exam3fall2011f2

exam3fall2011f2 - ThirdExaminationFall2011...

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Third Examination Fall 2011 General Chemistry II R. Lopez de la Vega Name___________________________________ Bubble in the form number in the section entitled Grade or Educ in the scantron. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) If the pKa of HCHO 2 is 3.74 and the pH of an HCHO 2 /NaCHO 2 solution is 3.11, which of the following is TRUE? A) [HCHO 2 ] << [NaCHO 2 ] B) [HCHO 2 ] < [NaCHO 2 ] C) [HCHO 2 ] > [NaCHO 2 ] D) [HCHO 2 ] = [NaCHO 2 ] E) It is not possible to make a buffer of this pH from HCHO 2 and NaCHO 2 . 1) 2) Give the expression for the solubility product constant for PbCl 2 . A) [Pb 2+ ][Cl ] 2 B) [Pb 2 + ] 2 [Cl ] C) [Pb 2 + ][Cl ] 2 [PbCl 2 ] D) [PbCl 2 ] [Pb 2 + ][Cl ] 2 E) [Pb 2 + ] 2 [Cl ] [PbCl 2 ] 2) 3) A 100.0 mL sample of 0.10 M NH 3 is titrated with 0.10 M HNO 3 . Determine the pH of the solution after the addition of 200.0 mL of HNO 3 . The K b of NH 3 is 1.8 × 10 - 5 . A) 12.52 B) 12.00 C) 6.44 D) 2.00 E) 1.48 3) 4) Calculate the pH of a solution formed by mixing 250.0 mL of 0.15 M NH 4 Cl with 200.0 mL of 0.12 M NH 3 . The K b for NH 3 is 1.8 × 10 - 5 . A) 9.45 B) 4.74 C) 9.06 D) 4.55 E) 9.26 4) 5) Calculate Δ rxn for the following reaction. The S° for each species is shown below the reaction. C 2 H 2 (g) + H 2 (g) C 2 H 4 (g) S°(J/mol · K) 200.9 130.7 219.3 A) +112.3 J/K B) - 112.3 J/K C) +337.1 J/K D) - 550.9 J/K E) +550.9 J/K 5) B 1
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6) Determine the equilibrium constant for the following reaction at 298 K. SO 3 (g) + H 2 O(g) H 2 SO 4 (l) Δ = - 90.5 kJ A) 0.964 B) 9.11 × 10 - 8 C) 4.78 × 10 11 D) 7.31 × 10 15 E) 1.37 × 10 - 16 6) 7) Consider a reaction that has a positive Δ H and a positive Δ S. Which of the following statements is TRUE? A) This reaction will be spontaneous at all temperatures. B) This reaction will be spontaneous only at high temperatures. C) This reaction will be nonspontaneous at all temperatures.
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This note was uploaded on 12/17/2011 for the course CHM 1046 taught by Professor Staff during the Fall '08 term at FIU.

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exam3fall2011f2 - ThirdExaminationFall2011...

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