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practice_exam_i_f03_key - #5 Dr Bryan Enderle Name C Fall...

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Unformatted text preview: . #5 Dr. Bryan Enderle Name: C Fall 2003 Student ID Number: T .A. : Lab Section/Room: CHEMISTRY 2C Exam I October 17 , 2003 0 Do not open the exam until instructed to do so. Place all answers in the space provided. If you require additional space, use the back of the exam. No sharing calculators. Write your name and your T.A.’s name on each page of the exam. The exam consists of 8 pages total. The last 2 pages contain helpful information. N o programmable calculators, books, notes, or scratch paper allowed. Show all work for problems in Part B of the exam to receive full or partial credit. You will have 50 minutes to complete this exam. Answer all the questions you are sure of first, then use the remaining time for the rest. 0 UCD is an honor institution PWNT‘ fl (3 Problem Number Points Possible FIEW' TOTAL SCORE: \ D 0 (out of 100 pts) Name: T.A.’s name: Part A: Multiple Choice — Concepts and Calculations. Write the correct answer in the space provided on the first page. No partial credit will be given. 1. Estimate which of following metals is has the smallest atomic radius. a. V b. Nb c. Os d. Ta 2. Which of following has similar chemistry to aluminum? a. chromium b. vanadium c. titanium d. scandium 3. Which of following metals would oxidize first? a. Cu b. Na 0. Pb d. Sn 4. What is the oxidation reaction for a Csz/oxygen fuel cell? a. 02(g) + 2H20(1) + 4e' -) 4 OH'(aq) b. H2(g) + 4OH'(aq) 9 2H20(1) +2e' c. C2H2(g) + 2H20(l) 9 2C02(g) + 6H+(aq) + 6e' d. 2H2(g) + 02(g) -> 2H20(1) 5. What is the approximate cell potential of a storage battery? a. 12 V b. 0 V c. 2 V (1. batteries don’t have cell potentials 6. Which of the following is an incorrect chemical formula for a metal carbonyl? a. Rh(CO)5 b. Ru(CO)4 c. Mn(CO) d. Ni(CO)6 7. Predict the product at the anode when electric current is passed through a solution of K1. a. I2(s) b. K+(aq) c. H2(g) d. K(s) e. 02(g) 8. How long would it take to deposit 1.36 g of copper from an aqueous solution of copper(II) sulfate by passing a current of two amperes through the solution? a. 2060 sec b. 1.11 x 10‘5 sec c. 2570 sec d. 736 sec 6. 1030 sec 9. A possible anodic reaction that takes place during corrosion of iron is a. 02(g) + 2H20(l) + 4e‘ —>4OH_(aq). b. Fe(s) —> Fe2+ + 2e' c. 2H20(l) + 2e’ —> H2(g) + 20H(aq). d. SOz(g) + 02(g) + 26 —> SO4Z_(aq). e. 2H+ + 2e' —> H2(g). 10. In the complex [Re(en)2Br2]', a. Re has an oxidation number of +1. b. Re is a Lewis acid and CO is a Lewis base. c. Re has a coordination number of 4. d. All of the above. 6. a and b Name: T.A.’s name: 11. Which complex ion possesses the largest number of unpaired electrons? a. [CoCl4]2' b. [Cr(NH3)6]2* 0- [CU(NH3)4]2+ d. [Mn(CN)6]4+ e. [FeC16}3‘ Part B: Fill in the blank. 12. Write the correct name or structural formula for the following transition metal complexes. a [Co(CN)2(NH3)4]Br WW\ \orovmde. b. [Pt(NH3)4][CuCl4] VQQmWHWQ \ hnom \\ \MOQUQWLJYQUU c. pentacarbonylbromorhenium(lll) chloride [ 98‘ k 0 ‘5 ’8‘] Q1 '2. 13. Draw the molecules and all geometric and stereoisomers (if any) of each of the following in the space provided. Label geometric isomers cis, trans, fac, or mer. [MUC12(NH3)4] n '\N\ N“/3\ \LL of ‘n\ NW5 “5:35 NH’A Name: «7. T.A.’s name: . :7" Answers: 14. Consider the compound [Co(CN)2(NH3)4]Br W a. g a. What element acts as the cdu‘nter ion? C b. ‘ b. What is the oxidation state of cobalt? + 3 c. What is the coordination number of the cobalt? 0' (0 d. What is the hybridization of cobalt? d. A 2. S Q 3 e. What is the molecular shape of the compound? 6. Q CAYQ {)4 Q(\J(‘O\Q f. What is the electronic configuration of cobalt? f A G) g. Is the compound high or low spin? g' Qmo h- Atamajmfi‘c h. Is the compound paramagnetic or diamagnetic? i. The solution is observed to be orange in color. Would you expect [C016]Br3 to be red or yellow i. {\Q A in color? , j. Sketch the splitting pattern of the d-orbitals and fill in the electrons according to the Aufbau process. Label A0. Ck g .