# Exam 2 Problems and Answers - Problem#1 1.000 mol of...

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Problem #1 1.000 mol of toluene and 2.000 mol of benzene, initially separated, are placed into an isolated container at 298 K and 1.000 atm pressure. What is the entropy change of the universe when these liquids are mixed within the container? Assume ideal behavior. ΔS universe = _____ +15.88 _________ J/K Problem #2 Two volatile liquids form an ideal mixture. The normal boiling of pure component 1 is 350.0K and the normal boiling of pure component 2 is 450.0K. Assume Trouton’s rule (ΔS vap0 = 88 J/K . mol) and the Clausius-Clapeyron relation hold for both materials. a) What is the constituency of the mixture of liquids 1 and 2 that has a normal boiling point of 400.0K? Give the mole fraction of component 1 in this liquid. X 1 = ____ 0.2103 _____________ b) What is the constituency of the vapor in equilibrium with the mixture described in part a) at its normal boiling point? Give the mole fraction of component 1 in the equilibrium vapor. Y 1 = ____ 0.7897 _____________ Problem #3 Consider one mole of an ideal monoatomic gas (C V /n = (3/2)R) at a temperature of 100 o C and a pressure of 2.00 atm. Please relate the properties of the gas at this temperature and pressure to the properties of the same gas at STP: a) What is the relative number density of the gas, i.e., what is ρ/ρ STP ? ρ/ρ STP = (273/373)(2.00/1.00) = 1.46381 b) What is the relative mean speed of the gas, i.e., what is <c>/<c> STP , of the gas <c>/<c> STP = (373/273) 1/2 = 1.16889 c) What is the relative collision frequency per unit volume of the gas, i.e., what is (Z 11 )/(Z 11 ) STP ? (Z 11 )/(Z 11 ) STP = (1.16889)(1.46381) 2 d) What is the relative collision frequency per molecule of the gas, i.e., what is (Z 1 )/(Z 1 ) STP ? (Z 1 )/(Z 1 ) STP = (1.16889)(1.46381) e) What is the relative mean free path of the gas, i.e., what is, λ/λ STP , of the gas? λ/λ STP = (1.46381) -1 f) What is the relative diffusion coefficient of the gas, i.e., what is, D/D STP , of the gas? D/D STP = (1.16889)(1.46381) -1 g) What is the relative viscosity coefficient of the gas, i.e., what is, η/η STP , of the gas? η/η STP = (1.16889) h) What is the relative thermal conductivity of the gas, i.e., what is, κ/κ STP , of the gas? κ/κ STP = (1.16889) Problem #4 Consider the following thermodynamic data at 298 K: ΔG f o [Br 2 (gas) ] = 3.110 kJ/mol ΔG f o [Br (gas) ] = 82.396 kJ/mol ΔH f o [Br 2 (gas) )] = 30.907 kJ/mol ΔH f o [Br (gas) ] = 111.88 kJ/mol (A Note on Percent Dissociation: If 1.00 mole of Br 2 (gas) is introduced into a reactor and 0.500 mole of this gas dissociates into 1.00 mole of Br Atoms, the percent dissociation is 50%. Since both Br 2 and Br are treated as ideal gases, the volume of this reactor must increase by a factor of

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1.50 to maintain constant pressure. All parts of this problem treat the dissociation process at constant temperature and pressure.) a) What is the equilibrium constant for the reaction: Br 2 (gas) 2 Br (gas) , at 298K? K = 4.575 x 10
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Exam 2 Problems and Answers - Problem#1 1.000 mol of...

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