177Exam2KeyF07

177Exam2KeyF07 - PROF. THOMAS J. GREENBOWE DR. KATHY BURKE...

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Unformatted text preview: PROF. THOMAS J. GREENBOWE DR. KATHY BURKE HOUR EXAM II OCTOBER 1, 2007 FALL 2007 THIS EXAM CONSISTS OF 20 QUESTIONS ON 6 PAGES fiRADINQ PARTS POINTS SCORE Page 2 21 pts Page 3 15 pts Page 4 32 pts Page 5 32 pts TOTAL 100 pts CHEM 177 NAME an Sb”: 1: E41; RECIT. INSTR. RECIT. SECT. NOTE: THE METHOD YOU USE IN SOLVING QUESTIONS MUST BE CLEARLY SHOWN IF YOU ARE TO RECEIVE FULL CREDIT. QUESTIONS ARE WRITTEN ON BOTH SIDES OF EACH PAGE. THE LAST PAGE CONTAINS USEFUL INFORMATION AND A PERIODIC TABLE. THIS SHOULD BE REMOVED AND USED FOR ADDITIONAL REFERENCE AND SCRATCH PAPER. DO NOT PUT ANSWERS ON THE TEAR AWAY PAGE. Teaching Assistants and Recitation Sections Name Bernie Anding Cynthia Bunders Shantha Daniel Christopher Ebert Tanya Gupta Emily Hull Zainab Khan Brandon Kobilka Rose Kohl Jason Lupoi Nataliya Markina Emily McDanel Megan Mekoli Derrick Morast Sahana Nagappayya Nicholas Nagle Gerald Pollock Nathan Schulz Justin Valenstein ‘ Anthony Young ‘ Chad Yuen Sections Time 6, 29 11:00, 3:10 23 8:00 5, 27 10:00, 12:10 13, 17 9:00, 12:10 9,11 2:10, 5:10 28, 35 2:10, 5:10 10 4:10 2, 4 9:00, 10:00 20 2:10 8, 15 2:10, 11:00 16 12:10 12 8:00 24, 25 10:00, 11:00 30, 34 4:10, 9:00 18, 22 1:10, 4:10 32, 33 4:10, 5:10 7, 21 1:10, 3:10 1 8:00 19, 26 1:10, 12:10 3 9:00 14, 31 10:00, 11:00 2 PART I — Multiple Choice. (12 questions at 3 pts each = 36 pts total) 1. Which of the following compounds is a strong electrolyte? @xon Identify the major ions present in an aqueous HNO3 solutiou. a) HN+,O2‘ d H*,N3‘,02‘ b) 0H-,N0; H+,N03‘ c) OH‘, NO a) H20 b) N2 d) czHfio (ethanol) e) CH3COOH (acetic acid) Which one of the following is a redox reaction? a) H*(aq) + OH’(aq) -> H20“) b) 2KBr(aq) + Pb(NO3)2(aq) —* 2KN03(aq) + PbBr2(s) c) CaBr2(aq) + HZSO4(aq) —> CaSO4(s) + 2HBr(aq) 2 Airs) + 3 stoaaq) 4» Ausoaaaq) + 3 Hag) 3) C032'(aQ) + H804_(aCl) _’ HCOa-(aQ) + 3042—(31‘1) What element is reduced in the following chemical reaction? Cu + 2112804 —=- CuSO4 + SC:2 + ZHZO b)H @S d)O Which of the following represents a combustion reaction? 2 was + 702(g) 4’ 4co2(g) + 6H20w) b) LiOH(aq) + HNO3(aq) —> LiN03(aq) + H200?) c) Nag) + 3 Hag) —> 2NH3(g) d) 2Na(s) + 2H20(€) —> 2NaOH(aq) + H2(g) e) 22%) + 3 stouaq) a Ausouaaq) + 3mg) a) Cu e) H20 A compound has an empirical formula C3H2N; the molar mass of the compound is 312.29 g/mole; what is the true formula for the compound? C13H12N6 If solvent particles are represented by (O) and solute particles by (O), which is the more concentrated solution, A or B? a) C3H2N b) C6H4N2 c) C9H6N3 (954» MW WW z ,owmt kw M: Jqu 3 56.15%?” 3 8. A student prepared a stock solution by dissolving 5.00 g of KOH in enough water to make 150 mL of solution. She then took 15.00 mi. of the stock solution and diluted it with enough water to make 65.0 mL of a final solution. What is the concentration of KOH for the final solution? 0.13? M b) 0.178 M c) 5.61 M d) 7.30 M L O 0.0::0Lx. 975‘M“' g i009?! Mel Q m = M}: O. 1 3})ko/ L .0651. ’Z' 9. The mixing of which pair of reactants will result in a precipitation reaction? Cu(N03)2(aq) + Nazcoxaq) c) Nac10.