# PRACTICE QUIZ THERMODYNAMICS (20 points) - PowerPoint PPT Presentation

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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)

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## 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):

• TFa. Endothermic reactions which becomemore ordered are never spontaneous.

• TFb. A system at equilibrium cannot performany 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)?