~ __ .21: Is. Ava aw Name: T.A.’s name: Part C: Problem Solving. Show all work to receive full or partial credit. Circle the correct answer. Include all state symbols for species when writing chemical equations. Also, write your answer with the correct number of significant figures. If you are unable to solve the first part of a multipart problem, then assume an answer and continue with the latter part showing all your work. In the case that "None of the above" is your choice, you will only receive full credit if all work and correct answers are shown. 15. The pH of a solution can be measure electrochemically with a device called a pH meter. The technique makes use of a cell in which one electrode is sensitive to the hydrogen ion concentration and the second electrode connected through a salt bridge to a calomel electrode (calomel is a common name for solid mercury (I) chloride, Hg2C12(s)). The reduction reaction reacts to form liquid mercury and chloride ion (reduction potential of 5° = +0.27 V). l‘\32®2l$\ '4‘ 1e,— ~—> ZRjQQ Jr ZU‘JCME’) b. Using the SHE as the oxidation half reaction, calculate the standard cell potential for the pH meter. SHOW YOUR WORK. 9‘93 save. 2) Am] 2:- . 2‘65sz ".27 ‘ none of the above £5 '2 6.00 \/ FBin‘EQ 2, ll LCQLWDN + Aztgxellrklmgx ”(13(9) ‘\" QCQ'LQE) Name: T.A.’s name: 15. (continued) 0. If the pressure of hydrOgen is 1.0 atm, the pH of the measured solution is 4.00, and the measured solution voltage of 0.77 V, what is the concentration (in molarity) of the chloride ions in solution? SHOW YOUR WORK. a) 1.3 x 10'13 . pit-0'?-1L O _. (log—91 @5333. at E6 7. “ 3‘3 Q Q = Gel?“ [C933 3W1 = 0 1'1 — 0 “CELQQS @632 [19:31 fifties M ._ ‘33?“ t 21 Q0 mg + %E§9~3 w “9?: ( S) . 3 *Qgcfiw (1. Knowing the. informatiOn from part c, calculate the Gibbs free energy in k]. SHOW YOUR WORK. 3 149 #149 6 449,000 d) 74 ? e) b6: —- ~V\ fi' none of "the above be: .— - LawtergCaMeiqfifl we g.) r “149,000 3 2-: —W3> k3 Name: T.A.’s name: 15. (continued) 6. Draw the complete cell diagram labeling the salt bridge, anode, cathode, and direction of electron flow. Use potassium chloride as the salt. 622%? H 2022 (33 H3 (Q) Gilead Q anode Name: T.A.’s name: Spectmchemical Series: CN'>CO>302’>en>NH3>SCE>H20>QN0'>ox2‘>0H‘>F>§CN‘>Cl'>B1-'>I‘ Constants: R = 8.3145 J J 11101 K F = 96,485 C! mol 6' R = 0.08206 L atm I mol K c = 2.9979 x 1055 m I s h = 6.626 x 10'” J 5 Equations: A = h c/ A AGO = —nFE;” AG = ‘nFEwu :9“ = WI“ Keq Ere” = E391: “ 00:92 1039 a RT AG" = AH" —TAS° AG = AG“ + RTan AG" = —RT1n Km EM = EM —‘~—#1nQ 12F Reductiun Half-Reaction H", V Acidic soluliun “3(3) - 3r: —¢ 2 I3 [am +2.36!) 0ng - 2 Hum} + 2.: —> {Mg} + H3001 +2.11% Srflu’iaqi —.- 3c —+~ 2 3.03 may: +2m Hzfigrnq') + '3 H"(aq'i + Zc' “—0 2 H3011} +1363 h'ln04'{aqb T s H‘taq) + fie —r Mn’tmn + 4 H300} +|.SI l’hfigrs) + 4I-I'tm1] + 2:! —9 Plf'taq] + 2 H30“) H.455 {This} + 2:: —~) ZCI my] H.353 Crfif'taq) -- [4 H'tnq'l + fie —> ZCIWuq! + 7 H300) +1.33 Mnflylsil + 4 H'Iaq] + 2c ~—> Mn’iml) 4- 211.1011) +1.23 800 400 0&3} ‘ 4 H‘mq} + 4': —> '2 H30“) H.229 2 It'lg'taq) + 12 H"{aq:l + Ilh: —* 1313:: + 6 HQ“) +1.2“ Bum 4- 2c “-3- 21h (alq) H.065 NU; (3.4.1) + 4 [41qu + 3c —3‘ NOIg) + 3 H300} +0.95!) Ag‘liaq] ° u —) figts] H1801.) I‘c-‘Waqi 4- a: -—> I:u3'['aq'l +I’).T.?l (Mg) - 2H'L‘aq} + 2c —> Hzihwqr +Il.fi95 [3:5] I 2 I: —) 2 I‘taq') H1535 {Tu3'ml'} 4. 20 —~ {farts} +0.34!) so} [an + 4 H‘tatp + 2c ——+ 2 H_.U('l] + 50315] +0.]? $n"[aq) 0 2e —> Snzlaq? I-I].l54 5(5) — 2 l-I‘t'aq} + 2c —~) [1380:] +[J.l4 JH‘iuqir * 'lc “"4 EH31 II sz'raq) - M —r l-‘hl;s) 0.125 51:31qu ‘ 2e —+ Sills) —lJ.l."-'.r l-‘c’faq‘; + 2:: —r Fem —II.44n Zn“taq} I an —> mm --[l.?63 Al'l‘mq'l + ".12" -——> mm 4.676 Mgl‘caq: + 2c —* Mgts) "3.356 Na‘InLI'J i c' —* Nata) Gil. (fai'ram + 2L- ——> Cats) —2.s4 K‘laql + c. --—) His] 4.934 Li'mq) I c —* ].-i{s} --3.E.I4[l Basic snlulinn (Mg: * HyD-[I] I 2x: —> 03:2} i 20H [ml] H.246 {)[Tl {as}? 4- 11.30“} + 21: —& (Tl ('an + 2 ()ll [an +0390 {M33 + 2 H3011) —. 4 c —> 4 LIH'taq': +IJ.-'|I.]] EHIOU) ! 2c —* Hgtg} | EOH'laq] 1.1.328 8 ...
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