CHEM 102 Winter 18 Make-up Exam (B) Questions and Answers,100% CORRECT

CHEM 102 Winter 18 Make-up Exam (B) Questions and Answers Potentially useful data: x  pH  pKa 2 a  log base acid  ΔG° = ΔH° – T ΔS° ΔG = ΔG° + RT ln Q ΔG° = – RT ln K R = 8.314 J mol-1 K-1 1. Please choose the letter “B” as your answer for this question. 2. Which of the following reactions has a negative S°? a) 2 H2 (g) + O2 (g)  2 H2O (g) b) BaF2 (s)  Ba2+ (aq) + 2 F (aq) c) CH3OH (aq)  CH3OH (l) d) All of the above. e) Both a) and c). 3. Rank the following substances in order of decreasing (that is, from highest to lowest) standard molar entropy. N2O4(g) NO(g) NO2(g) a) N2O4(g) > NO(g) > NO2(g) b) NO(g) > NO2(g) > N2O4(g) c) N2O4(g) > NO2(g) > NO(g) d) NO (g) > N2O4(g) > NO2(g) e) Since they are all gases, all have the same entropy. 4. Under which conditions is a chemical reaction non-spontaneous at all temperatures? a) S° > 0, H° > 0 b) S° < 0, H° > 0 c) S° < 0, H° < 0 d) S° > 0, H° < 0 e) Such a reaction does not exist. - 5. Which of the following MUST be true in a buffer solution in which [A ] > [HA]? a) pH > pKa b) pH = pKa c) pH < pKa d) pH < 7.00 e) pH > 7.00 6. Which equation could be used to calculate the molar solubility, S, of Fe(OH)2? a) Ksp = 2 S2 b) Ksp = S2 c) Ksp = S3 d) Ksp = 4 S3 e) Ksp = 2 S3 7. Calculate the pH of a solution made by mixing 250.0 mL of 0.150 M NH4Cl (Ka = 5.6 × 10-10) with 100.0 mL of 0.200 M NH3. a) 9.13 b) 8.98 c) 9.53 d) 4.74 e) 9.25 8. Use the data in the table below to determine S° for the following reaction: SO3 (g) + H2O (l)  H2SO4 (l) S° (J K-1 mol-1) SO3 (g) 256.2 H2O (l) 69.9 H2SO4 (l) 156.9 a) 169.2 J K-1 mol-1 b) 1343.2 J K-1 mol-1 c) – 169.2 J K-1 mol-1 d) – 29.4 J K-1 mol-1 e) 29.4 J K-1 mol-1 9. Which of the following aqueous mixtures CANNOT function as a buffer solution? a) H2CO3 and KHCO3 b) NH3 and (NH4)2SO4 c) HNO3 and NaNO3 d) CH3CH2COOH and CH3CH2COO-K+ e) NaH2PO4 and Na2HPO4 10. Consider 1 L of a buffer solution, in which [HF] = 0.10 M and [NaF] = 0.050 M. Which action will result in exceeding the buffer's capacity? a) adding 0.060 moles of HCl b) adding 0.20 moles of NaOH c) both a) and b) d) adding 0.01 moles of HCl e) adding 0.050 moles of NaOH 11. Choose the solution that will dissolve CuI(s) the least. a) 1 M MgI2(aq) b) 0.1 M MgI2(aq) c) 0.1 M CuSO4(aq) d) 0.05 M CuCl2(aq) e) 0.1 M NaI(aq) 12. The titration curve shown below most likely represents the titration of . a) a strong acid with a strong base b) a buffer with a strong base c) a polyprotic acid with a weak base d) a weak acid with a strong base e) a buffer with a weak base 13. If ΔG°f (C2H6) = –32.8 kJ/mol, ΔG°f (CO2) = –394.4 kJ/mol, and ΔG°f (H2O) = –237.1 kJ/mol, estimate the value of ΔG°rxn at 25 oC for the reaction given below. C2H6(g) + 7/2 O2 (g) → 2 CO2(g) + 3 H2O(l) a) - 598.7 kJ b) - 1467 kJ c) - 1442 kJ d) + 1615 kJ e) - 756 kJ 14. What is the pH of a solution made by mixing 40.0 mL of 0.100 M HCl with 25.0 mL of 0.100 M KOH? a) 0.64 b) 10.0 c) 12.3 d) 13.4 e) 1.64 15. Select the most suitable indicator for the titration of a strong acid with a strong base. a) bromothymol blue (transition range pH 6.0 to 7.6) b) methyl purple (transition range pH 4.8 to 5.4) c) thymolphthalein (transition range pH 9.3 to 10.5) d) methyl orange (transition range pH 3.1 to 4.4) e) None of the above. 