exam3fall2011f1

exam3fall2011f1 - Third Examination Fall 2011 Form I...

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Unformatted text preview: Third Examination Fall 2011 Form I 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) Which of the following solutions is a good buffer system? A) A solution that is 0.10 M HC2H3O2 and 0.10 M LiC2H3O2 B) A solution that is 0.10 M HCl and 0.10 M NH4+ 1) C) A solution that is 0.10 M NaOH and 0.10 M KOH D) A solution that is 0.10 M HF and 0.10 M NaC 2H3O2 E) None of the above are buffer systems. 2) 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. 2) 3) 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) 0.10 B) 2.8 C) 0.32 D) 0.50 E) 2.0 3) 4) 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) 9.31 B) 10.54 C) 2.86 D) 4.69 E) 3.46 4) 5) 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. 5) A) 9.26 B) 9.45 C) 4.55 D) 9.06 E) 4.74 6) 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 6) B) HC7H5O2, Ka = 6.5 x 10-5 C) HClO, Ka = 2.9 x 10-8 D) HF, Ka = 3.5 x 10-4 E) HCN, Ka = 4.9 x 10-10 7) When titrating a monoprotic strong acid with a weak base at 25°C, the A) pH will be greater than 7 at the equivalence point. B) titration will require more moles of the base than acid to reach the equivalence point. C) titration will require more moles of acid than base to reach the equivalence point. D) pH will be less than 7 at the equivalence point. E) pH will be 7 at the equivalence point. A‐1 7) Form I 8) When titrating a weak monoprotic acid with NaOH at 25°C, the A) pH will be less than 7 at the equivalence point. B) titration will require more moles of acid than base to reach the equivalence point. C) pH will be equal to 7 at the equivalence point. D) titration will require more moles of base than acid to reach the equivalence point. E) pH will be greater than 7 at the equivalence point. 8) 9) 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) 3.46 B) 3.09 C) 3.82 D) 4.11 E) 2.78 9) 10) 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) 12.36 B) 13.36 C) 10.00 D) 1.64 E) 0.64 10) 11) 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. 11) A) 9.26 B) 12.55 C) 13.00 D) 4.74 E) 11.13 12) 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) 12.52 B) 2.00 C) 1.48 D) 6.44 E) 12.00 13) 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) 6.58 C) 10.56 D) 8.72 12) 13) E) 5.28 14) Determine the molar solubility of CaSO4 in a solution containing 0.100 M Na 2SO4. Ksp 14) (CaSO4) = 2.4 × 10-5. A) 5.8 × 10-10 M B) 4.9 × 10-3 M C) 2.4 × 10-4 M D) 0.10 M E) 1.2 × 10-5 M 15) Give the expression for the solubility product constant for PbCl2. [PbCl2] A) [Pb2+][Cl⁻]2 B) [Pb2+][Cl⁻]2 [PbCl2] C) [Pb2+]2[Cl⁻] [PbCl2] D) [Pb2+][Cl⁻]2 E) [Pb2+]2[Cl⁻] A‐2 15) Form I 16) Determine the molar solubility of BaF2 in a solution containing 0.0750 M LiF. Ksp (BaF2) = 1.7 × 10-6. A) 1.2 × 10-2 M B) 0.0750 M C) 8.5 × 10-7 M D) 2.3 × 10-5 M E) 3.0 × 10-4 M 16) 17) Determine the molar solubility of PbSO4 in pure water. Ksp (PbSO4) = 1.82 × 10-8. A) 1.35 × 10-4 M B) 3.31 × 10-16 M C) 1.82 × 10-8 M D) 4.48 × 10-4 M E) 9.1 × 10-9 M 17) 18) A ligand is a molecule or ion that acts as a A) Bronsted-Lowry acid B) Lewis base C) Bronsted-Lowry base D) Lewis acid E) none of the above 18) 19) 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) Nothing will happen since NaCl and AgNO3 are both soluble compounds. B) Nothing will happen since the molar solubility of AgCl is higher than the solution concentrations. C) Silver chloride will precipitate out of solution, leaving an unsaturated solution of AgCl. D) Silver chloride will precipitate out of solution, leaving a saturated AgCl solution. E) There is not enough information to say anything about this solution. 