chem215-exam01-s2011[1] - Exam number: CHEM 215, General...

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Unformatted text preview: Exam number: CHEM 215, General Chemistry II Department of Chemistry and Biochemistry EXAM ONE, 10 Mar 2011 San Francisco State University Print your name and exam number on the Scantron form and on your green book. Print your name, SFSU ID number, select the exam-return method, and sign the certification on back cover of this exam. A periodic table, list of abbreviations, and physical constants, including standard reduction potentials, are included with this exam. Any stand-alone calculator may be used. Use of any other materials during the exam will be considered to be an act of cheating and will be reported to the Student Disciple Office. All personal items other than a calculator and writing instruments must be put inside a pack or other container (this includes textbooks, lab manuals, notes, cell phones, iPods, etc.). Unless stated otherwise, assume that strong electrolytes are 100% ionized and all solutions are at 25 oC. The exam period is 9:35—10:50 (75 minutes). You must put your green book, with this exam and your Scantron form inside the green book, in the exam box by10:55 am. Exams will not be accepted after 10:55 am. You are responsible to check your exam for completeness! Mutiple-choice questions. This exam includes 20 multiple-choice questions worth 6 pts each. • When you have selected your answer, blacken the corresponding space on the SCANTRON answer sheet with a soft, black #2 pencil. Make a heavy, full mark, but no stray marks. If you decide to change an answer, erase the unwanted mark very carefully. • There is only one correct answer to each question. Any questions for which more than one response has been blackened will not be counted. • Your score is based solely on the number of questions you answer correctly. It is to your advantage to answer every question. • The best strategy is to arrive at your own answer to a question before looking at the choices. Otherwise, you may be misled by plausible, but incorrect, responses. Problems. This exam includes 4 problems worth a total of 80 pts. • Begin your answer to each problem on a new page in your green book, starting with the first page in the book. Write the problem number on the top of every page used to answer the problem. • Answers to numerical problems must show all steps necessary to reach the answer – no credit will be given for simple numerical answers. • Explanations must be written in complete English sentences. Poor expression will result in loss of credit. It is to your advantage to write short, concise explanations. • Your score is based upon both correct and incorrect responses. • The best strategy is to make some response to every question. If you don’t have time to finish a problem, describe the steps that would lead to the correct solution. If you believe a numerical answer is wrong, explain why it’s wrong. If your explanation is correct, you’ll get more credit than you would otherwise have received. 1. The electron in a ground-state hydrogen atom absorbs a photon of wavelength 102.6 nm. To what energy level does it move? (A) 6 (B) 5 4. In the electrolysis of dilute sulfuric acid, H2SO4, (A) reduction occurs at the anode. (B) the anode reaction is 2H+(aq) + 2e– → H2(g) (C) 4 (C) the anode reaction is 4OH–(aq) → O2(aq\\g) + 4H+(aq) + 4e–. (D) 3 (D) (Ε ) the anode reaction is 2H2O(l) → 4H+(aq) + O2(g) + 4e–. 2 2. A photon of light of 250 nm, when compared to light of wavelength 300 nm, has 5. Which electron transition is associated with the smallest emission of energy? (A) n = 2 to n = 1 (A) a lower frequency. (B ) n = 2 to n = 3 (B) a greater velocity. (C) n = 2 to n = 4 (C) higher energy. (D) n = 6 to n = 2 (D) a longer wavelength. (E) 3. What is the minimum number of 790 nm photons needed to form one 34 nm photon? (A) 0.04 (B) 1 (C) 23 (D) 24 n = 1 to n = 5 6. The existence of discrete (quantized) energy levels in an atom may be inferred from (A) atomic line spectra. (B) diffraction of electrons by crystals. (C) experiments on the photoelectric effect. (D) X-ray diffraction by crystals. (E) 25 7. The number of cis–trans isomers possible for [Pt(NH3)2Cl2] is (A) 0 (B) 2 (C) 3 (D) 4 (E) 5 8. Which complex ion has the largest number of unpaired 11. What is the E0 value for a manganese–aluminum electrons? voltaic cell? (A) CoCl64– Standard Reduction Potentials (B) FeCl63(C) Mn(CN)6 Mn2+(aq) + 2e– → Mn(s) E0 = –1.18 V 4– (D) Cr(NH3)6 (E) Al3+(aq) + 3e– → Al(s) 3+ Cu(NH3)62+ E0 = –1.66 V (A) 0.22 V (B) 2.84 V The rate equation for a chemical reaction is determined by (C) 1.42 V (A) theoretical calculations. 9. (E) (B) measuring reaction rate as a function of concentration of reacting species. (C) determining the equilibrium constant for the reaction. (D) measuring reaction rates as a function of temperature (D) 0.48 V 0.96 V 12. Which is the strongest reducing agent? (A) Hg2+(aq) (B) Cu2+(aq) (C) Zn2+(aq) (D) Hg(l) (E) Zn(s) 10. What is true in the galvanic cell in which the overall reaction is Mg(s) + Br2(l) → Mg2+(aq) + 2Br–(aq) (A) The Br2 | Br– electrode is the anode. (B) Mg2+ ions migrate towards the cathode. (C) An increase in concentration of increase the cell voltage. Mg2+ would (D) The electrons enter the magnesium electrode from the external circuit. 