Unformatted text preview: e property by an intensive property is extensive. The product or the ration of two intensive properties is intensive. This implies the following: P/(ρT) Intensive (VT)/(Vm) Extensive (nT)/(PVm) Extensive PV/nT Intensive ΔU/ΔT Extensive (1/V) (∂V/∂T)P Intensive Hence, there are three intensive properties and three extensive properties. Choice “c” is correct. Which of the following statement is true regarding this list of six quantities? a) There are five extensive quantities and one intensive quantity b) There are four extensive quantities and two intensive quantities c) There are the same numbers of extensive quantities and intensive quantities d) There are four intensive quantities 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 molecules in an ideal gas is directly proportional to the temperature of the gas. 2
This statement is incorrect. 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 1/2
temperature and kB is the 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 (not Temperature itself). 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” per...
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 Spring '07
 AREsker
 Physical chemistry, Thermodynamics, pH

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