19) 20) Which of the following processes shows a decrease in entropy of the system? A) COCl 2(g) → CO(g) + Cl 2(g) B) CH3OH(l) → CO(g) + 2H2(g) C) 2 NO(g) + O 2(g) → 2 NO 2(g) D) NaClO3(s) →Na+(aq) + ClO3-(aq) 20) E) None of the above will show a decrease in entropy. 21) Which of the following relationships is correct at constant T and P? A) ΔG < 0 represents a nonspontaneous process B) ΔG > 0 represents a spontaneous process C) ΔG > 0 represents an increase in kinetic energy D) ΔG is proportional to -ΔSuniv E) All of the above are correct A‐3 21) Form I 22) 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 only at high temperatures. C) This reaction will be spontaneous only at high temperatures. D) This reaction will be nonspontaneous at all temperatures. E) It is not possible to determine without more information. 22) 23) Above what temperature does the following reaction become nonspontaneous? 23) FeO(s) + CO(g) → CO2(g) + Fe(s) ΔH = -11.0 kJ; ΔS = -17.4 J/K A) 191 K B) 298 K C) 632 K D) This reaction is nonspontaneous at all temperatures. E) This reaction is spontaneous at all temperatures. 24) Calculate ΔS°rxn for the following reaction. The S° for each species is shown below the reaction. S°(J/mol·K) A) -112.3 J/K 24) C2H2(g) + H2(g) → C2H4(g) 200.9 130.7 219.3 B) -550.9 J/K C) +550.9 J/K D) +112.3 J/K E) +337.1 J/K 25) Given the following equation, 25) 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) -7.67 kJ B) 23.0 kJ C) -23.0 kJ D) 69.0 kJ E) -69.0 kJ 26) Estimate ΔG°rxn for the following reaction at 775 K. 2 Hg(g) + O 2(g) → 2 HgO(s) A) -625 kJ B) +321 kJ 26) ΔH°= -304.2 kJ; ΔS°= -414.2 J/K C) +17 kJ A‐4 D) -110 kJ E) -181 kJ Form I 27) 27) 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) -210.3 kJ B) +455.1 kJ ΔG° rxn = +489.6 kJ ΔG° rxn = -34.5 kJ C) +524.1 kJ D) +262.1 kJ E) -472.4 kJ 28) Determine the equilibrium constant for the following reaction at 298 K. SO3(g) + H2O(g) → H2SO4(l) 28) ΔG° = -90.5 kJ A) 4.78 × 1011 B) 0.964 C) 1.37 × 10-16 D) 9.11 × 10-8 E) 7.31 × 1015 29) 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 29) Κ = ? A) 0.980 B) 1.15 × 10-9 C) 5.11 × 10-4 D) 1.02 E) 8.71 × 108 30) Which of the following is NOT true for ΔG rxn? A) If ΔG° rxn = 0, the reaction is spontaneous in the reverse direction. B) If ΔG° rxn > 0, the reaction is spontaneous in the reverse direction. C) If Q = 1, then ΔGrxn = ΔG°rxn. D) If ΔG° rxn > 0, the reaction is spontaneous in the forward direction. E) Under equilibrium conditions, ΔGrxn = 0. 31) Which is the form number listed at the top of my exam? A) Form I B) Form II C) Form III A‐5 30) 31) D) Form IV E) Form V Answer Key Testname: EXAM3FALL2011 1) A 2) D 3) C 4) E 5) D 6) A 7) D 8) E 9) B 10) D 11) E 12) C 13) E 14) C 15) D 16) E 17) A 18) B 19) D 20) C 21) D 22) C 23) C 24) A 25) E 26) C 27) C 28) E 29) B 30) --D Any 31) No Correct Answer Was Provided. A‐6 ...
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