# HW1 - experimental value. 3. As we discussed in class the...

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Chemistry 252 Homework 1. Due Wed. Jan 28 1. Use the following data for unknown gas at 300 K to determine the molecular mass of the gas P (bar): 0.10000 0.5000 1.000 2.000 ρ (g/L): 0.17771 0.8909 1.796 3.652 2. In this problem we will test the accuracy of Van der Waals equation for water around its critical point. A book gives the following expressions for critical temperature, pressure and volume: P c = a 27 b 2 (1) T c = 8 a 27 bR (2) V c = 3 b (3) Table 16.5 in the book gives the following values for the critical point of water: T c = 647K, P c = 220.5 bar, V c = 0.05595 L/mol. Use eq. (3) to find b, then substitute the value of b into eq. (1) to find a. If Van der Waals equation of state was accurate the equation (2) would be satisfied. Plug in your valuies into equation (2) to obtain a Van der Waals critical temperature and compare it to the
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Unformatted text preview: experimental value. 3. As we discussed in class the V-d-W equation can be written in term of reduced quantities P R = P / P c , V R = V / V c , T R = T / T C , as: P R + 3 V R 2 V R − 1 3 = 8 3 T R . (4) Verify by substituting eq-s. (1-3) into (4) that this equation is the same as the normal V-d-W equation. 4. We discussed in class that the V-d-W constant b has the meaning of volume excluded by molecules. If we assume that molecules are spheres the volume taken by 1 molecule should be about d 3 , where d is the diameter of the molecule. Use the table value, b = 3.8 10-5 m 3 /mol, for Kr to estimate its diameter d . Does this number make sense?...
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## This document was uploaded on 06/23/2009.

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