16. Which of the following processes is non-spontaneous? a) the transfer of heat from a warm object to a cold one b) the decomposition of water into H2(g) and O2(g) gas c) the melting of ice at 25 oC d) the freezing of water at -5 oC e) the dissolution of table salt in water 17. Determine the molar solubility of CuCl (Ksp = 1.0 × 10-6) in a solution containing 0.04 M KCl. a) 1.0 × 10-12 M b) 4.0 × 10-8 M c) 2.5 × 10-5 M d) 1.0 × 10-3 M e) 5.0 × 10-12 M 18. A solution of NaF is added dropwise to a solution that is 0.0158 M in Ba2+. When the concentration of F- exceeds M, BaF2 (Ksp = 1.7 × 10-6) will precipitate. Neglect volume changes. a) 5.4 × 10–5 b) 2.6 × 10–3 c) 2.7 × 10–8 d) 1.0 × 10–2 e) 1.1 × 10–4 19. The solubility of Mn(OH)2 is 2.2 × 10–5 M. What is the Ksp of Mn(OH)2? a) 1.1 × 10–14 M b) 2.2 × 10–5 M c) 2.1 × 10–14 M d) 4.8 × 10–10 M e) 4.3 × 10–14 M 20. According to the Second Law of Thermodynamics, the . a) energy of the universe is constant b) entropy of the universe is increasing c) enthalpy of the universe is constant d) energy of the universe is decreasing e) entropy of the universe is constant 21. What is the correct expression for the solubility product constant of magnesium fluoride, MgF2? a) 2[F-] [Mg2+] b) [Mg2+][F-]2 c) [Mg2+][F-]2 / [MgF2] d) [MgF2] / [Mg2+][F-]2 e) 1 / [Mg2+][F-]2 22. You are asked to prepare a buffer solution of pH 3.68 by using lactic acid (Ka = 1.8 x 10-4) and sodium lactate. What mole ratio of conjugate base to acid should you use? a) 1.15 to 1 b) 1 to 1 c) 0.87 to 1 d) 3.68 to 1 e) either a) or c) 23. What happens to the solubility equilibrium of 0.1 M Ca(OH)2 if HCl is added? The equilibrium will . a) shift to the right because both the [Ca2+] and [OH-] decrease b) shift to the left because the [OH-] increases c) not shift, since HCl does not appear in the Ksp expression d) shift to the right because the [OH-] decreases e) shift to the left because the [Cl-] increases 24. What would be best to use to make a buffer solution with a neutral pH? a) an equimolar mixture of a strong acid and a strong base b) an equimolar mixture of an extremely weak acid and an extremely strong base c) a weak acid with a pKa near -7 and its conjugate base d) a weak acid with a Ka near 1.00  10-7 and its conjugate base e) None of the above. 25. Which of the following statements is TRUE? a) Indicators show when an end point is reached in a titration. b) A titration curve is a plot of pH vs. the [base]/[acid] ratio. c) A titration of a weak acid with a strong base has an equivalence point at a pH below 7. d) A pH indicator will always change color at the equivalence point in a titration. e) All of the above statements are false. 26. Consider the decomposition reaction below: CCl4 (g) C (s) + 2 Cl2 (g) If ΔH = 95.7 kJ and ΔS = 142.2 J/K, which of the following statements is TRUE? a) The process is spontaneous below 673 K. b) The process is spontaneous above 673 K. c) The process is spontaneous only at 673 K. d) The process is spontaneous at any temperature. e) The process is non-spontaneous at any temperature. chem102w18_make-up exam B Answer Section MULTIPLE CHOICE 1. ANS: B PTS: 0 2. ANS: E PTS: 1 3. ANS: C PTS: 1 4. ANS: B PTS: 1 5. ANS: A PTS: 1 6. ANS: D PTS: 1 7. ANS: B PTS: 1 8. ANS: C PTS: 1 9. ANS: C PTS: 1 10. ANS: C PTS: 1 11. ANS: A PTS: 1 12. ANS: D PTS: 1 13. ANS: B PTS: 1 14. ANS: E PTS: 1 15. ANS: A PTS: 1 16. ANS: B PTS: 1 17. ANS: C PTS: 1 18. ANS: D PTS: 1 19. ANS: E PTS: 1 20. ANS: B PTS: 1 21. ANS: B PTS: 1 22. ANS: C PTS: 1 23. ANS: D PTS: 1 24. ANS: D PTS: 1 25. ANS: A PTS: 1 26. ANS: B PTS: 1