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REVIEW Q’s

REVIEW Q’s. A titration of an acid and base to the equivalence point results in a noticeably acidic solution. It is likely this titration involves A . a strong acid and a weak base. B . a weak acid and a strong base. C . a weak acid and a weak base (where K a equals K b ).

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REVIEW Q’s

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  1. REVIEW Q’s

  2. A titration of an acid and base to the equivalence point results in a noticeably acidic solution. It is likely this titration involves A. a strong acid and a weak base. B. a weak acid and a strong base. C. a weak acid and a weak base (where Ka equals Kb). D. a strong acid and a strong base.

  3. For PbCl2 (Ksp = 2.4  10–4), will a precipitate of PbCl2 form when 0.10 L of 3.0  102 M Pb(NO3)2 is added to 400 mL of 9.0  102 M NaCl? A. Yes, because Q > Ksp. B. No, because Q < Ksp. C. No, because Q = Ksp. D. Yes, because Q < Ksp.

  4. The molar solubility of magnesium carbonate is 1.8  104mol/L. What is Ksp for this compound? A. 1.8  104 B. 3.6  104 C. 1.3  107 D. 3.2  108 E. 2.8  1014

  5. The solubility product for chromium(III) fluoride is Ksp = 6.6  1011. What is the molar solubility of chromium(III) fluoride? A. 1.6  103 M B. 1.2  103 M C. 6.6  1011 M D. 2.2  103 M E. 1.6  106 M

  6. Calculate the concentration of chloride ions in a saturated lead(II) chloride (Ksp = 2.4  104) solution. A. 2.4  104 M B. 4.8  104 M C. 3.9  102 M D. 1.2  101 M E. 7.8  102 M

  7. Calculate the minimum concentration of Cr3+ that must be added to 0.095 M NaF in order to initiate a precipitate of chromium(III) fluoride. (For CrF3 , Ksp = 6.6  1011.) A. 0.023 M B. 0.032 M C. 7.7  108 M D. 2.9  109 M E. 6.9  1010 M

  8. Will a precipitate (ppt) form when 300. mL of 5.0  105 M AgNO3 are added to 200. mL of 2.5  107 M NaBr? Answer yes or no, and identify the precipitate if there is one. A. Yes, the ppt is AgNO3(s). B. Yes, the ppt is AgBr(s). C. Yes, the ppt is NaBr(s). D. Yes, the ppt is NaNO3(s). E. No, a precipitate will not form.

  9. Arrange the following substances in the order of increasing entropy at 25C. HF(g), NaF(s), SiF4(g), SiH4(g), Al(s) lowest  highest A. SiF4(g) < SiH4(g) < NaF(s) < HF(g) < Al(s) B. HF(g) < Al(s) < NaF(s) < SiF4(g) < SiH4(g) C. Al(s) < NaF(s) < HF(g) < SiH4(g) < SiF4(g) D. Al(s) < HF(g) < NaF(s) < SiF4(g) < SiH4(g) E. NaF(s) < Al(s) < HF(g) < SiF4(g) < SiH4(g)

  10. Which response includes all the following processes that are accompanied by an increase in entropy? 1. 2SO2(g) + O2(g)  SO3(g) 2. H2O(l)  H2O(s) 3. Br2(l)  Br2(g) 4. H2O2(l)  H2O(l) + (1/2)O2(g) A. 1, 2, 3, 4 B. 1, 2 C. 2, 3, 4 D. 3, 4 E. 1, 4

  11. Which response includes all the following processes that are accompanied by an increase in entropy? 1. I2(s)  I2(g) 2. 2I(g)  I2(g) 3. 2NH3(g)  N2(g) + 3H2(g) 4. Mg2+(aq) + 2OH(aq)  Mg(OH)2(s) A. 1, 2 B. 1, 3 C. 3, 4 D. 3 E. 2, 4

  12. Determine S for the reaction SO3(g) + H2O(l)  H2SO4(l). S(J/K·mol) SO3 256.2 H2O 69.9 H2SO4 156.9 A. 169.2 J/K·mol B. 1343.2 J/K·mol C. 169.2 J/K·mol D. 29.4 J/K·mol E. 29.4 J/K·mol

  13. A negative sign for G indicates that, at constant T and P, A. the reaction is exothermic. B. the reaction is endothermic. C. the reaction is fast. D. the reaction is spontaneous. E. S must be > 0.

