Practice Final for Chem 104

Transcription

1 Practice Final for Chem 104 These questions cover the material that will be covered on the Final Exam. The distribution of the questions is about the same as the Final Exam. The forms of the questions and specific questions will not appear on the Final Exam. There may be material on the Final Exam that does not appear here. Do not assume that if you can work these problems, you will also be able to do all of the problems on the actual exam. Use this Practice Test only as a tool to see which areas you don't remember or understand. You will need to find a sheet of Useful Equations and the structures of the 20 protein derived Amino Acids in another link.. This will all be provided for you on the actual Final Exam. There are 60 questions on the final. A compound decomposes through the following unbalanced reaction in acidic media: MnO 2 (s) MnO 4 - (s) + Mn 2+ (s) Balance this reaction and use the information to answer the following three (3) questions. 1. What is the reducing agent? a) H + b) H 2 O c) MnO 2 d) MnO 4 - e) Mn What is the coefficient of H + in the balanced reaction? a) 0 b) 2 c) 4 d) 8 e) How many electrons are transferred in the balanced reduction half-reaction? a) 1 b) 2 c) 3 d) 4 e) 5 If you have solid iron and iodine (in the form of electrodes) and aqueous solutions of 1.0 M Fe 2+ and 1.0 M I -, a galvanic cell can be constructed. Use this to answer the next three (3) questions. Fe e - Fe (s) ξ o = V I e - 2 I - ξ o = 0.54 V 4. Indicate which of the reactions shown below will take place at the cathode. a) Fe(s) + I 2 (s) Fe I - b) Fe 2+ (aq) + 2 e - Fe(s) c) Fe (s) Fe e - d) I 2 (s) +2e - 2I - (aq e) 2I - (aq) I 2 (s) + 2e -

2 5. Calculate the voltage of this cell: a) V b) V c) V d) +1.0 V e) V 6. If the concentration of I - were changed to 2.0 M, the voltage of this non-standard cell would be: a) +1.0 V b) c) V d) +1.3 V e) V 7. For how many hours would you have to pass a current of 20 amps through molten CaCl 2 to produce 1 kg of metallic calcium? (formula weight = g/mol). a) 8.3 hrs b) 16.7 hrs c) 33.4 hrs d) 66.8 hrs e) hrs The following reaction takes place in the gas phase: 2 H 2 (g) + 2 NO (g) 2 H 2 O (g) + N 2 (g) Experiments were carried out to determine the initial rate of the reaction under different initial conditions: 8. The reaction is: Experiment [NO] i [H 2 ] i Initial rate (M/s) a) First order in NO and first order in H 2 b) First order in NO and fourth order in H 2 c) Fourth order in NO and first order in H 2 d) First order in NO and second order in H 2 e) Second order in NO and first order in H 2 9. A certain first order reaction is 25% complete in 80 s. What are the values of the rate constant and half-time of the reaction? a) 4.3 x 10-3 s -1 and 160 s b) 3.6 x 10-3 s -1 and 192 s c) 1.73 x 10-3 s -1 and 401 s d) 1.50 x 10-3 s -1 and 462 s e) 4.1 x 10-3 s -1 and 175 s

3 10. The dimerization of butadiene was studied at 500 K. 2C 4 H 6 (g) C 8 H 12 (g) The following results were obtained and plotted in three different ways: time (s) [C 4 H 6 ] (M) x x x x 10-2 This reaction is: a) zero order with k = 1.53 x 10-6 M s -1 b) 1st order with k = 1.53 x 10-6 s -1 c) 2nd order with k = 1.53 x 10-6 M -1 s -1 d) 1st order with k = 1.40 x 10-4 s -1 e) 2nd order with k = 1.40 x 10-2 M -1 s -1

4 Use the following structure to answer the next two questions: 11. Predict the bond angle about each of the labeled atoms in the molecule I II III IV a) 109 o 120 o 120 o 109 o b) 120 o 120 o 120 o 90 o c) 109 o 120 o 120 o 180 o d) 109 o 109 o 109 o 109 o e) 109 o 109 o 180 o 120 o 12. The hybridization of each of the marked atoms is: I II III IV a) sp 2 sp 2 sp 2 sp 2 b) sp 3 sp 3 sp 3 sp 3 c) sp 3 sp 2 sp 2 sp 3 d) sp 3 sp 2 sp 2 sp e) sp 3 sp sp 2 sp What is the major product of the following reaction?

