CHEMISTRY 102 FINAL EXAM FORM 5C

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1 CHEMISTRY 102 FINAL EXAM SECTIONS Dr. Joy Heising Directions: FORM 5C May 8, This examination consists of two parts: 40 multiple choice questions. The odd numbered questions are worth 5 points each. The even numbered questions are worth 6 points each. The total point value for the exam is 215 points plus 5 bonus points (220 total). 2. Fill out your scantron sheet. a. Do not forget to include your SIGNATURE and ID number. b. Dept = CHEM, Course No. = 102 c. If you want your scores posted, mark A under the option column 3. Use a #1 or #2 pencil for marking the scantron. Fill in the appropriate circles completely. You may write on the multiple choice questions. 4. Read each question carefully, then choose the best answer for each question. There is no penalty for guessing. 5. Standard reduction potentials are found on the envelope. DO NOT write on the envelope. 6. Selected ionization constants are found on p.11. A list of equations is found on page 13. The last sheet of this exam is scrap paper. You may detach these sheets from the exam. 7. When finished, put the SCANTRON SHEET back in the envelope and turn it in. 1 C

2 1. Calculate the standard enthalpy change for the reaction below. Fe 3 O 4 (s) + CO (g) 3FeO (s) + CO 2 (g) Hº f (kj/mol) a) 19 kj/mol b) 19 kj/mol c) 563 kj/mol d) 563 kj/mol e) 1894 kj/mol 2. A g sample of benzoic acid, C 7 H 6 O 2, undergoes complete combustion with excess O 2 in a bomb calorimeter. The temperature of the water inside the bomb rises from ºC to ºC. The combined calorimeter constant (for the container + water) is kj/ºc. What is the molar heat of combustion ( Eº rxn ) for C 7 H 6 O 2? (molar mass C 7 H 6 O 2 = 122 g/mol.) a) kj/mol b) 3025 kj/mol c) 3158 kj/mol d) 3378 kj/mol e) 3456 kj/mol 3. Which one of the following statements is CORRECT? a) When G for a reaction is negative, the reaction is nonspontaneous. b) When G for a reaction is positive, the reaction is spontaneous. c) When G for a reaction is zero, the system is at equilibrium. d) The value of G does not change as a function of the temperature. e) When H for a reaction is negative, the reaction is endothermic. 4. Consider the following diagrams: If Hº rxn is -3 kj/mol for this process, the reaction will most likely be a) spontaneous at all temperatures b) nonspontaneous at all temperatures c) spontaneous above a certain temperature only d) spontaneous below a certain temperature only e) not enough information 2 C

3 5. Which of the following changes will result in an increase in the entropy of the system? I. CH 3 OH (l) CH 3 OH (s) II. BaCl 2 (s) Ba 2+ (aq) + 2Cl - (aq) III. A popsicle melts IV. Some fans run onto Kyle field after a game V. C 3 H 8 (g) + 5O 2 (g) 3CO 2 (g) + 4H 2 O (l) a) I, II, V b) II, III, IV c) III, IV d) III, IV, V e) I, II, III, IV, V 6. Consider the following initial rate data and determine the rate law expression for: 3A + 2B 2C + D Experiment Initial [A] Initial [B] Initial rate of rxn x x 10-2 M min x x 10-3 M min x x 10-2 M min -1 a) rate = k[a][b] b) rate = k[a] 2 [B] c) rate = k[a] 2 [B] 2 d) rate = k[a] 3 [B] e) rate = k[a] 3 [B] 2 7. If a hypothetical reaction A + B + C products was found to follow the rate law: rate = k[a][c], what is the overall order of this reaction? a) zeroth b) first c) second d) third e) fourth 8. Which statement is INCORRECT? e) For zero-order behavior of reactant A, the plot of [A] vs. time would give a straight line. a) For first-order behavior of reactant A, the plot of ln [A] vs. time would give a straight line. c) For second-order behavior of reactant A, the plot of [A] 2 vs. time would give a straight line. d) The rate law expression relates rate and concentration. e) The integrated rate equation relates time and concentration. 3 C

4 9. Four of the following factors can affect the forward rate of a chemical reaction. Which one cannot affect this rate? (Note: the question refers to reaction rate, not equilibrium.) a) temperature b) presence of a catalyst c) concentration of reactants of the forward reaction d) removal of some of the products of the forward reaction e) physical state and form (e.g. fine powder vs. chunks) of reactants 10. The proposed mechanism for the decomposition of phosgene (a highly toxic gas) is: Step 1 Cl 2 (g)? 2Cl (g) fast Step 2 COCl 2 (g) + Cl (g) COCl (g) + Cl 2 (g) slow Step 3 COCl (g)? CO(g) + Cl (g) fast Overall COCl 2 (g) CO (g) + Cl 2 (g) The rate law expression must be rate =. a) k[cocl 2 ] b) k[cl 2 ] c) k[cocl][cl 2 ] d) k[cocl 2 ][Cl 2 ] 1/2 e) k[co][cl 2 ]/[COCl 2 ] 11. The correct K c expression for the decomposition of hydrogen peroxide is: 2H 2 O 2 (g)? 2H 2 O (l) + O 2 (g) a) [H 2 O][O 2 ] [H 2 O 2 ] b) [H 2 O] 2 [O 2 ] [H 2 O 2 ] 2 c) [O 2 ] [H 2 O 2 ] 2 d) [H 2 O 2 ] 2 [H 2 O] 2 [O 2 ] e) [O 2 ] 4 C

