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PRACTICE QUIZ THERMODYNAMICS (20 points). 1a. (2 points) D G rxn for: 2 SO 3 (g) 2 SO 2 (g) + O 2 (g) is 139.6 kJ. If D G f for SO 2 (g) is -300.1 kJ/mole, calculate D G f for SO 3 (g)?
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1a. (2 points) DGrxn for: • 2 SO3(g) 2 SO2(g) + O2(g) is 139.6 kJ. • If DGf for SO2(g) is -300.1 kJ/mole, calculate DGf for SO3(g)? • b. (1 point) Is the formation of SO3 gas from SO2 gas and O2 gas spontaneous at 25 ºC and 1 atm pressure? • c. (1 point) What is the maximum work that could be performed by either of the above reactions?
2. (3 points) Give the expected sign on DS for the following processes: • Process DS sign • a. CaSO4(s) CaO(s) + SO3(g) _______ • b. Ag+(aq) + Cl-(aq) AgCl(s) _______ • c. I2(g) I2(s) _______ • 3. (2 points) Circle T (True) or F (False): • T F a. Endothermic reactions which become more ordered are never spontaneous. • T F b. A system at equilibrium cannot perform any work.
4. (2 points) For the reaction: • 5 Fe3++ Mn2++ 4 H2O MnO4-+8 H+ + 5 Fe2+ • Kc = 1.0 x 10-62 Given DG = -2.3 RT log Kc, what is the sign of DG for this reaction? • 5. (2 points) 1.0 mole of SO2(g) and 1.0 mole of O2(g) are mixed together in a 1.0 L flask. As SO2 and O2 react to form SO3 and proceed toward equilibrium, how does the value of the free energy change?
6. (3 points) The process: • benzene(s) benzene(l) • is spontaneous at temperatures above 5 ºC and is spontaneous in the opposite direction at temperatures below 5 ºC. • a. Explain in terms of DH, DS, and DG why the direction of the spontaneous process depends on the temperature. • b. What does the temperature 5 ºC represent for benzene? • c. What is DG for the above process at 5 ºC?
7. (4 points) For the reaction: • 3 NO2(g) + H2O(l) 2 HNO3(l) + NO(g) • the following information is given at 25oC and 1 atm: • DGrxn = + 8.4 kJ • DHf (kJ/mole): • + 34.0 for NO2(g); • -286.9 for H2O(l); • -173.9 for HNO3(l); • + 90.7 for NO(g) • Calculate DS for the reaction (DSrxn)?