• At 250 K the Z curve shows a minimum value of 0.60 at 25 atm before rising above 1 near 120 atm.
• At 300 K the minimum is 0.80 at 20 atm and Z reaches 1 near 70 atm.
• At 400 K the curve stays between 0.95 and 1.05 over the entire range 0.1 atm – 150 atm.
(a) Explain how increasing temperature alters the depth and position of the minimum in a Z versus P curve for a real gas.
(b) Which of the three temperatures provides the widest pressure range over which the gas behaves nearly ideally? Justify your choice with reference to the observations above.
(c) Relate the trends in the three curves to the concept of critical temperature. Predict whether the critical temperature of this gas is closer to 250 K, 300 K, or 400 K, and defend your prediction.