Chemistry 360 Spring 2017 Dr. Jean M. Standard April 19, Exam points

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1 Chemistry 360 pring 2017 Dr. Jean M. tandard April 19, 2017 Name Exam points Note: You must show your work on problems in order to receive full credit for any answers. You must turn in your equation sheet along with this exam in order to receive full credit for the exam. Please turn off cell phones and store them during the exam. 1.) (14 points) Consider the reaction H 2 ( g) + F 2 g ( ) 2 HF( g). At 1000 K and 10 atm, the equilibrium constant for the reaction is Determine the extent of reaction and the equilibrium partial pressure of HF if 1.0 mole of H 2 and 1.0 mole of F 2 are initially placed in the reaction vessel.

2 2.) (14 points) At 300 K, the pure vapor pressure of acetone is 229 torr and the pure vapor pressure of chloroform is 197 torr. A certain mixture is obtained by mixing 3 moles of liquid acetone and 1 mole of liquid chloroform. Assume ideal solution behavior. 2 a.) As the pressure is reduced from a large value, at what pressure does vapor first appear? b.) Determine the vapor phase mole fractions of acetone and chloroform.

3 3.) (14 points) he temperature dependence of the chemical potential for a single component system is shown below for a pressure of 1 atm. 3 µ On the diagram above, indicate the temperature at which solid-liquid equilibrium occurs (the melting point) and the temperature at which liquid-vapor equilibrium occurs (the boiling point). Now, consider what happens to the diagram above if the pressure is increased. Does the boiling point of the system increase or decrease relative to its 1 atm value? Explain your reasoning on the basis of changes in the chemical potentials. ketch the behavior of the chemical potentials as a function of temperature for a higher pressure. You may want to use the diagram above and draw in the changes in the chemical potentials for the higher pressure relative to those shown for P=1 atm, or you may draw your own.

4 4.) (15 points) rue/false, short answer, multiple choice. 4 a.) rue or False: he Clausius-Clapeyron Equation may be used to describe soild-vapor, liquid-vapor, and solid-liquid phase equilibria. b.) rue or False: he extent of reaction provides a measure of the progress of a chemical reaction from reactants to products. c.) hort answer he allows the determination of the number of independent thermodynamic variables (or degrees of freedom) available in a chemical system. d.) hort answer he is the point at which drops of liquid first appear in a twocomponent system as the pressure is increased from a small value. e.) Multiple Choice: For the graphs shown below corresponding to one-component phase diagrams, circle the one that corresponds to a situation in which the system expands upon freezing. P P (a) (b) P P (c) (d)

5 5.) (14 points) he melting point of mercury is 38.9 C at 1 bar and 19.9 C at 3540 bar. he density of liquid mercury is g/m and the density of solid mercury is g/m. Determine the molar enthalpy of fusion. [he atomic mass of Hg is g/mol.] 5

6 6 6.) (14 points) Consider the reaction CaCO 3 ( s) CaO( s) + CO 2 ( g). In the reaction, the equilibrium vapor pressure of CO 2 is measured to be atm at 700 C and atm at 1100 C. Determine the standard molar enthalpy of reaction, assuming that it is independent of temperature.

7 7 7.) (15 points) rue/false, short answer, multiple choice. a.) rue or False: A graph of Gibbs free energy versus extent of reaction exhibits a maximum corresponding to the position of chemical equilibrium. b.) rue or False: he reaction 2ClO g pressure of the system is increased (at constant ). ( ) Cl 2 O 2 ( g) is expected to shift to the left if the total c.) hort answer aw is valid for the solvent in a binary mixture. d.) hort answer wo phases exist in equilibrium along the on a phase diagram. e.) Multiple Choice: Circle the pair of compounds below that you expect would be most likely to form an ideal solution. (a) water (H 2 O) and cyclohexane (C 6 H 12 ). (b) acetone (CH 3 COCH 3 ) and acetaldehyde (CH 3 CHO). (c) 1-octanol (C 8 H 17 OH) and water (H 2 O). (d) benzene (C 6 H 6 ) and n-hexane (C 6 H 14 ).

8 8 CHE 360 PHYICA CONAN AND EQUAION R = atm mol 1 K 1 = J mol 1 K 1 = bar mol 1 K 1 1 atm = Pa = kpa = bar = 760 torr 1 bar = 10 5 Pa = 100 kpa = atm 1 atm = J; 1 bar = 100 J 1 cal = J Fundamental Equations du = d P d dh = d + dp da = d P d dg = d + dp Note: for open or reacting systems, add N µ i dn i to each of the fundamental equations. i=1

Exam 3 Solutions. ClO g. At 200 K and a total pressure of 1.0 bar, the partial pressure ratio for the chlorine-containing compounds is p ClO2

Exam 3 Solutions. ClO g. At 200 K and a total pressure of 1.0 bar, the partial pressure ratio for the chlorine-containing compounds is p ClO2 Chemistry 360 Dr. Jean M. Standard Fall 2016 Name KEY Exam 3 Solutions 1.) (14 points) Consider the gas phase decomposition of chlorine dioxide, ClO 2, ClO 2 ( g) ClO ( g) + O ( g). At 200 K and a total