  14. Calculate G for the reaction 3NO2(g) + H2O(l)  2HNO3(l) + NO(g). Gf (kJ/mol) H2O(l) 237.2 HNO3(l) 79.9 NO(g) 86.7 NO2(g) 51.8 A. 8.7 kJ/mol B. 192 kJ/mol C. 414 kJ/mol D. 192 kJ/mol E. 155 kJ/mol

  15. Ozone (O3) in the atmosphere can reaction with nitric oxide (NO): O3(g) + NO(g)  NO2(g) + O2(g). Calculate the G for this reaction at 25C. (H = 199 kJ/mol, S = 4.1 J/K·mol) A. 1020 kJ/molB. 1.22  103 kJ/mol C. 2.00  103 kJ/mol D. 1.42  103 kJ/mol E. 198 kJ/mol

  16. For the reaction H2(g) + S(s)  H2S(g), H = 20.2 kJ/mol and S = +43.1 J/K·mol. Which of the following statements is true? A. The reaction is only spontaneous at low temperatures. B. The reaction is spontaneous at all temperatures. C. G becomes less favorable as temperature increases. D. The reaction is spontaneous only at high temperatures. E. The reaction is at equilibrium at 25C under standard conditions.

  17. At 1500C the equilibrium constant for the reaction CO(g) + 2H2(g) CH3OH(g) has the value Kp = 1.4  107. Calculate G for this reaction at 1500C. A. 105 kJ/mol B. 1.07 kJ/mol C. 233 kJ/mol D. 105 kJ/mol E. 233 kJ/mol

  18. The element oxygen was prepared by Joseph Priestley in 1774 by heating mercury(II) oxide: HgO(s)  Hg(l) + (1/2)O2(g), H = 90.84 kJ/mol. Estimate the temperature at which this reaction will become spontaneous under standard state conditions. S(Hg) = 76.02 J/K·mol S(O2) = 205.0 J/K·mol S(HgO) = 70.29 J/K·mol A. 108 K B. 430 K C. 620 K D. 775 K E. 840 K

  19. Calculate the equilibrium constant for the decomposition of water, 2H2O(l) 2H2(g) + O2(g) at 25C, given that Gf(H2O(l)) = –237.2 kJ/mol. A. 0.83 B. 6.3  1084 C. 2.5  1042 D. 1.6  1083 E. 4.7  105

  20. Complete and balance the following redox equation. When properly balanced using the smallest whole-number coefficients, the coefficient of S is H2S + HNO3 S + NO (acidic solution) A. 1 B. 2 C. 3 D. 5 E. 6

  21. Complete and balance the following redox equation. What is the coefficient of H2O when the equation is balanced with the set of smallest whole-number coefficients? H2O + MnO4 + I MnO2 + IO3 (basic solution) A. 1 B. 2 C. 4 D. 10 E. None of these.

  22. Given the following notation for an electrochemical cell Pt(s) | H2(g) | H+(aq) || Ag+(aq) | Ag(s), what is the balanced overall (net) cell reaction? A. 2H+(aq) + 2Ag+(aq)  H2(g) + 2Ag(s) B. H2(g) + 2Ag(s)  H+(aq) + 2Ag+(aq) C. 2H+(aq) + 2Ag(s)  H2(g) + 2Ag+(aq) D. H2(g) + Ag+(aq)  H+(aq) + Ag(s) E. H2(g) + 2Ag+(aq)  2H+(aq) + 2Ag(s)

  23. Consider an electrochemical cell constructed from the following half cells, linked by a KCl salt bridge. • a Fe electrode in 1.0 M FeCl2 solution • a Sn electrode in 1.0 M Sn(NO3 )2solution When the cell is running spontaneously, which choice includes only true statements and no false ones? A. The tin electrode loses mass and the tin electrode is the cathode. B. The tin electrode gains mass and the tin electrode is the cathode. C. The iron electrode gains mass and the iron electrode is the anode. D. The iron electrode loses mass and the iron electrode is the cathode. E. The iron electrode gains mass and the iron electrode is the cathode.

