Unformatted text preview: fectly (as if there were NO intermolecular interactions). e) The change in energy with volume at constant temperature is equal to 0 for ideal gases. True statement. The molar volume of a pure substance follows the Gibbs Phase Rule, which indicates that Um is only a function of two intensive variables. Hence, we would write Um(Vm,T) to indicate that the molar energy is for a pure substance a function of Vm and T. Alternatively, we can write that U is a function of V and T or U(V,T). For ideal gases, the molar energy is only a function of T (no intermolecular interactions). Hence, the energy is only a function of the temperature [(∂Um/∂Vm)T = 0 or (∂U/∂V)T = 0] f) Go in the lab and add three 2 mg nuggets of gold, one 5 mg nugget of silver, a fraction of a tea spoon of table salt, a droplet of oil to a gallon of water in a two gallon bucket and close the lid. The bucket contains five phases. True statement: gold is one phase, silver is one phase, table salt dissolves in water and forms with water one liquid phase, oil does not dissolve in water (or very little does) and forms its own separate liquid phase, the air above the liquid forms the last phase). Question 4: (5 points) Which of the following statements is incorrect? a) A homogeneous solution containing multiple components is a one phase system. This is true and is the definition of a phase (regardless of the number of components) b) The state property one refers to when discussing the frequency and strength of collisions between gas molecules and the walls of the vessel containing the gas is the pressure. This is true and is how we calculate the pressure in the kinetic theory of gases. c) To obtain the root mean squared speed of gas molecules in m/s, it is necessary to use the temperature in kelvin, the molar mass in g/mol and R = 8.3145 J/mol.K. This is incorrect. To measure the speed of molecules in SI units (i.e. in m/s), we need to make sure all quantities involved (M, T and R) are also in SI units. Hence, R should be in J/K.mol, T in K and M in kg/mol). d) For an ideal gas, the quantity α is equal to 1/T. True statement. Indeed, α = (1/V) (∂V/∂T)P = (1/V) x (∂[nRT/P]/∂T)P = (1/V) x (nR/P) = 1/T e) Euler’s chain...
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 Spring '07
 AREsker
 Physical chemistry, Thermodynamics, pH

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