Chem 1043 Final Review PDF

CHEM 1043 Final Review 1. The energy transferred as the result of a temperature difference is defined as________. A) Kinetic energy B) Potential energy C) Heat D) Enthalpy E) Entropy ANS C 2. During a spontaneous chemical reaction, it is found that Ssys is less than 0....

CHEM 1043 Final Review 1. The energy transferred as the result of a temperature difference is defined as________. A) Kinetic energy B) Potential energy C) Heat D) Enthalpy E) Entropy ANS C 2. During a spontaneous chemical reaction, it is found that Ssys is less than 0. This means _____ A)  Ssurr is less than 0 and its magnitude is less than  Ssys. B)  Ssurr is less than 0 and its magnitude is greater than  Ssys. C)  Ssurr is greater than 0 and its magnitude is less than  Ssys. D)  Ssurr is greater than 0 and its magnitude is greater than  Ssys. E) an error has been made, as Ssys is greater than 0 by necessity for a spontaneous process ANS D 3. When solid pellets of sodium hydroxide (NaOH) dissolve in water, the temperature of the water can rise dramatically. Considering NaOH as the system, what can you deduce about the sign of the entropy change of the system (Ssys) and the surrounding (Ssurr) for this case? A) Ssys is less than 0 and  Ssurr is less than 0. B)  Ssys is less than 0 and  Ssurr is greater than 0. C)  Ssys is greater than 0 and  Ssurr is less than 0. D)  Ssys is greater than 0 and  Ssurr is greater than 0. E) Nothing can be deduced from this limited information. ANS D 4. Which one of the following statements regarding reaction rates and kinetic molecular theory is not true? A) Higher concentrations of reactants typically lead to greater reaction rates because a larger number of effective molecular collisions occur. B) Collisions between product molecules that reform reactant molecules do not affect the overall rate of reaction. C) The actual dependence of reaction rate on concentration must be determined experimentally because it depends on the reaction mechanism. D) At t = 0, the maximum rate should be observed because only reactant molecules are present. E) As the reaction proceeds, fewer reactant molecules are present and the reaction rate typically decreases. ANS: B 5. A reaction mechanism consists of a series of __________ steps. A) molecular B) elementary C) primary D) secondary E) steric ANS: B 6. A proposed mechanism for the decomposition of ozone in the stratosphere is: Step 1: Cl(g) + O3(g) → ClO(g) + O2(g) Step 2: ClO(g) + O3(g) → Cl(g) + 2 O2(g) Which of the following species is an intermediate? A) Cl B) O2 C) O3 D) This mechanism has no intermediates. E) ClO ANS: E 7. A proposed mechanism for the reduction of nitrogen as NO by hydrogen is: Step 1: H2(g) + 2 NO(g) N2O(g) + H2O(g) (slow) Step 2: N2O(g) + H2(g) N2(g) + H2O(g) (fast) Which of the following statements is NOT true? A) The energy profile for this reaction probably has two maxima. B) The reaction rate is probably second order in NO. C) The reaction rate is probably first order in H2. D) N2O is an intermediate. E) The activation energy for step 2 is probably less than that of step 1 ANS: D 8. A chemical equilibrium 2 A ⇄ B has a