5 14. The addition reaction above is an example of: a) halogenation b) hydrohalogenation c) hydration d) reduction e) chlorination 15. Order by increasing solubility in water: I. CH 3 CH 2 CH 2 CH 3 II. CH 3 CH 2 NHCH 3 III. CH 3 CH 2 OCH 3 IV. CH 3 CH 2 CH 2 OH a) I < II < III < IV b) II < IV < III < I c) IV < I < III < II d) I < III < II < IV e) III < II < IV < I 16. The melting point of ethylamine is lower than the melting point of ethanol because: a) Nitrogen is lighter than oxygen b) The London Dispersion Forces of ethanol are stronger than those of ethylamine. c) There are weaker intermolecular forces in ethylamine than in ethanol. d) Ethanol prefers the solid phase e) Ethylamine does not hydrogen bond but ethanol does. 17. Identify the following compound: a) acetal b) ketal c) hemi-acetal d) hemi-ketal e) ether 18. Carboxylic acids with more than 8 carbons are essentially insoluble in water because: a) the carboxyl group is not ionizable b) the carboxyl group can not form hydrogen bonds with water c) the hydrocarbon chain is hydrophobic d) they are too dense e) none of the above

6 19. The following reaction gives which product(s)? 20. The reaction shown above is of what type? a) reduction b) oxidation c) hydrogenation d) condensation e) none of the above 21. The products of the hydrolysis reaction below are:

7 22. Order the following by increasing boiling point: I dimethyl ether II ethanol III water IV dimethylamine V propane a) I < II < IV < IV < V b) III < V < IV < I < II c) V < IV < III < I < II d) V < I < IV < II < III e) V < IV < III < II < I 23. Which amino acids found in proteins have two stereocenters? a) Ile and Leu b) Asn, Gln and Tyr c) Thr and Ile d) Val, Leu, Thr e) All of the above 24. Which of the following statements is true about alpha helices and beta sheets? a) They describe the secondary structure of proteins. b) Alpha helices have 3.6 amino acids per turn. c) Beta sheets can be parallel or anti-parallel. d) Both structures are stabilized by hydrogen bonding. e) All of the statements (a-d) are true. 25. Shown below is the structure of histidine at ph = 7.0. The pka values are marked. The isoelectric point of histidine is: a) ph = 5.44 b) ph = 3.94 c) ph = 7.6 d) ph = 7.0 e) ph = 2.98

8 26. Which is the structural formula for the predominant form of lysine at ph = 8.5, given that the pka for the -COOH = 2.18, the pka of the -NH 3 = 8.95 and the pka of the side chain = Calculate the ph of a 0.25 M solution of triethylamine (K b = 6.00 x 10-4 ). a) ph = 1.91 b) ph = 10.2 c) ph = 1.61 d) ph = 13.4 e) ph = When 50 ml of a 0.25 M chloroacetic acid solution (K a = 1.4 x 10-3 ) is titrated with M NaOH, how many ml of base will need to be added to reach the equivalence point in the titration? a) 12.5 ml b) 25.0 ml c) 50.0 ml d) 62.5 ml e) 31.2 ml Consider the titration curve of glutamic acid for the next three questions.

9 29. At what point is the ph = pka of the -NH 3 group? a) G b) B c) A d) F e) E 30. The major species in solution at point C is: 31. What is the isoelectric point of glutamic acid? a) 0.5 b) 2.2 c) 3.1 d) 4.2 e) How many different monochlorination products are formed in the reaction shown below? a) 1 b) 2 c) 3 d) 4 e) Name the structure shown below: a) 2-chloro-3-isopropyl-5-methylheptane b) 2-chloro-3-isopropyl-5-methylhexane c) 5-chloro-4-isopropyl-2-methylheptane d) 5-chloro-4-isopropyl-2-methylhexane e) none of the names (a-d) are correct

10 34. Which of the following pairs of compounds represent a pair of geometric (cis / trans) isomers? Use the structures below for the next two questions. 35. Which of these structures are enantiomers? a) III and IV b) I and IV c) I and II d) II and IV e) II and III 36. Which of the structures is/are meso compounds? a) I b) II c) III d) IV e) more than one 37. Which acid or base, when mixed with its conjugate, would make for a good buffer at ph 10.5? K a (HOC 6 H 5 ) = 1.6 x K a (HOCl) = 3.5 x 10-8 K b (CH 3 NH 2 ) = 4.4 x 10-4 a) HClO 4 b) HOC 6 H 5 c) HOCl d) CH 3 NH 2 e) NaOH

11 38. What is the ph of a solution made from 500 ml of 1.00 M HC 2 H 3 O 2 and 1000 ml of M C 2 H 3 O 2 - after 80.0 ml of M NaOH is added? (K a of HC 2 H 3 O 2 is 1.8 x 10-5 ) a) b) c) d) e) Use the following titration curve to answer the next three (3) questions. 39. What type of titration does this curve represent? a) weak acid (monoprotic) by strong base b) weak acid (diprotic) by strong base c) weak acid (triprotic) by strong base d) weak base (dibasic) by strong acid e) strong acid (diprotic) by strong base 40. If point B has a ph of 1.85, and point D has a ph of 7.19, what is the concentration of the major ph-determining species present at point C? (Assume the 5% rule holds.) a) 1.41 x 10-2 M b) 3.02 x 10-5 M c) 6.46 x 10-8 M d) 6.21 x M 41. If 200 ml of 0.4 M titrant were added to reach point E, and the total volume at point E is 350 ml, what was the initial concentration of the ph-determining species at point A? a) M b) M c) M d) M e) M 42. Suppose that this curve represents the titration of 100 ml of 0.1 M H 2 SO 3 by 0.1 M NaOH. Calculate the ph at point E, given that K a2 = 6.5 x a) 4.09 b) 7.50 c) 8.66 d) 9.85 e) 10.1

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