Exam 4-solutions

Exam 4-solutions - Version 014 Exam 4 fakhreddine (51650)...

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Version 014 – Exam 4 – fakhreddine – (51650) 1 This print-out should have 26 questions. Multiple-choice questions may continue on the next column or page – Fnd all choices before answering. 001 5.0 points ±or the reaction A B the initial concentration of [A] is 0.1 M. How much of compound [A] is left after 60 minutes if k = 4 . 2 × 10 6 s 1 ? 1. 1 . 0 × 10 1 2. 3 . 2 × 10 2 3. 9 . 8 × 10 2 correct 4. 8 . 5 × 10 2 5. 4 . 1 × 10 1 Explanation: 002 5.0 points Note: Standard potential of the electrode is its standard reduction potential. The standard potential of the Cu 2+ | Cu electrode is +0.34 V and the standard poten- tial of the cell Pb(s) | Pb 2+ (aq) || Cu 2+ (aq) | Cu(s) is +0.47 V. What is the standard potential of the Pb 2+ | Pb electrode? 1. +0.81 V 2. +0.13 V 3. 0.26 V 4. 0.81V 5. 0.13 V correct Explanation: 003 5.0 points What is the standard cell potential of the strongest battery that could be made using these half reactions? Br 2 + 2 e −→ 2 Br ±e 3+ + 3 e −→ ±e Co 3+ + e −→ Co 2+ Zn 2+ + 2 e −→ Zn E = +1 . 07 E = 0 . 04 E = +1 . 80 E = 0 . 76 1. 1.84 2. 1.04 3. 1.83 4. 2.56 correct 5. 1.03 6. 1.11 Explanation: The strongest reducing agent is Co 3+ and the strongest oxidizing agent is Zn. The stan- dard cell potential of a battery built from these species would be: E cell = E cathode E anode = 1 . 80 − − 0 . 76 = 2 . 56 004 5.0 points We know that the rate expression for the re- action 2 NO + O 2 2 NO 2 at a certain temperature is Rate = k [NO] 2 [O 2 ]. We carry out two experiments involving this reaction at the same tempera- ture, but in the second experiment the initial concentration of NO is doubled while the ini- tial concentration of O 2 is halved. The initial rate in the second experiment will be how many times that of the Frst? 1. 4 2. 1 3. 2 correct 4. 8
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Version 014 – Exam 4 – fakhreddine – (51650) 2 Explanation: [NO] 2 = 2 [NO] 1 ; [O 2 ] 2 = 1 2 [O 2 ] 1 Rate = k [NO] 2 [O 2 ] Rate 2 Rate 1 = k 2 [NO] 2 2 [O 2 ] 2 k 1 [NO] 2 1 [O 2 ] 1 = (2 [NO] 1 ) 2 1 2 [O 2 ] 1 [NO] 2 1 [O 2 ] 1 = 4 2 = 2 005 5.0 points ATTENTION!! PROVIDE YOUR AN- SWER IN YEARS AND USE THE FOL- LOWING CONVERSION: 1 year = 365.25 days Consider the reaction at 25 C 2 NO 2 2 NO + O 2 The overall rxn rate = k [NO 2 ] 2 The rate constant, k = 1 . 4 × 10 10 M 1 s 1 If 3 moles of NO 2 are initially present in a sealed 1.00 liter vessel at 25 C, what is the half-life of the reaction? 1. 56.5859 2. 53.8913 3. 41.9155 4. 51.4417 5. 23.0963 6. 37.7239 7. 34.2945 8. 113.172 9. 59.5641 10. 35.3662 Correct answer: 37 . 7239 y. Explanation:
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This note was uploaded on 07/25/2011 for the course CH 302 taught by Professor Rowland during the Spring '10 term at UT Arlington.

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Exam 4-solutions - Version 014 Exam 4 fakhreddine (51650)...

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