third_exam_ - Mill—19m A r; .. Department of Chemistry...

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Unformatted text preview: Mill—19m A r; .. Department of Chemistry " 1.13510 1 Summer Session II July 31, 2000 Course: Chemistry 1120 Third Examination NAME INSTRUCTIONS 1. Write your name and # on this page, and on the answer (Scantron) sheet. 2. Use the examination pages and the blank scrap page to work out your answers. 3. Foreach of the 25 questions, indicate the correct answer on the Scantron Vwith a #Zpencil. Each question is worth FOUR points. A non programmable, non graphic calculator may be used for this exam. ' ‘ V Answers will be posted on the notice board opposite toRoom 324, St. Albert Hall. 4. in the examination questions, scrap page, and the Scantron sheet. 5. You will have 75 MINUTES to complete the exam. PROPER CONDUCT DURING EXAMINATIONS: 1. Communication between students by any means isvprohibited. 2. Possession of any unauthorized papers is prohibited. 3. No paging devices or cell phones allowed. 4. All books, papers, and jackets should be placed in the fiont of the room. 5. I Violation of any of the above rules will result in a grade of zero. CONVERSION FACTORS , _ 1 kilogram =, 2.204, pounds ‘ p ' Avogadr’o’sNo. ‘= 6.02 x 1023 R=~0.0821Latmmor1‘K'1 ‘ ' R=V'8.314.Jmol'lK'1 ' 1 mol gas = 22.4 L gas at STP Density 0ng =' 13.5 g mL'1 Speed oflight ? 3.00 x 108 m/s Kw = 1.0 x10'14 Sp Heat H20 = 40184 J/g°c Planck’s constant = 6.63 x 10'34 J/s 1cal=4.184J 1mile=1.609km - A PERIODIC TABLE & AVFORMULA‘ SHEET ARE ATTACHED. Which statement below is true concerning an inhibitor (a negative catalyst) ? A. It lowers the energy of activation . B. It increases the change in enthalpy of the reaction. 0 It blocks the path with the lowest energy of activation for the rate deterrni ning step. C. D. It never undergoes a chemical change at any time during the reaction. The rate constant, k, for a certain chemical reaction is 2.50 x 10'3 L/mol.s at 25.0 0C, and 1.25 x 10'2 L/mol.s at 50.0 0C. What is the value of the activation energy for the reaction ? @ 51.6kJ ‘ B. 22.1 kJ c. 376ch I - . D. 45.3kJ A proposed mechanism for the catalyzed reaction I __ Step'l H202 + ‘ 1‘ , H20 + 10' Step2 H202 + 10' ffi; H20 + 02 _+ 1' Which of the following is true ? , A. The Rate Law'for the reaction is Rate = k[I-1202]2 - . _ The reaction secondvorde'r overall. v C. I; is an intermediate: D. The reaction is zero order with respect to the catalyst. Which of the following is the equilibrium law for the reaction, 302m2 + 2 NO <—=‘ so2 + 2 NOCl A. K = ([3020121m012)/([$021m0C112) 0:1 :71 n c [$02012][N012 C. K = [SOZ][NOC1]2 1@K° Given the pair of reactions shown with the equilibrium constants, ( [3021[N0C1]2 )/ ( [s020121m012) PC13 .+ C12 PC15 1K1: 2 NO + C12 ' e——-———7\ '2 NOCl What is the equilibrium constant for the, reaction, . PC15‘ +q _ "2 NO<———2 PCl3 + 2 Noel fl qr A; ‘ K1 x K2 ‘ i ‘ i ' uKzri/ n1 7 C. Kl/KZ _ D. . KZ-Kl Which of the'following is true regarding the equilibrium constant of a given reaction ? - Itcan changeas temperatme changes. ‘ B ‘ The larger the equilibrium constant, the faster the reaction; C. It increases if the concentration, of one of the products is decreased. D It may be changed by the addition of a catalyst. 7. A 0.0250 M solution ofa weak acid, HA, has a pH of 5. 13. What is the value of the acid ionization constant, Ka , for this acid ? A. 8.66 r B. 3.53 @ 2.20x10'9 D. , 1.28x10'1 8. When the salt sodium acetate, NaC2‘H302. , is dissolved in distilled water, the pH will be: A. Above 7 since NaOH is a strong base B. 'Below 7 because HC2H302 , is a weak acid. . C. Equal to 7 because Na+ is stable in solution. ‘ _ fl _ Above 7 because C2H302' is basic,being the-conjugate base of a weak acid. 9. P Which of the following salts would give an aqueous} solution that is acidic ? A. NaCl 1 . NH4C1 c. KNo3 ’ D. NaOCl 10. A solution is prepared by dissolving 0.150 moles of benzoic acid in enough distilled water to, - make 1.00 L of solution. What is the pH of this solution ? (Ka = 6.3 x 10's) A. 2.95 .. B. 5.02 @. 