Chemistry 201 e.edu



Chemistry 123 Spring 2002 Oregon State University

Exam 2 May 23, 2002 Dr. Richard Nafshun

DO NOT OPEN THIS EXAM UNTIL INSTRUCTED.

CALCULATORS ARE NOT TO BE SHARED.

Instructions: You should have with you several number two pencils, an eraser, your 3" x 5" notecard, and your University ID Card. You may use a TI-25X Solar or TI-30XA calculator if you wish. If you have notes with you, place them in a sealed backpack and place the backpack OUT OF SIGHT. Or place the notes directly on the table at the front of the room.

Fill in the front page of the Scantron answer sheet with your last name, first name, middle initial, and student identification number. Leave the class section number and the test form number blank.

This exam consists of 19 multiple-choice questions and 5 open-ended questions. Each question has four points associated with it—except open-ended questions 1 and 3 (six points each). Select the best multiple-choice answer by filling in the corresponding circle on the rear page of the answer sheet. If you have any questions before the exam, please ask. If you have any questions during the exam, please raise your hand to attract the attention of a proctor. The proctor will come to you. Open and start this exam when instructed. Present your ID card when submitting the exam. Place your open-ended portion of this exam in the appropriate stack. Place your 3" x 5" notecard in the appropriate stack. You may keep the multi-choice portion of this exam, so please mark the answers you selected on it.

F = 96,500 Coulombs/mole e-

1. The oxidation number of manganese in NaMnO4 is:

(A) +2.

(B) +3.

(C) +5.

(D) +7.

(E) +9.

2. Consider the reaction Zn (s) + Cu2+ (aq) → Zn2+ (aq) + Cu (s). The species being oxidized is:

(A) Zn (s).

(B) Cu2+ (aq).

(C) Zn2+ (aq).

(D) Cu (s).

3. Consider the unbalanced reaction C6H12O6 (aq) + V5+ (aq) → V2+ (aq) + CO2 (g) that occurs in acid. The species being reduced is:

(A) C6H12O6 (aq).

(B) V5+ (aq).

(C) V2+ (aq).

(D) CO2 (g).

4. In lecture we observed the reaction of a lead metal strip placed in aqueous CuSO4 (aq); Cu (s) is formed—the half reactions can be found in the Table provided. The oxidizing agent is:

(A) Pb (s).

(B) Pb2+ (aq).

(C) Cu (s).

(D) Cu2+ (aq).

(E) SO42- (aq).

5. The calculated cell potential (voltage) for the 2 Li (s) + Cu2+ (aq) → 2 Li+ (aq) + Cu (s) is:

(A) + 0.340 V.

(B) + 2.700 V.

(C) + 3.040 V.

(D) + 3.380 V.

(E) + 5.906 V.

6. A student provides a current of 3.25 amps through an aqueous solution of Al(NO3)3 for 5.00 hours. The voltage is such that aluminum metal is deposited at the cathode. The mass of aluminum deposited is:

(A) 0.0909 g.

(B) 1.54 g.

(C) 2.73 g.

(D) 2.73 g.

(E) 5.45 g.

7. Consider Co2+ (aq), Pb2+ (aq), Cu2+ (aq), Ag+ (aq), and Li+ (aq). The strongest oxidizing agent is:

(A) Co2+ (aq).

(B) Pb2+ (aq).

(C) Cu2+ (aq).

(D) Ag+ (aq).

(E) Li+ (aq).

8. When a beta particle is emitted,

(A) An electron is converted to a helium nucleus.

(B) A gamma ray is released.

(C) Two gamma rays are released.

(D) A proton is converted to a neutron.

(E) A neutron is converted to a proton.

9. Am-243 decays to produce a beta particle and ______________________.

(A) Cm-243.

(B) Am-242.

(C) Am-245.

(D) Np-243.

(E) Np-241.

10. Ra-226 decays to produce an alpha particle and ______________________.

(A) Rn-222.

(B) Rn-226.

(C) Fr-226.

(D) Fr-222.

(E) Po-222.

