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Unformatted text preview: Examination Version 001 December 16th, 2005 1. A solution of 5.0 g of an unknown solute dissolved in exactly 100 g of water is heated slowly at a constant pressure of 1 atm. It is observed to boil at 100.421 °C. Estimate the molar mass of the solute in g · mol –1 . Data: K b = 0.512 °C · kg-H 2 O · (mol solute) –1 . A. 22 B. 30 C. 60 D. 70 E. 96 2. During the manufacture of uranium fuels, solid uranium tetrafluoride (UF 4 ) reacts with gaseous fluorine (F 2 ) to form gaseous uranium hexafluoride (UF 6 ) by the following equilibrium reac- tion: UF 4 (s) + F 2 (g) UF 6 (g) The reaction is endothermic. Exactly 1 mol of F 2 (g) and 1.2 mol UF 4 (s) is placed in a 10 L (constant volume) container and the reaction is allowed to proceed to equilibrium. At 250 °C the mole fraction of UF 6 (g) is 0.6 at equilibrium. Consider the following statements about the reaction: A. At constant temperature, the total pressure in the vessel increases as the reaction proceeds to equilibrium; B. Since the total pressure at equilibrium is not given, the numerical value of K p for the above reaction at 250 °C cannot be calculated; C. The mole fraction of UF 6 (g) at equilibrium in the container would increase if the initial fluorine concentration was halved; D. The mole fraction of UF 6 (g) at equilibrium in the container would increase if the initial UF 4 (s) was doubled; E. The mole fraction of UF 6 (g) at equilibrium in the container would increase if the reaction temperature was increased. The single correct or single incorrect statement is: A. B. C. D. E. 3. You are given the following equilibrium reaction, CO (g) + H 2 O (g) CO 2 (g) + H 2 (g) A reactor initially contains only CO and H 2 O, each at a concentration of 0.100 M. What will be the concentration (in mol · L –1...
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- Spring '08
- Chemistry, Chemical reaction, Kc, g·mol–1