exam3fall2011f5

exam3fall2011f5 - Third Examination Fall 2011 Form V...

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Unformatted text preview: Third Examination Fall 2011 Form V 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) A ligand is a molecule or ion that acts as a A) Lewis acid B) Bronsted-Lowry base C) Lewis base D) Bronsted-Lowry acid E) none of the above 1) 2) Which of the following relationships is correct at constant T and P? A) ΔG is proportional to -ΔSuniv B) ΔG > 0 represents a spontaneous process C) ΔG > 0 represents an increase in kinetic energy D) ΔG < 0 represents a nonspontaneous process E) All of the above are correct 2) 3) What is the pH of a solution made by mixing 40.00 mL of 0.100 M HCl with 25.00 mL of 0.100 M KOH? Assume that the volumes of the solutions are additive. A) 13.36 B) 10.00 C) 0.64 D) 1.64 E) 12.36 3) 4) Which of the following acids (listed with Ka values) and their conjugate base would form a buffer with a pH of 2.34? A) HClO2, Ka = 1.1 x 10-2 4) B) HF, Ka = 3.5 x 10-4 C) HC7H5O2, Ka = 6.5 x 10-5 D) HCN, Ka = 4.9 x 10-10 E) HClO, Ka = 2.9 x 10-8 5) Calculate ΔS°rxn for the following reaction. The S° for each species is shown below the reaction. S°(J/mol·K) A) -550.9 J/K C2H2(g) + H2(g) → C2H4(g) 200.9 130.7 219.3 B) +550.9 J/K C) +337.1 J/K D) +112.3 J/K E) -112.3 J/K 6) Estimate ΔG°rxn for the following reaction at 775 K. 2 Hg(g) + O 2(g) → 2 HgO(s) A) -625 kJ 5) B) +17 kJ 6) ΔH°= -304.2 kJ; ΔS°= -414.2 J/K C) -181 kJ E‐1 D) +321 kJ E) -110 kJ Form V 7) Determine the molar solubility of PbSO4 in pure water. Ksp (PbSO4) = 1.82 × 10-8. A) 4.48 × 10-4 M B) 1.82 × 10-8 M C) 1.35 × 10-4 M D) 3.31 × 10-16 M E) 9.1 × 10-9 M 7) 8) When titrating a monoprotic strong acid with a weak base at 25°C, the A) pH will be less than 7 at the equivalence point. B) titration will require more moles of the base than acid to reach the equivalence point. C) pH will be 7 at the equivalence point. D) pH will be greater than 7 at the equivalence point. E) titration will require more moles of acid than base to reach the equivalence point. 8) 9) A 100.0 mL sample of 0.10 M NH3 is titrated with 0.10 M HNO3. Determine the pH of the solution before the addition of any HNO3. The Kb of NH3 is 1.8 × 10-5. 9) A) 4.74 B) 12.55 C) 11.13 D) 13.00 E) 9.26 10) 10) Above what temperature does the following reaction become nonspontaneous? FeO(s) + CO(g) → CO2(g) + Fe(s) ΔH = -11.0 kJ; ΔS = -17.4 J/K A) 632 K B) 191 K C) 298 K D) This reaction is nonspontaneous at all temperatures. E) This reaction is spontaneous at all temperatures. 11) Calculate the pH of a solution formed by mixing 250.0 mL of 0.15 M NH 4Cl with 200.0 mL of 0.12 M NH3. The Kb for NH 3 is 1.8 × 10-5. A) 9.06 B) 4.55 C) 9.45 D) 9.26 12) Determine the equilibrium constant for the following reaction at 298 K. SO3(g) + H2O(g) → H2SO4(l) ΔG° = -90.5 kJ A) 0.964 B) 7.31 × 1015 C) 1.37 × 10-16 D) 9.11 × 10-8 E) 4.78 × 1011 E‐2 11) E) 4.74 12) Form V 13) 13) Which of the following solutions is a good buffer system? A) A solution that is 0.10 M HF and 0.10 M NaC 2H3O2 B) A solution that is 0.10 M HCl and 0.10 M NH4+ C) A solution that is 0.10 M HC2H3O2 and 0.10 M LiC2H3O2 D) A solution that is 0.10 M NaOH and 0.10 M KOH E) None of the above are buffer systems. 14) A solution containing AgNO3 is mixed with a solution of NaCl to form a solution that is 0.10 M in AgNO3 and 0.075 M in NaCl. What will happen once these solutions are mixed? Ksp (AgCl) = 1.77 × 10-10. A) Silver chloride will precipitate out of solution, leaving an unsaturated solution of AgCl. B) Silver chloride will precipitate out of solution, leaving a saturated AgCl solution. C) Nothing will happen since the molar solubility of AgCl is higher than the solution concentrations. D) Nothing will happen since NaCl and AgNO3 are both soluble compounds. E) There is not enough information to say anything about this solution. 14) 15) Determine the molar solubility of CaSO4 in a solution containing 0.100 M Na 2SO4. Ksp 15) (CaSO4) = 2.4 × 10-5. A) 2.4 × 10-4 M B) 5.8 × 10-10 M C) 4.9 × 10-3 M D) 1.2 × 10-5 M E) 0.10 M 16) Given the following equation, 16) N2O(g) + NO2(g) → 3 NO( g) ΔG° rxn = -23.0 kJ Calculate ΔG°rxn for the following reaction. 