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Unformatted text preview: uantities and two extensive quantities e) There are five intensive quantities and one extensive quantity Question 3: (5 points) Which of the following statements is incorrect? a) Gases behave ideally when the molar volume is very large. True statement accounting for the fact that the larger the molar volume, the larger the average distance between molecules, the smaller the magnitude of the intermolecular interactions, hence, the more perfect the gas behavior. 1 b) The r.m.s. speed of ideal gas molecules is directly proportional to the square root of the temperature. 2
This statement is correct. Indeed, the kinetic energy of gas molecules is ½ mc , where c is the root mean squared speed and m is the molecule mass. In the kinetic theory of gases, kinetic energy of the molecules is equated to the thermal energy (3/2 kBT), where T is the absolute temperature and kB is the 1/2
Boltzmann constant. Hence, c is given by (3RT/M) , where M is the molar mass of the molecules (M = m x NAvogadro) and R is the Ideal/Perfect Gas constant (R = kB x NAvogadro). So, c is directly proportional to the square root of Temperature. 2
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c) At the critical point the following equalities are true (∂P/∂Vm)T = 0 and (∂ P/∂Vm )T = 0 True statement reflecting the fact that the critical point is the inflection point on an isotherm (T = constant in a P versus Vm plot). d) At the Boyle’s temperature, attractive and repulsive interactions balance each other. True statement. This is why at the Boyle’s temperature, the gas “behaves” perfectly (as if there were NO...
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This note was uploaded on 01/26/2014 for the course CHEM 3615 taught by Professor Aresker during the Spring '07 term at Virginia Tech.
 Spring '07
 AREsker
 Physical chemistry, pH

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