forward rate constant, kf = 5 M–1 s–1, and a reverse rate constant, kr = 10 s–1. If the system has a concentration of [A] = 0.10 M at equilibrium, what is the concentration of B at equilibrium? A) 0.5 B) 2 C) 0.05 D) 0.005 E) 0.2 ANS: D 9. Which of the following statements regarding the equilibrium constant is NOT true? A) When K >> 1, the concentration of products is much greater than the concentrations of reactants at equilibrium. B) When K > 1, the products and reactants come to equilibrium rapidly. ANS: E 10. The initial rate data for the reaction 2 N2O5(g) → 4NO2(g) + O2(g) is shown in the following table. Determine the value of the rate constant for this reaction. Experiment [N2O5](M) Rate (M/s) 1 2.56 x103 450 2 2 1.28 x10 22.5 –1 –1 a. 4.09 s b. 0.176 s c. 0.0569 s–1 d. 0.225 s–1 e. 80.1 s–1 ANS: B 11. For the equilibrium, 2 PH3(g) P2(g) + 3 H2(g), the equilibrium partial pressures are PPH3 = 0.022 atm, PP2 = 0.289 atm, and PH2 = 0.867 atm at 873 K. Calculate Kp. A) 0.0585 B) 2.50 x 10–3 C) 17.1 D) 389 E) 0.0441 ANS: B 12. If the reaction quotient Q has a larger value than the related equilibrium constant, K, _______ a. the reaction is at equilibrium. b. the reaction will continue to make more products. c. the reaction will consume products and make reactants. d. the reaction will release heat to achieve equilibrium. e. the value of K will increase until it is equal to Q. ANS: C 13. Which one of the following is NOT a conjugate acid–base pair? a. NH3 and NH4+ b. H3O+ and OH– c. H2PO4– and HPO42– d. HS– and H2S e. NH3 and NH2– ANS: B 14. Solutions of sodium salts of the acids in the following table are prepared with an initial concentration of 0.500 M. Which solution will have the highest pH and be the most basic? Acid pKa HA 4.00 HB 7.00 HC 10.00 HD 11.00 A) NaA B) NaB C) NaC D) NaD E) All will have the same pH because the concentrations are the same. ANS: D 15. A cup of coffee has a hydroxide ion concentration of 1 x 10–10 M. What is the pH of this coffee? A) 1.0 x 10–4 B) 7.0 C) 4.0 D) –10.0 E) 10.0 ANS: C 16. What is the hydronium ion concentration of a 0.010 M acetic acid solution? (Ka for acetic acid is 1.76 x 10–5.) A) 1.8 x 10–3 B) 1.8 x 10–7 C) 1.8 x 10–5 D) 4.2 x 10–4 E) 1.0 x 10–2 ANS: D 17. What is the concentration of [OH–] in a 0.20 M ammonia solution? (The Kb value for ammonia is 1.8 x 10–5.) A) 3.6 x 10–6 M B) 1.9 x 10–3 M C) 1.8 x 10–5 M D) 4.2 x 10–4 M E) 0.20 M ANS: B 18. When values of Ka are small (e.g., 1 x 10–5) and concentrations of weak acids [HA] are relatively large (e.g., 0.10 M), the hydronium ion concentration of the solution can be calculated using which expression? A) [H+] = Ka B) [H+] = Ka[HA] C) [H +] = (Ka [HA])1/2 D) [H+] = KaKb[HA] E) [H+] = Ka[HA]/[A–] ANS: C 19. Which one of the following salts forms aqueous solutions with pH = 7? A) Na2S B) NaNO2 C) NaBr D) Na2CO3 E) NaClO2 ANS: C 20. A buffer solution is made such that the initial concentrations of lactic acid (HC3H5O3) and the lactate ion (C3H5O3–) are 0.600 M and 0.620 M, respectively. What is the resulting pH if 100.0 mL of 0.100 M potassium hydroxide is added to 0.500 L of the buffer solution? (The Ka of HC3H5O3 is 