3N 2O(g) + 3NO 2(g) → 9 NO( g) A) 69.0 kJ B) 23.0 kJ C) -7.67 kJ D) -23.0 kJ E) -69.0 kJ 17) When titrating a weak monoprotic acid with NaOH at 25°C, the A) pH will be less than 7 at the equivalence point. B) pH will be equal to 7 at the equivalence point. C) titration will require more moles of base than acid to reach the equivalence point. D) titration will require more moles of acid than base to reach the equivalence point. E) pH will be greater than 7 at the equivalence point. E‐3 17) Form V 18) Use the free energies of formation given below to calculate the equilibrium constant (K) for the following reaction at 298 K. 2 HNO3(aq) + NO(g) → 3 NO 2(g) + H2O(l) -237.1 ΔG° f (kJ/mol) -110.9 87.6 51.3 18) Κ = ? A) 0.980 B) 1.02 C) 1.15 × 10-9 D) 5.11 × 10-4 E) 8.71 × 108 19) A 100.0 mL sample of 0.10 M NH3 is titrated with 0.10 M HNO3. Determine the pH of the solution after the addition of 100.0 mL of HNO3. The Kb of NH3 is 1.8 × 10-5. A) 3.44 B) 10.56 C) 6.58 D) 8.72 19) E) 5.28 20) Consider a reaction that has a positive ΔH and a positive ΔS. Which of the following statements is TRUE? A) This reaction will be spontaneous at all temperatures. B) This reaction will be nonspontaneous at all temperatures. C) This reaction will be nonspontaneous only at high temperatures. D) This reaction will be spontaneous only at high temperatures. E) It is not possible to determine without more information. 20) 21) Calculate the pH of a buffer that is 0.058 M HF and 0.058 M LiF. The K a for HF is 3.5 × 10-4. A) 3.46 B) 2.86 C) 9.31 D) 4.69 E) 10.54 21) 22) Which of the following processes shows a decrease in entropy of the system? A) 2 NO(g) + O 2(g) → 2 NO 2(g) B) CH3OH(l) → CO(g) + 2H2(g) C) COCl 2(g) → CO(g) + Cl 2(g) D) NaClO3(s) →Na+(aq) + ClO3-(aq) 22) E) None of the above will show a decrease in entropy. 23) You wish to prepare an HC 2H3O2 buffer with a pH of 4.24. If the pK a of is 4.74, what ratio of C2H3O2⁻/HC2H3O2 must you use? A) 0.50 B) 0.10 C) 2.8 D) 2.0 E) 0.32 23) 24) Which of the following is NOT true for ΔG rxn? A) If Q = 1, then ΔGrxn = ΔG°rxn. B) If ΔG° rxn = 0, the reaction is spontaneous in the reverse direction. C) Under equilibrium conditions, ΔGrxn = 0. D) If ΔG° rxn > 0, the reaction is spontaneous in the forward direction. E) If ΔG° rxn > 0, the reaction is spontaneous in the reverse direction. 24) E4 Form V 25) 25) Use Hessʹs law to calculate ΔG°rxn using the following information. ClO(g) + O3(g) → Cl(g) + 2 O 2(g) ΔG° rxn = ? 2 O3(g)→ 3 O2(g) Cl(g) + O3(g) → ClO(g) + O2(g) A) +262.1 kJ B) -210.3 kJ ΔG° rxn = +489.6 kJ ΔG° rxn = -34.5 kJ C) +455.1 kJ D) -472.4 kJ E) +524.1 kJ 26) A 100.0 mL sample of 0.10 M NH3 is titrated with 0.10 M HNO3. Determine the pH of the solution after the addition of 200.0 mL of HNO3. The Kb of NH3 is 1.8 × 10-5. A) 2.00 B) 12.52 C) 12.00 D) 6.44 26) E) 1.48 27) A 1.00 L buffer solution is 0.250 M in HF and 0.250 M in NaF. Calculate the pH of the solution after the addition of 100.0 mL of 1.00 M HCl. The Ka for HF is 3.5 × 10-4. A) 4.11 B) 2.78 C) 3.46 D) 3.09 E) 3.82 27) 28) Give the expression for the solubility product constant for PbCl2. [PbCl2] A) [Pb2+][Cl⁻]2 28) B) [Pb2+][Cl⁻]2 [PbCl2] C) [Pb2+][Cl⁻]2 D) [Pb2+]2[Cl⁻] [Pb2+]2[Cl⁻] E) [PbCl2] 29) Determine the molar solubility of BaF2 in a solution containing 0.0750 M LiF. Ksp (BaF2) = 1.7 × 10-6. A) 8.5 × 10-7 M B) 0.0750 M C) 1.2 × 10-2 M D) 3.0 × 10-4 M E) 2.3 × 10-5 M 29) 30) If the pKa of HCHO2 is 3.74 and the pH of an HCHO2/NaCHO2 solution is 3.11, which of the following is TRUE? A) [HCHO2] > [NaCHO2] B) [HCHO2] = [NaCHO2] C) [HCHO2] << [NaCHO2] D) [HCHO2] < [NaCHO2] E) It is not possible to make a buffer of this pH from HCHO2 and NaCHO 2. 30) 31) Which is the form number listed at the top of my exam? A) Form I B) Form II C) Form III 31) E‐5 D) Form IV E) Form V Answer Key Testname: EXAM3FALL2011 1) C 2) A 3) D 4) A 5) E 6) B 7) C 8) A 9) C 10) A 11) A 12) B 13) C 14) B 15) A 16) E 17) E 18) C 19) E 20) D 21) A 22) A 23) E 24) NY aNY ANSWER D 25) E 26) E 27) D 28) C 29) D 30) A 31) No Correct Answer Was Provided. E‐6 ...
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