Exam_Final_practice_2010

Exam_Final_practice_2010 - CHEM 222, Fall 2009 (Final Exam;...

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CHEM 222, Fall 2009 (Final Exam; total 100%) You have 50 min in which to take this exam. It is a closed book exam; only calculators are allowed. Attn! Show your work to receive credit from each problem. Physical Constants (not all need to be used) (see also Tables attached to this exam book; not all may be needed) c = 2.998 × 10 8 m/s h = 6.626 × 10 -34 J × s J = N m = kg m 2 /s 2 1 eV = 1.6022 × 10 -19 J mass of an electron, 9.11 × 10 -28 g
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Problem # 1 (20 pts): 100 mL of 0.100 M Fe 2+ was titrated with 0.100 M Ce 4+ in 1.00 M HClO 4 . Formal potentials for Fe 3+ /Fe 2+ and Ce 4+ /Ce 3+ are equal to standard potentials, and are 0.771 V and 1.61. (1) What is the potential at the equivalence point? (2) Sketch the titration curve (potential versus titration volume in the full fraction range) for this reaction. (3) Prove that the “x = 0” approximation is valid after 50 mL of titrant was added. 2
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Problem # 1 (15 pts) The figure in Harris shows molecular orbital structure of formaldehyde (Harris p.405). (A) Explain the HOMO and LUMO acronyms. (B) Assuming the transition occurs between HOMO and LUMO, explain why the color of a formaldehyde solution is not green-yellow but the solution of formaldehyde is colorless? 3
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Problem # 2 Calculate the pH of the following solutions: (a) A 0.250 M solution of acetic acid containing 0.250 M of sodium acetate upon addition of 10.0 mL of 0.10 M HCl. The volume of solution to which the 10.0 mL of 0.10 M HCl was added was 1000 mL (pK a = 4.76). (b) 1.0×10 -8 M solution of NaOH in water. 4
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Problem # 3 (a) Calculate the de Broglie wavelength of an electron with a velocity of 10.00 x 10 6 m/s. (b) Using the de Broglie equation, calculate the mass of a photon at λ = 500 nm at the velocity of a photon equal to c (c = speed of light, for constants, see 1 st page of this exam book). 5
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Problem # 4 (a) Explain the meaning of the “Limiting current” in the plot below. (b) What is the origin of the oscillations shown on this plot? 6 DC polarogram of a Cd 2+ salt in a HCl supporting electrolyte.
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Calculate free pCa in 100 ml of solution of 0.100 M Ca 2+ at pH = 10 after adding 100 ml of 0.100 M EDTA; K f = 5.0 × 10 10 . At pH
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Exam_Final_practice_2010 - CHEM 222, Fall 2009 (Final Exam;...

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