1.4 x 10–4.) A) 3.81 B) 4.96 C) 3.90 D) 3.85 E) 2.75 ANS: C 21. To simulate the pH of blood, which is 7.4, a buffer solution made by dissolving sodium dihydrogen phosphate (Ka = 6.2 x 10–8) and sodium hydrogen phosphate (Ka = 3.6 x 10–13) together in an aqueous solution can be used. What mole ratio of Na2HPO4/NaH2PO4 is required to produce a solution with a pH of 7.4? A)1.2 B)1.0 C)1.6 D)0.96 E)0.90 ANS: C 22. Halfway to the equivalence point in a titration curve of a weak acid with a strong base, __________ A) nothing is happening yet. B) pH = pKa of the indicator. C) pH = pKa of the weak acid. D) the pH has not yet changed. E) pH = 3.5 exactly. ANS: B 23. A 200.0 mL solution of 0.40 M ammonium chloride was titrated with 0.80M sodium hydroxide. What was the pH of the solution after 50.0 mL of the NaOH solution were added? The Kb of ammonia is 1.76 x 10–5. A) 9.25 B) 5.02 C) 4.75 D) 8.98 E) 11.22 ANS: A 24. Reduction is the ________ A. gain of electrons. B. loss of electrons. C. gain of protons. D. loss of protons. E. loss of mass. ANS: A 25. What is the oxidation number of chromium in the ionic compound ammonium dichromate, (NH4)2Cr2O7? A. +3 B. +4 C. +5 D. +6 E. +7 ANS: D 26. A voltaic cell is constructed based on the reaction of Zn(s) with Pb2+(aq) producing Zn2+(aq) and Pb(s). Identify the correct cell diagram. A) Zn2+(aq) | Pb2+(aq) || Zn(s) | Pb(s) B) Pb2+(aq) | Pb(s) || Zn(s) | Zn2+(aq) 2+ 2+ C) Zn(s) | Zn (aq) || Pb (aq) | Pb(s) D) Pb(s) | Pb2+(aq) || Zn2+(aq) | Zn(s) 2+ 2+ E) Zn(s) | Pb (aq) || Zn (aq) | Pb(s) ANS: C 27. A voltaic cell is constructed based on the reaction of Ag(CN)2-(aq) with Cr(s) producing Ag(s) and Cr3+(s). Identify the correct cell diagram. A) Ag(CN)2-(aq) | Cr(s) || Ag(s) | Cr3+(aq) B) Ag(CN)2-(aq) | Ag(s) || Cr(s) | Cr3+(aq) C) Ag(s) | Cr3+(aq) || Ag(CN)2-(aq) | Cr(s) D) Cr(s) | Cr3+(aq) || Ag(CN)2-(aq) | Ag(s) E) Cr(s) | Cr3+(aq) || Ag(s) | Ag(CN)2-(aq) ANS: D 28. Use the table of standard reduction potentials below to identify which of the following statements is NOT correct. Half-reaction E° Pb + 2 e Pb 4+ - 2+ +1.80 Au3+ + 3 e- Au +1.50 Br2 + 2 e-2 Br - +1.066 Fe + 3 e Fe 3+ - +0.771 I2 + 2 e 2 I - - +0.535 Pb + 2 e Pb 2+ - -0.124 Al + 3 e Al 3+ - -1.66 Mg + 2 e Mg 2+ - -2.37 K +e K + - -2.93 4+ A) Pb will oxidize all of the species on the right side of the arrows in the other half-reactions. B) K+ will reduce all of the species on the left side of the arrows in the other half-reactions. C) I2 is a better reducing agent than Pb2+. D) Al is easier to oxidize than Fe. E) Mg is a better reducing agent than Pb ANS: C 29. Based on the information in the table of standard reduction potentials below, calculate for Al(s) | Al3+(aq) || Br2(aq), Br -(aq). Half-reaction E° Pb + 2 e Pb 4+ - 2+ +1.80 Au + 3 e Au 3+ - +1.50 Br2 + 2 e 2 Br - - +1.066 Fe + 3 e Fe 3+ - +0.771 I2 + 2 e 2 I - - +0.535 Pb + 2 e Pb 2+ - -0.124 Al + 3 e Al 3+ - -1.66 Mg + 2 e Mg 2+ - -2.37 K +e K + - -2.93 A) +0.12 V B) -0.59 V C) +2.73 V D) +0.59 V E) -2.73 V ANS: C 30. An electrochemical cell is constructed with a zinc metal anode in contact with a 0.052 M solution of zinc nitrate and a silver cathode in contact