Practice quiz thermodynamics 20 points
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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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Practice quiz thermodynamics 20 points

PRACTICE QUIZ THERMODYNAMICS(20 points)


  • 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)?


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