  24. A certain electrochemical cell has for its cell reaction: Zn + HgOZnO + Hg Which is the half-reaction occurring at the anode? A. HgO + 2e Hg + O2 B. Zn2+ + 2e Zn C. Zn  Zn2+ + 2e D. ZnO + 2e Zn

  25. Calculate the value of Ecell for the following reaction: 2Au(s) + 3Ca2+(aq)  2Au3+(aq) + 3Ca(s) A. 4.37 V B. 1.37 V C. 11.6 V D. 1.37 V E. 4.37 V

  26. Calculate Ecell for a silver-aluminum cell in which the cell reaction is Al(s) + 3Ag+(aq)  Al3+(aq) + 3Ag(s) A. 2.46 V B. 0.86 V C. 0.86 V D. 2.46 V E. none of these

  27. Consider an electrochemical cell based on the following cell diagram: Pt | Pu3+(aq), Pu4+(aq) || Cl2(g), Cl(aq) | Pt Given that the standard cell emf is 0.35 V and that the standard reduction potential of chlorine is 1.36 V, what is the standard reduction potential E(Pu4+/Pu3+)? A. 2.37 V B. 1.01 V C. 1.71 V D. 1.01 V E. 1.71 V

  28. An electrochemical cell based on the following reaction has a standard cell voltage (Ecell) of 0.48 V: Sn(s) + Cu2+(aq)  Sn2+(aq) + Cu(s) What is the standard reduction potential of tin(II)? (E(Cu2+/Cu) = 0.34 V) A. 0.14 V B. 0.14 V C. 0.82 V D. 0.82 V E. none of these

  29. According to the following cell diagram, which chemical species undergoes reduction? Sn| Sn2+ || NO3(acid soln), NO(g) | Pt A. Sn B. Sn2+ C. NO3 D. NO E. Pt

  30. In the following half equation, which is the oxidizing agent? NO3(aq) + 4H+(aq) + 3e NO(g) + 2H2O A. NO3 B. H+ C. e D. NO E. H2O

  31. Which statement is true for a spontaneous redox reaction carried out at standard-state conditions? A. Ered is always negative. B. Ecell is always positive. C. Eox is always positive. D. Ered is always positive.

  32. Which one of the following reactions will occur spontaneously at standard-state conditions and 25C? A. Mg2+ + Ca Mg + Ca2+ B. Au + 3K+ Au3+ + 3K C. 2Al3+ + 3Fe  2Al + 3Fe2+ D. Cu + 2H+ Cu2+ + H2

  33. Consider the following standard reduction potentials in acid solution: E(V) Al3+ + 3e Al(s) 1.66 AgBr(s) + e Ag(s) + Br +0.07 Sn4+ + 2e Sn2+ +0.14 Fe3+ + e Fe2+ +0.77 The strongest oxidizing agent among those shown above is A. Fe3+. B. Fe2+. C. Br. D. Al3+. E. Al.

  34. Using a table of standard electrode potentials, decide which of the following statements is completely true. A. Cu2+ can oxidize H2, and Fe can reduce Mn2+. B. Ni2+ can oxidize Cu2+, and Fe2+ can reduce H+. C. Fe2+ can oxidize H2, and Fe2+ can reduce Au3+. D. Br2 can oxidize Ni, and H2 can reduce Mn2+. E. H+ can oxidize Fe, and Ni can reduce Br2.

  35. Determine the equilibrium constant, Keq, at 25C for the reaction 2Br(aq) + I2(s) Br2(l) + 2I(aq) A. 5.7  1019 B. 18.30 C. 1.7  1054 D. 1.9  1018 E. 5.7  1055

  36. Consider the reaction Fe + Sn2+(1.0 M)  Fe2+(1.0 M) + Sn. a. Calculate the voltage theoretically generated by the cell. b. Sketch a diagram of such a cell. Be sure to label the anode and cathode, and show the direction of electron flow in the external circuit. Write the half-reactions occurring at the electrodes. c. Show the direction in which the Cl ions in the KCl salt bridge will flow.

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