with a 0.0042 M solution of silver(I) nitrate. What is the value of Q to use in the Nernst equation for this cell? A) 2.9 x 103 B) 3.4 x 10–4 C) 12 D)1.00 E) 8.1 x 10–2 ANS: A 31. What is the cell potential of an electrochemical cell at 298 K with a copper metal electrode immersed in a 0.30 M copper sulfate solution in one compartment and a copper metal electrode immersed in a 1.5 M copper sulfate solution in the other compartment? Cu2+(aq) + 2 e-® Cu(s), = +0.34 V A) +0.34 V B)+0.68 V C) -0.34 V D) +0.021 V E) More information is needed to decide. ANS: D 32. The unit of current, the ampere (A), is defined as ________ A) 1 C. B) 1 mole of electrons per second. C) 1 C/s. D) 96,500 C/s. E) 1 mole of electrons. ANS: C 33. Hydrogen reacts with nitrogen to form ammonia (NH3) according to the reaction  3 H2(g) + N2(g)  2 NH3(g) H° is –92.38 kJ/mol, and DS° is –198.2 J/mol · K. Determine G° at 298 K. A) 5.897 x104 kJ/mol B) 297.8 kJ/mol C) –33.32 kJ/mol D) –16.66 kJ/mol 4 E) -5.9 x 10 kJ/mol ANS = C 34. Determine the overall order of the reaction 2 NO(g) + Cl2(g) 2 NOCl(g) from the following data: Experiment [NO] (M) [Cl2] (M) Rate (M/s) 1 0.0300 0.0100 3.4 x 10-4 2 0.0150 0.0100 8.5 x 10-5 3 0.0150 0.0400 3.4 x 10-4 a. 1 b. 2 c. 3 d. 4 e) 5 ANS= C 35. Which of the following reaction pathways shows the effect of a catalyst (black) on an uncatalyzed reaction (gray)? ANS = B 36. A reaction is first order in A. If the rate constant of the reaction is 3.45 x 10–3 s–1, what is the half-life (t1/2) of the reaction? A) 4.98. 10–3 s B) 200 s C) 3.45. 10–3 s D) 100 s ANS = B 37. In the following reaction in aqueous solution, the acid reactant is __________, and its conjugate base product is __________. CH3NH2 + HSO4– ⇄ CH3NH3+ + SO42– A) CH3NH2; CH3NH3 + B) CH3NH2; SO42– C) HSO4–; CH3NH3+ D) HSO4–; SO42– E) HSO4–; H3O+ ANS: D 38. What is the pH of a buffer solution where [HA] = [A–]? a. pH = 1 b. pH = Ka c. pH = pKa d. pH = pOH e. pH = 7.0 ANS: C 39. A concentration cell is constructed by using the same half-reaction for both the cathode and anode. What is the value of Ecell for a concentration cell that combines silver electrodes in contact with 0.10 M silver nitrate and 0.00003 M silver nitrate solutions? A) +0.21 V b) +0.59 V c) +0.80 V d) –0.21 V e) +1.01 V ANS: A 40. Given the initial rate data for the reaction A + B → C, determine the rate expression for the reaction. [A] (mol/L) [B] (mol/L) rate(mol/L⋅s) 0.0344 0.160 2.11 × 10–2 0.0516 0.160 3.17 × 10–2 0.0344 0.272 6.10 × 10–2 A) Rate = 3.84[A]x[B] B) Rate = 24[A]x[B]2 C) Rate = 111[A]2x[B] D) Rate = 189[A]2x[B] E) Rate = 0.285 [B]2 ANS: B 41. The rate of reaction nitrogen monoxide and hydrogen is 0.25236 mols/h What is the rate of reaction in mols/s? 2NO + 2H2  N2 + 2H2O A) 2.5 x 10 B) 9.08 x10 C) 3.6 x 103 D) 7.01 x 10-5 E) 3.96 -1 2 ANS: D 42. The following figure shows an uncatalyzed reaction path (dashed line). Which of the other reaction paths shows the effect of a catalyst? A. solid line B. dotted line C. gray line D. double line E) All of them ANS: B 43. The decomposition of formic acid follows first-order kinetics. HCO2H(g) → CO2(g) + H2(g) The half-life for the reaction at 550°C is 24 seconds. How many seconds does it take for the formic acid concentration to decrease by 87.5%? A) 24 s B) 0.042 s C) 4.6 s D) 48.8 s E) 12.2 s ANS: C 44. For the second-order reaction below, the initial concentration of A is 1.00 M. If the concentration of A is reduced to 0.43 M after 75 seconds, what is the rate constant? 