2.51 ' a * " ' .D. 8.98;. 11. What is the pH of a 0.05 M H2804 solution (assuming complete ionization) ? 1.0 B. —1.0 c. 1.3 ‘ p D. _'-1..3 12. A buffer solution of formic acid is made by mixing 0.75 moles of formic acid and 0.75 moles of sodium formate in 500 mL of distilled water. What is the pH of this buffer solution? (Ka= 6.07 x10'7) 6.22 is. 6.09 C. 7.00 D. 7.09 13. What is the pH of a 0.020 M KOH solution. A. 1.70 12.3 C. 7.00, . D. 5.56 14. Which of the following statements regarding bufiers is false ? A. A bufi‘er can be made from a weak base and its salt B. A bufi‘er can be made flom a weak acid and its salt @- There is no change in pH when a smallramount of strong acid is added to a buffer D. A bufi'er operates by shifting the equilibrium betweenconjugate acid-base pairs. 15. Which of the following is the weakest acid ? A. Iodic acid, pKa = 0.23 ‘ B. CYanic acid, pKa = 3.46 C. Nitrous acid, pKa = 3.15 , Propanoic acid, pKa = 4.87 16. For the reaction X 6—7—1‘ Y , Kc = 2.5 x 10‘”. Which of the following statements is true ? A. The equilibrium concentration of X is equal to Y. The equilibrium concentration of X is greater than Y. C. The equilirium concentration of X is less than Y. D. Adding more X will increase the value of the equilibrium constant. ' ' 17. Which one of the following would be basic ? i A. Grapefi'uit juice 7 a Household ammonia C.’ ‘ Carbonated water L “ D. Vinegar 18. Which of the following Correctly lists the hydrocarbons in order of decreasing boiling point ? A. 2-Methylpentane > n-HeXane > 2,3-Dimethylbutane B. _ 2,3-Dimethy1butane >2-Methylpentane >. n-Hexane @ . n-HeXane > 2-Methylpentane > 2,3-Dimethylbutane D. 2,3-Dimethy1butane > n-Hexane > 2-Methy1pentane ‘ 19. How many difl‘erent (in terms of connectivity) compounds are possible having molecular formula C3H6C12 ? ' ’ A. "1 ' q ' B. 2 (3.3 @4 20. Which of the following most accurately discribes the geometry of the methane molecule ? Tetrahedral, bond angles of 109.5 0. B. Planar triangular, bond angles of 109.5 0 C. I Tetrahedral, bond angles of 120 0. D. Planar triangular, bond angles of 120 0 21. Which of the following would have the highest melting point ? A. _ n-Hexane B. 2-Methy1pentane @ 2,2—Dimethylbutane D. 2-Methylbutane 22. Assuming that the combustion of 1 mole of propane is taking place in an excess of oxygen, which of the following is correct ? A. 3 Moles of water along with 4 moles of carbon dioxide would be formed. ‘ 3 Moles of carbon dioxide along with 4 moles of water would be formed. C. 3 Moles of water along with 4 moles of carbon monoxide would be formed. D. 3 Moles of carbon monoxide along with 4 moles of water would be formed. 23. Consider the following reaction of ethane with bromine: C2H6 ' + Br2 C2H5Br + HBr This. reaction is best described as: V A. An addition reaction B. An elimination reaction C. A combustion reaction I A substitution reaction 24. Which of the following conformations of ethane is most stable ? The staggered conformation with dihedral angle of 60 o B. The eclipsed conformation with dihedral angle of 0 ° C. The skew conformation with dihedral angle of 59 0 D. The skew conformation with dihedral angle of 1 ° 25. Which of the following must take place when ethane changes its conformation fiom the eclipsed to the staggered conformation ? A. I The breakage of the carbon-carbon bond. Retation about the carbon-carbon bond. C. Change in the hybridization of carbon from sp3 to sp2 D. Change ' " bond angles. ...
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This note was uploaded on 04/06/2008 for the course CHEM 10765 taught by Professor Brown during the Spring '08 term at St. Johns Duplicate.

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third_exam_ - Mill—19m A r; .. Department of Chemistry...

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