11. A student obtains a sample of Sr-90 (t1/2 = 28.5 years) containing 50,000 atoms.  How long will it take for the sample to decay to 25,000 atoms of Sr-90? 

(A) 90 years.

(B) 45 years.

(C) 28.5 years.

(D) 14.25 years.

(E) 57.0 years.

12. A student obtains a sample of Sr-90 (t1/2 = 28.5 years) containing 50,000 atoms.  How long will it take for the sample to decay to 1880 atoms of Sr-90? 

(A) 135 years.

(B) 151 years.

(C) 162 years.

(D) 302 years.

(E) 1880 years.

13. Consider U-238. U-238 has: 

(A) 90 protons and 238 neutrons.

(B) 90 protons and 148 neutrons.

(C) 92 protons and 146 neutrons.

(D) 119 protons and 119 neutrons.

(E) 235 protons and 238 neutrons.

14. Considering nuclear chemistry, which of the following statements is false?

(A) An example of nuclear fusion is 11H + 21H → 32He.

(B) An example of nuclear fission is 10n + 23592U → 13752Te + 9740Zr + 2 10n.

(C) The half-life is the time required for a sample to decay to one-half its original amount.

(D) Gamma radiation has a mass of –1.

(E) Radioactive decay is a first-order decay process.

15. Considering the carbon cycle and radiocarbon dating, which of the following statements is false?

(A) The carbon-14 concentration in fossils is less than the carbon-14 concentration in you.

(B) Carbon-14 in living organisms does not undergo decay.

(C) Carbon-14 can be used to date specimens previously in the carbon cycle.

(D) Carbon-14 is generated in the upper atmosphere.

16. True or False. The energy released from the combustion of one mole of octane is greater than the energy released from the fission of one mole of uranium–235.

(A) True.

(B) False.

17. True or False. mer- and fac- isomers exist for [CoCl3F3]3-.

(A) True.

(B) False.

18. True or False. Ethylene diamine tetraacetic acid (edta) is a hexadentate.

(A) True.

(B) False.

19. Which of the following is NOT a Lewis base is the presence of a transition metal ion?

(A) Cl-.

(B) F-.

(C) H2O.

(D) NH3.

(E) CH4.

Chemistry 123 Spring 2002 Oregon State University

Exam 2 May 23, 2002 Dr. Nafshun

Student's Name ______________________________________________________________________

ID Number ______________________________________________________________________

|Recitation Instructor |Rob |Young |Jan |Jian |Vaz Williams |Christopher Walsh |John Hunt |

|(Circle One) | | | | | | | |

| |Pat |Venu |Kaustubh |Keirsten |Ganesh |Michael | |

|Recitation Day (Circle One) T W R |Recitation Time (Circle One) 8am 9 10 11 Noon 1pm 2 3 4 5 |

1.[6] Consider: 2 Al (s) + 6 H+ (aq) → 2 Al3+ (aq) + 3 H2 (g).

(a) Which species is gaining electrons? ______________

(b) How many electrons are being transferred for the process shown? ______________

(c) Which species is being reduced? ______________

(d) Which species is being oxidized? ______________

(e) Which species is the reducing agent? ______________

(f) Which species is the oxidizing agent? ______________

2.[4] Sketch our "General Chemistry Battery" [Zn (s) + Cu(NO3)2 (aq) → Zn(NO3)2 (aq) + Cu (s)]. Indicate all components and show the flow of electrons and ions.

[Turn over for questions 3-5]

3.[6] Balance the following unbalanced redox equation in acid:

Cr2O72- (aq) + Cl- (aq) → Cr3+ (aq) + Cl2 (g)

Place your final balanced equation in the box below.

4.[4] A student obtains a sample of C-11 (t1/2 = 20.39 minutes) containing 2,000 atoms.  How long will it take for the sample to decay to 312 atoms of C-11?

5.[4] Sketch the cis- and trans- isomers for [CoBr2F4]3- and identify each as being polar or non-polar.

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|Polar or non-polar? _____________ |Polar or non-polar? _____________ |

|cis-[CoBr2F4]3- |trans-[CoBr2F4]3- |

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