Exam 3-solutions-2

Exam 3-solutions-2 - Version 292 Exam 3 laude(51635 This...

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Version 292 – Exam 3 – laude – (51635) 1 This print-out should have 40 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 6.0 points SulFuric acid is a remarkably versatile mate- rial but it can’t do everything. Which oF the Following is not a common use? 1. oxidizing agent 2. reducing agent correct 3. acidifcation 4. dehydrating agent Explanation: The highly oxidized sulFate anion serves as agoodoxidizingagentinhighconcentrations. 002 6.0 points The ’a’ term For this question is 1. As e c on d - o rd e rr e a c t i onh a sar a t ec - stant oF 1 . 25 M - 1 · s - 1 .I Fth ein i t ia lr ea c tan t concentration is 1.0 M, calculate the time re- quired For 90% reaction. 1. 1.3 s 2. 0.13 s 3. 0.89 s 4. 17 s 5. 7.2 s correct Explanation: 003 6.0 points The overall reaction: NO 2 ( g )+CO( g ) -→ CO 2 ( g )+NO( g ) has an empirically determined rate law with as ing leb imo lecu larco l l is ionthatdoesn ’tin- volve CO. IF k =2 . 0 × 10 2 M - 1 · s - 1 ,[NO 2 ] =0 .3Mand[CO ] =0 .1M ,wh a ti sth e observed rate? 1. 18 M · s - 1 correct 2. 6M · s - 1 3. 1 . 8M · s - 1 4. 60 M · s - 1 Explanation: rate = k · [NO 2 ] 2 . 0 × 10 2 M - 1 · s - 1 · [0 . 3] 2 =1 . · s - 1 004 6.0 points Which oF carbon’s allotropes conduct elec- tricity? I) graphite II) Fullerene III) diamond 1. IandIII 2. IandIIon ly correct 3. Ion 4. II and III 5. I, II and III 6. III only 7. II only Explanation: Graphite and Fullerene are both electrically conducting on account oF their sp 2 hybridiza- tion. Diamond does not conduct electricity. 005 6.0 points Consider the reaction mechanism below: Step Reaction 1N O 2 2 NO 2 ±+± 2N O 2 NO 2 ± overall 2NO 2 2 2NO 2 ±
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Version 292 – Exam 3 – laude – (51635) 2 Which species is a catalyst and which is an intermediate, respectively? 1. none, NO 2 F 2. NO 2 F, F 3. none, F correct 4. NO 2 ,NO 2 5. NO 2 ,F Explanation: The reactants that precede the slowest for- ward step will appear in the rate law for a reaction. 006 6.0 points What is the name of the following molecule? OH H 3 C O 1. 1-methyl-1-phenyleth-2-anoic acid 2. 2-phenylpropanoic acid correct 3. 1-propanoylbenzene 4. 2-methyl-2-phenylethanoic acid Explanation: Carbon number starts at the carboxyl car- bon on account of its greater priority and the phenyl function group is attached to the sec- ond carbon in that three carbon chain. 007 6.0 points What is the average current generated in the Cu(s) | Cu 2+ (aq) || Fe 3+ (aq) | Fe(s) electrochemical cell if 50 g of Cu(s) are used up in a 24 hour period? Cu 2+ +2 e - Cu E red =+0 . 22 V 3+ +3 e - E red = - 0 . 04 V 1. 111.85 amp 2. 13.00 amp 3. 2.64 amp 4. 1.76 amp correct 5. 42.17 amp Explanation: m Cu =50g t =24h The half equation of interest is Cu(s) Cu 2+ (aq) + 2 e - Find the moles of Cu dissolved: (50 g Cu) 1molCu 63 . 546 g Cu =0 . 786832 mol Cu Find the amount of charge carried by the electrons: (0 . 786832 mol Cu) × 2mo le - × 96485 C 1mo l e - =1 . 51835 × 10 5 C Find the average current in 24 hours: Colombs = amp × second amp = Coulomb second = 1 . 51835 × 10 5 C 24 h × 1h 60 min × 1m in 60 s . 75735 C / s=1 . 75735 A 008 6.0 points Which of the following gemstones was used for ±reproo±ng until it was discovered to be a potent carcinogen?
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This note was uploaded on 08/24/2011 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas.

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Exam 3-solutions-2 - Version 292 Exam 3 laude(51635 This...

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