Chem340 Physical Chemistry for Biochemists Dr. Yoshitaka Ishii Homework 2 (Rev1) Due Date Jan 26, 2011 1. ( a ) Calculate the molar volume, temperature, and pressure of N 2 at the critical point using van der Waals parameters a and b (see Table 1.1 below). (b) Obtain the density of N 2 at the critical point, and compare it with that of liquid N 2 (~0.8 g/mL). Assume that the molar mass of N 2 is 28.0 gmol-1 . 2. Assume T C ~ 2T m . Answer which of He, Ar, CO 2 , N 2 , H 2 O have the highest and lowest T m based on Tc estimated from Table 1.1. Give reasoning with calculations of T m . 3. Calculate the pressures for (a) He and (b) H 2 O from van der Waals equation when the molar volume is 0.6 L and T = 310 K. 4. The critical constants of ethane are T c = 309.15 K, V mc =112.7 cm 3 mol-1 . (a) Calculate the van der Waals parameters of the gas. (b) Calculate the critical pressure P c . (c) Estimate the radius of the molecule. 5.
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