5 12. Some PCl 3 (g) and Cl 2 (g) were placed in a 2.00 L container at 200ºC and allowed to equilibrate. Subsequent analyses showed the composition of the contents of the container to be 0.25 mol PCl 3 (g), 0.46 mol Cl 2 (g), and 0.31 mol PCl 5 (g). Calculate the equilibrium constant, K c, for this reaction at this temperature. a) 5.4 b) 2.7 c) 0.37 d) 0.18 e) 6.9 x To shift the following equilibrium to the right, one should COBr 2 (g)? CO (g) + Br 2 (g) a) remove Br 2 (g) b) remove COBr (g) c) add Br 2 (g) d) add CO(g) e) none of the above 14. Consider the water-gas shift reaction at equilibrium at a certain temperature. CO (g) + H 2 O (g)? CO 2 (g) + H 2 (g) + heat Which response contains all the stresses that would shift the equilibrium so as to favor the reactants (to the left), and only those stresses? I. increase temperature at constant pressure II. decrease temperature at constant pressure III. increase the total pressure of the system IV. decrease the total pressure of the system V. add CO VI. add CO 2 a) I b) I, VI c) II, V d) I, IV, VI e) none of the above 15. Calculate the thermodynamic equilibrium constant, K, at 25ºC for a reaction for which Gº = kj per mol of reaction. R = J/mol K a) 4.16 x 10-7 b) 11.2 c) 1.03 x 10 2 d) 3.07 x 10 4 e) 2.40 x C

6 note selected dissociation constants for weak acids/bases are listed on page The K a for HF is 7.2 x The K b for its conjugate base must be a) 7.2 x 10-4 b) 7.2 x c) 1.0 x 10-7 d) 1.4 x e) 1.4 x The ph of M HCl is a) 1.27 b) 1.46 c) 7.00 d) e) You make your own vinegar by dissolving 6.00 g acetic acid in 1.00 L distilled water. What is the ph of your homemade vinegar? a) 1.00 b) 2.37 c) 2.87 d) 4.74 e) Which of the following is NOT a dissociation or hydrolysis reaction of a weak acid or weak base? a) HN 3? N H + b) CHOO - + H 2 O? CHOOH + OH - c) (CH 3 ) 2 NH H 2 O? (CH 3 ) 2 NH + H 3 O + d) HNO 3 + NaOH? NaNO 3 + H 2 O e) NH 3 + H 2 O? NH OH Calculate the ph of M KOCl. a) 3.62 b) 7.45 c) d) e) C

7 21. Which one of the following combinations is not a buffer solution? a) NH 3 - (NH 4 ) 2 SO 4 b) HBr - KBr c) HCN - NaCN d) NH 3 NH 4 Br e) CH 3 COOH NaCH 3 COO 22. What is the ph of a solution that is 0.20 M in HCN and 0.15 M in KCN? a) 7.60 b) 8.40 c) 8.80 d) 9.27 e) When a weak base is titrated with a strong acid, the ph at the equivalence point is always. a) 7 b) less than 7 c) greater than 7 d) less than 1 e) greater than What is the ph of the solution resulting from the addition of g of NaOH (s) to ml of M acetic acid, CH 3 COOH? (molar mass NaOH= 40 g/mol) a) 4.56 b) 4.92 c) 5.00 d) 5.08 e) The correct K sp expression for BiI 3 is: BiI 3 (s)? Bi 3+ (aq) + 3I - (aq) a) K sp =[Bi 3+ ][3I - ] [BiI 3 ] b) K sp =[Bi 3+ ][3I - ] 3 [BiI 3 ] c) K sp =[Bi 3+ ][I - ] 3 [BiI 3 ] d) K sp =[Bi 3+ ][I - ] 3 e) none of the above 7 C

8 26. The value of K sp for SrSO 4 is 2.8 x What is the molar solubility of SrSO 4? a) 7.6 x 10-7 M b) 5.8 x M c) 5.3 x 10-4 M d) 5.7 x 10-3 M e) 1.3 x 10-8 M 27. How is the Ksp of Ca 3 (PO 4 ) 2 related to s, the molar solubility of Ca 3 (PO 4 ) 2? a) Ksp = 4s 5 b) Ksp = 27s 3 c) Ksp = 18s 5 d) Ksp = 54s 4 e) Ksp = 108s AgCl, a slightly soluble salt, would be least soluble at 25ºC in. a) pure water b) 0.1 M CaCl 2 c) 0.1 M HCl d) 0.1 M HNO 3 e) It is equally soluble in all of the preceding substances. 29. Indicate the order in which the following solids will precipitate from solution as the concentration of I - in solution is increased. K sp (AgI) = 1.5 x K sp (AuI) = 1.6 x K sp (CuI) = 5.1 x first last a) AuI AgI CuI b) AgI AuI CuI c) CuI AuI AgI d) AuI CuI AgI e) CuI AgI AuI 30. If ml of a solution initially M in CaCl 2 is added to ml of a solution initially M in Na 2 C 2 O 4 (sodium oxalate). If the K sp value for CaC 2 O 4 is 2.3 x 10-9, Q is than K sp, and a precipitate form. a) less; will not b) less; will c) greater; will not d) greater; will e) none of the above 8 C