13. Balance the equation for the following reaction, using no fractional coefficients. ? C + ? HNO3 → ? CO2 +? NO2 + ? H2O The sum of the coefficients in the balanced equation is (A) 16 (B) 12 (C) 9 (D) 7 (E) 5 14. Which statement is true for the cell as it discharges? Zn | Zn2+(1 .0 M) || Sn2+(1.0 M) | Sn (A) The concentration of Zn2+(aq) will increase. 18. How many coulombs of electricity are required to completely convert 0.340 g of AgNO3 (FW = 169.9) into metallic Ag? (B) Electrons will flow from the tin electrode to the zinc electrode. (A) 19.3 (B) 96.5 (C) Oxidation occurs at the tin electrode. (C) 193 (D) The mass of the tin electrode will decrease. (D) 386 (E) 15. The same quantity of electricity is passed through 1 M solutions of HCl and of H2SO4 at different temperatures. The number of grams of hydrogen evolved from the H2SO4 solution, compared to that evolved from the HCl solution, is (A) (B) (C) (D) (E) twice as much. one half as much. the same. a function of the molarity of the solutions. a function of the temperature of the solutions. 19. 48.3 In the chemical reaction, Zn(s) + CuSO4(aq) → ZnSO4(aq) + Cu(s), (A) metallic zinc is the reducing agent. (B) metallic zinc in reduced. (C) copper ion is oxidized. (D) sulfate ion is the oxidizing agent. 16. What geometry does [Co(en)2(H2O)2]3+ exhibit? 20. Nickel is a transition element and has a variable valence. Using a nickel salt, 2 F (faradays) plate out 39.2 g of nickel. What ions are in the solution of this salt? (A) octahedral (B) square planar (C) tetrahedral (A) Ni+. (D) linear (B) Ni2+. (C) Ni3+. (D) Ni2/3+. 17. Which equilibrium can be described as an acid–base reaction using the Lewis acid–base definitions, but not using the Brønsted–Lowry definitions? (A) 4 NH3 + Cu(H2O)42+ (B) 2 NH3 +H2SO4 ! " ! " Cu(NH3)42+ + 4 H2O 2 N H 4+ + S O 42– (C) Fe(H2O)63+ + H2O ! " H3O+ + Fe(H2O)5(OH)2+ (D) NH3 + CH3COOH ! " CH3COO– + NH4+ (E) ! " H3O+ + CH3COO– H2O + CH3COOH (Problems begin on the next page.) . Begin your answer to each problem on a new page in your green book, starting with the first page in the book. Write the problem number on the top of every page used to answer the problem. Answers to numerical problems must show all steps necessary to reach the answer – no credit will be given for simple numerical answers. Explanations must be written in complete English sentences. Poor expression will result in loss of credit. It is to your advantage to write short, concise explanations. Problem 1 (24 pts) Prepare a diagram that illustrates the key components of either a proton-exchange-membrane or a solid-oxide fuel cell, for which the overall cell reaction is 2 H2(g) + O2(g) → 2 H2O(l). Include the following information: a) identify the fuel cell as a proton-exchange-membrane or a solid-oxide fuel cell b) identify each component by its electrochemical term c) describe each component’s primary function d) show the direction of electron flow e) write a balanced half-reaction for each electrode f) show the direction of ion flow and identify the ion that is moving Problem 2 (20 pts) If the Ecell of the following cell is 1.05 V at 25 oC, what is the pH in the anode compartment? Pt(s) | H2(1.00 atm) | H3O+(aq) | | Ag+(0.450 M) ) | Ag(s) Problem 3 (24 pts) Draw orbital-energy splitting diagrams and use the spectrochemical series to show the orbital occupancy for each of the following (assume that H2O is a weak-field ligand): (a) [MoCl6]3− (b) [Ni(H2O)6]2+ (c) [Ni(CN)4]2− Problem 4 (12 pts) A complex, ML62+, is violet. The same metal forms a complex with another ligand, Q, that creates a weaker field. What color might MQ62+ be expected to show? Explain. BE SURE TO ENTER YOUR PERSONAL INFORMATION ON THE BACK COVER OF THIS EXAM! PUT YOUR MARKED SCANTRON FORM AND THIS EXAM INSIDE YOUR GREEN BOOK. TURN IN THE EXAM/SCANTRON FORM/GREEN BOOK AND ALL SCRAP PAPER TO YOUR INSTRUCTOR. Surname (family name) put the first letter of your surname in the big box; continue with one letter per box First (given) name: SFSU ID number: MC: / 20 (6 pts each; 120 pts total) problem #1 / 24 points problem #2: / 20 points problem #3: / 24 points problem #4: / 12 points Total / 200 points Sign your name in one of the boxes below to indicate how you want to have your exam returned after grading. My signature certifies that the work submitted for this exam has been performed without assistance from or collaboration with any other person. 1 2 pick up from a pile of graded exams made available * to all students to examine, at the beginning of a CHEM 215 class meeting forward to a CHEM 216 instructor for distribution during a CHEM 216 class meeting * Instructor: 3 held for pick-up during office hours *My signature in the box indicates that I voluntarily waive my privacy and confidentiality rights provided by the Family Educational Rights and Privacy Act. ...
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This note was uploaded on 09/23/2011 for the course CHEM 215 taught by Professor Staff during the Spring '11 term at S.F. State.

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