2A → B rate = k [A]2 A) 5.2 × 10−4 L/mol⋅s B) 5.7 × 10−3 L/mol⋅s C) 7.6 × 10−3 L/mol D) 1,1 × 10−2 L/mol⋅s E) 1.8× 10−2 L/mol⋅s ANS: E 45. Which of the following statements regarding the equilibrium constant is correct? A) When K >> 1, the concentration of products is much smaller than the concentrations of reactants at equilibrium. B) When K > 1, the products and reactants come to equilibrium rapidly. ANS: D 46. Which of the following is true for a chemical reaction at equilibrium regarding the concentration of products? a. They will not change because there are no more reactants. b. They will not change because the limiting reagent is gone. c. They will not change because this is a constant for each reaction. d. They will not change because the forward and reverse rates are equal. e. They will change continually because of reversibility ANS: D 47. The forward rate constant, kf, and reverse rate constant, kr, for a chemical reaction are not equal. Which of the following must be true? a. The reaction will be unable to achieve equilibrium. b. kf and kr will become equal as equilibrium is approached owing to concentration changes. c. kf and kr will become equal as equilibrium is approached owing to temperature changes. d. kf and kr will remain unequal but the rates will become equal owing to concentration changes. e. kf and kr will remain unequal but the rates will become equal owing to temperature changes. ANS: D 48. The equilibrium constant for the formation of hydrogen iodide from hydrogen and iodine is 45.0 at a certain temperature. H2(g) + I2(s) 2 HI(g) Which of the following is true regarding this equilibrium? I. The reaction is product favored. II. The reaction is reactant favored. III. Equilibrium lies to the right. IV. Equilibrium lies to the left. a. I and III b. I and IV c. II and III d. II and IV e. None are true, as the concentrations of reactants and products are essentially the same. ANS: A 49. The reaction of bromine gas with chlorine gas, shown here, has a Kp value of 7.20. If a closed vessel was charged with the two reactants, each at an initial partial pressure of 0.500 atm, what would be the equilibrium partial pressure of BrCl(g)? Br2(g) + Cl2(g) ⇄ 2BrCl(g) a. 1.9 atm b. 1.4 atm c. 0.84 atm d. 0.29 atm e. 0.57 atm 50. Solutions of potassium salts of the acids in the following table are prepared with an initial concentration of 0.300 M. Which solution will have the highest pH and be the most basic? Acid pKa HA 3.00 HB 5.00 HC 8.00 HD 9.00 HE 12.00 A) KA B) KB C) KC D) KD E)KE ANS: E 51. A solution of potassium hydroxide prepared in the lab, has a concentration of 1x10-11. What is the pH A) 1.0 x 10–3 B) 3.0 C) 11.0 D) –11.0 E) 10-11 ANS: B 52. What is the concentration of [OH–] in a 0.20 M methylamine solution? (The Kb value for this base is 4.4 x 