9 31. Reduction occurs at the in a voltaic cell and reduction occurs at the in an electrolytic cell. a) anode, anode b) cathode, cathode c) anode, cathode d) cathode, anode e) anode, salt bridge 32. How many grams of metallic nickel can be produced by the electrolysis of aqueous nickel (II) chloride, NiCl 2, with a A current for 5.00 hours? a) 1.19 g b) 1.92 g c) 2.76 g d) 3.83 g e) 7.66 g 33. When balanced, what is the total number of electrons transferred? a) 0 b) 2 c) 3 d) 5 e) 6 Cu 2+ (aq)+ Ga (s) Cu (s) + Ga 3+ (aq) (UNBALANCED) 34. What is the cell potential for a galvanic (voltaic) cell constructed by immersing a strip of copper in a 1.0 M CuSO 4 solution and a strip of cadmium in a 1.0 M CdSO 4 solution and completing the circuit by a wire and a salt bridge? a) V b) V c) V d) V e) 0.00 V Cd 2+ (aq) + 2e - Cd (s) Eº SRP = V Cu 2+ (aq) + 2e - Cu (s) Eº SRP = V note standard ½ cell potentials (Eº SRP ) are found on exam envelope (back) 35. Which of the following metals is most easily oxidized? a) Cd b) Cu c) Fe d) Ni e) Zn 9 C

10 36. Calculate the cell potential of the following voltaic (galvanic) cell at 25ºC. Ag Ag + (1.0 x 10-5 M) Au 3+ (1.0 x 10-1 M) Au a) V b) V c) V d) V e) V 37. The E in SHE represents a) element b) electricity c) electrode d) elevator e) electrolyte 38. What is Gº at 25ºC for the reaction below? (F = 9.65 x 10 4 J/V mol e - ) a) -232 kj b) 623 kj c) 313 kj d) 232 kj e) -523 kj 2Cr 3+ (aq) + 3Cu (s) 2Cr(s) + 3Cu 2+ (aq) 39. Fill in the missing member of the series: methane, ethane, propane, a) pentane b) propene c) butane d) butene e) ethyl 40. Name this compound: CH 2 C(CH 3 ) 2 a) 2,2- dimethylpropene b) 2,2- dimethylethene c) 1,1-dimethylethylene d) 2- methylpropene e) 2- methylbutane 10C

11 Selected Ionization Constants Acetic acid CH 3 COOH K a = 1.8 x 10-5 Formic acid CHOOH K a = 1.8 x 10-4 Hydrazoic acid HN 3 K a = 1.9 x 10-5 Hydrocyanic acid HCN K a = 4.0 x Hydrofluoric acid HF K a = 7.4 x 10-4 Hypobromous acid HOBr K a = 2.5 x 10-9 Hypochlorous acid HOCl K a = 3.5 x 10-8 Nitrous acid HNO 2 K a = 4.5 x 10-4 Ammonia NH 3 K b = 1.8 x 10-5 Dimethylamine (CH 3 ) 2 NH K b = 7.4 x C

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13 Some useful equations E = q + w w = -P V = - nrt R = J mol -1 K -1 E = q v E = H - P V Hº rxn = Σn Hº f prod - Σn Hº f react G = H - T S Sº = Σn Sº prod - Σn Sº react Gº rxn = Σn Gº f prod - Σn Gº f react [A] t = [A] o akt ln ([A] t /[A] o ) = - akt or log ([A] t /[A] o ) = -akt/ = akt [A] t [A] o ln(k 2 /k 1 ) = E a /R (1/T 1 1/T 2 ) K p = K c (RT) n Gº rxn = - RTlnK R = J/mol K R = L atm/mol K R = J/mol K K w = 1.00 x mol gas = 22.4 L at STP 1 Faraday = 9.65 x 10 4 Coulombs or 9.65 x 10 4 J/V mol e - Eº cell = Eº SRP(red) - Eº SRP(ox) E = Eº - (0.0592/n)log Q Gº = -nfeº cell Eº cell = (0.0592/n)log K 13C

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CHEMISTRY 102 FINAL EXAM FORM 5D

CHEMISTRY 102 FINAL EXAM FORM 5D CHEMISTRY 102 FINAL EXAM SECTIONS 529-537 Dr. Joy Heising Directions: FORM 5D May 8, 2002 1. This examination consists of two parts: 40 multiple choice questions. The odd numbered questions are worth 5