Fall 07 Mid Term 3 MW - Midterm III Chemistry 400 Form A...

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Midterm III Chemistry 400 Name ____________________________________________ Form A Please use scantron to mark your answers for questions 13 through 25 (3 points each) and show all your work for questions 1 through 12. 1. Use Hess's Law to calculate the enthalpy change for the reaction (6 points) NO( g ) + O( g ) NO 2 ( g ) from the following data: NO(g) + O 3 ( g ) NO 2 ( g ) + O 2 ( g ) Δ H = -198.9 kJ O 3 ( g ) 1.5O 2 ( g ) Δ H = -142.3 kJ O 2 ( g ) 2O( g ) Δ H = 495.0 kJ
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2. A piece of metal is heated by placing it in hot oil. It is removed from the hot oil and dropped into a beaker of cold water. Does heat transfer from the metal to the cold water or from the cold water to the metal? What is the sign of the enthalpy change for the metal? (4 points) 3. Calculate q when 15.0 gm of ice melted at 0 0 C and the melted water is heated from 0 0 C to 100 0 C. Heat fusion of ice = 334 J/g and specific heat capacity of water = 4.184 J/g/K. (8 points)
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4. Consider the following reaction: Al 2 O 3 (s) barb2right 2Al (s) + 3/2 O 2 (g) Δ H rxn = 1676 kJ How many grams of aluminum can form when 2.000 x 10 3 kJ of heat is transferred? (6 points) 5. What is the speed of an electron that has a de Broglie wave length of 150. nm? (electron mass = 9.11 x 10 -31 kg; Planck constant = 6.626 x 10 -34 kg.m 2 /s) (6 points)
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