10–4.) A) 2.2 x 10–4 M B) 9.4 x 10–3 M C) 4.4 x 10–5 M D) 4.4 x 10–4 M E) 4.0 M ANS: B 53. Which one of the following salts forms aqueous solutions with pH = 7? A) KF B) KNO3 C) KH2PO4 D) K2SO3 E) KClO ANS: B 54. A 100.0 mL solution of 0.30 M ammonium chloride was titrated with 0.50M potassium hydroxide. What was the pH of the solution after 30.0 mL of the KOH solution were added? The Kb of ammonia is 1.76 x 10–5. A) 9.25 B) 5.02 C) 4.75 D) 8.98 E) 11.22 ANS: A 55. The solubility of PbBr2 is 0.427 g per 100.0 mL of solution at 25°C. Determine the value of the solubility product constant for this strong electrolyte. Lead(II) bromide does not react with water. a. 5.4 x 10–4 b. 2.7 x 10–4 c. 3.1 x 10–6 d. 1.6 x 10–6 e. 6.3 x 10–6 ANS: E 56. The solubility product for Al(OH)3 is written as __________. a. d. b. e. c. ANS: A 57. When sodium chloride is added to a saturated solution of lead(II) chloride, some of the lead(II) chloride precipitates. This phenomenon is called __________ a. the common ion effect. b. selective precipitation. c. supersaturation. d. a solubility anomaly. e. deionization. ANS: A 58. Determine ΔS°rxn for H2(g) + I2(g)⇄ 2HI(g) given the following information. Substance S°(J/mol · K) H2(g) 130.58 I2(g) 116.73 HI(g) 206.3 A) –41.10 J/mol · K B) –165.29 J/mol · K C) +398.75 J/mol · K D) +165.29 J/mol · K E) +41.10 J/mol · K ANS: D 59. Which of the following must be true for a spontaneous exothermic process? A) only that ΔSsys < 0 B) only that ΔSsys > 0 C) both ΔSsys < 0 and the magnitude of ΔSsys < the magnitude of ΔSsurr D) both ΔSsys < 0 and the magnitude of ΔSsys > the magnitude of ΔSsurr E) either ΔSsys > 0 or ΔSsys < 0 and the magnitude of ΔSsys < the magnitude of ΔSsurr ANS: E 60. A voltaic cell is constructed based on the reaction of Br -(aq) with Cl2(g) producing Cl -(g) and Br2(l ), with platinum serving as inert electrodes. Identify the correct cell diagram. a. Br2( ) | Br -(aq) || Cl2(g) | Cl-(aq) b. Pt(s) | Cl2(g) | Cl-(aq) || Br2( ) | Br -(aq) | Pt(s) c. Pt(s) | Br -(aq) | Cl2(g) || Br2( ) | Cl-(aq) | Pt(s) d. Pt(s) | Br -(aq) | Br2( ) || Cl2(g) | Cl-(aq) | Pt(s) e. Pt(s) | Br2( ) | Br -(aq) || Cl2(g) | Cl-(aq) | Pt(s) ANS: D 61. The unit of charge, the coulomb (C), is defined as ________ A) 1 A. B) 1 mole of electrons per second. C) 1 A x s D) 96,500 C/s. E) 1 mole of electrons. ANS: C 62. Phosphoric acid is a triprotic acid, ionizing in the following sequential steps: H3PO4 + H2O ⇄ H2PO4– + H3O+ Ka1 H2PO4– + H2O ⇄ HPO42– + H3O+ Ka2 HPO42– + H2O ⇄ PO43– + H3O+ Ka3 What is the Kb expression for the base, sodium phosphate? a. Ka3 b. 1/Ka3 c. Kw/Ka3 d. Kw x Ka3 e. Kw/ Ka1x Ka2 xKa3 ANS: C 63. Which indicator is most appropriate for the titration of acetic acid with NaOH? The Ka for CH3CO2H is 1.8 × 10−5. a. methyl red (pH 5) b. bromthymol blue (pH 7) c. phenolphthalein (pH 9) d. Both methyl red and bromthymol blue are suitable. e. All three indicators are suitable. ANS: C 64. What volume of 0.2045 M NaOH is necessary to titrate 50.00 mL of 0.1177 M acetic acid? a. 12.02 mL b. 18.01 mL c. 23.77 mL d. 28.78 mL e. 86.87 mL ANS: D 65. At 0 K, the entropy of a perfect crystal is A) >0. B) =0. C)