(aq) + (Nansoq) b) KZSO4(aq) + Cu(N03)2(aq) d) NH4Br(aq) + NaI(aq) 10. Write a balanced net ionic equation for the reaction of CdC12(aq) with Na2$(aq). a) CdC12(aq) + NazS(aq) —> CdS(aq) + 2NaCl(aq) b) Cd2+(aq) + 2Cl’(aq) + 2Na+(aq) + SZ'(aq) ——> CdS(s) + 2NaCl(aq) @Cd2+(aq) + Sz‘(aq) —a- CdS(s) e Cd2+(aq) + 2C1'(aq) +2Na+(aq) + Sz‘(aq) —* CdS(s) + 2Na+(aq) The following information and diagrams pertain to problems 1 1 and 12. Assume that an aqueous solution of hydroxide ion, OH‘, represented by unshaded spheres, is allowed to mix with a solution of an acid, HHA, represented by gray spheres. Three possible outcomes are represented by boxes (a)—(c), where the black spheres represent A"', the anion of the acid. For clarity, H20 molecules are not shown. (a) 11. Which outcome corresponds to the reaction: HCN + OH‘ —> H20 + CN‘? a) box (a) b) box (b) c) box (0) Cd) none of the above 12. Which outcome corresponds to the reaction: H2804 + 20H" —> 2H20 + 3042'? a) box (a) b) box (b) ® box (c) (1) none of the above 4 PART II — Problems. Circle the correct answer. Show all work. (3 questions at 8 pts each = 24 pts total) 13. (8 pts) Calcium oxide (molar mass = 56.1) reacts with water in a combination reaction to produce calcium hydroxide (molar mass = 74.12): CaO(s) + H2002) —> Ca(OH)2(s) In a particular experiment, a 5.00 g sample of CaO is reacted with excess water and 6.11 g of Ca(OH)2 is recovered. What is the percent yield in this experiment? a) 1.22% b) 6.61% c) 7.19% 2.4% c) 81.9% S‘. CAI) x lwtol (0.0 lmi CaCO’OLx :FfJZ C‘" H)'L = G. G CQ 0% "_"—_—_—_— x c O l M! l Cato”); W 2' 96.1 C5 Cat) 1 Mel 0‘ (Jure'i'fia/ X- o “MOM-“J” x {00y :- 6‘ y a —- d - = H d o c ’4' 0 fl) 2!; U A ‘6. 2ch H h my.“wa 64-37% 72 ? / 14. (8 pts) What is the concentration of fluoride ion in a solution of 0.150 M GaF3(aq)? a) 0.150M c 0.300M b) 0.0500 M a 0.450 M Airy-wt. a. {-00L 5 Gamma 65 .2 MP"- assume/f“ {Hatfie— M3 Mr": awe/*1 F" AWLJU“ 15. (8 pts) The specific heat of copper is 0.385 J/(g-°C). If 34.2 g of copper, initially at 25 °C, absorbs 4.689 kJ, what will be the final temperature of the copper? a) 25.4 “C b) 27.8 “c c) 356°C 381 “C $3.1Mch ‘ = 34.2 K 03353 T; ~25'.o"C) ‘1562927 3 FTC ( q; s 3“ Hrdc $62123 _ , - _ .-.— 351% ~ "lit—Lap"; " - '33] ’C jar—2; .zarJguc) ” PART III — Problems. Show all work. Answers should include appropriate units and contain the correct number of significant figures. (5 questions at 8 pts each = 40 pts total) 16. (8 pts) A 7.284—gram sample of a compound of selenium and bromine contains 5.841 grams of Br. What is the empirical formula for this compound? )3 [not r- o fiS’thr 0?} II3 93.13% cwa 5-34/3 Br v ~ - v __._"'° F 5 W .018 3 «J h F' S. 9 “M3 fir LCM”? fie “721659: ____.._£ 1561}; i IN” 5 17. (8 pts) Find the volume of 0.110 M HBr necessary to react completely with 1.52 g Al(OH)3 (molar mass = 78.01). _'3__HBr+l_A1(0H)3—> A1313? r- BHCOM) [52:5 RICO“), 7‘ [Ml A‘__C°.__H)J K Mr _— 0-03—er! Hfir was I41 (oh); mt mo»); : :dznulu fetal-v _ A 1% . arr-2L tip/m" 7T — O-OSXINJHIK' xo'llgmofigl'h 18. (8 pts) A 0.230 L aqueous solution of 0.180 M MgCl2 is prepared. What volume (in units of mL) of a 0.200 M aqueous solution of AgNO3 is required to completely precipitate all of the chloride ions as silver chloride? MjCkCat) ‘1' 2A5N03fiazj '—> 145cm); Myth/07>:ij O. ZKQL s! Ha, M Clzx w: Val: Lem! = 0.4142 VO(M(QC4-9N03 nw . 2m} ml/L 19. (8 pts) Consider the reaction: 3 H2(g) + N2(g) —> 2 NH3(g) and the corresponding particulate nature of matter level diagram given below. a) QQ=H2 AA=N2 O&=NH3 Before reaction After reaction b) Which is the limiting reactant? I 20. (8 pts) When 1.50 g of Na(s) is added to 100.00 g of water in a calorimeter open to the atmosphere, the reaction shown below occurs and the temperature of the resulting solution rises from 22.00 °C to 33.10 "C. If the specific heat of the solution is 4.18 J/(g°°C), calculate AH for the reaction, as written. 2 Na(s) + 2H20(£) -> 2NaOH(aq) + H2(g) AH = ? Emt 59L "* 9‘ 55.1“: 0.2351)“ Mayra) lXT(1Lro"cJ= +43%? Cf. fir: Erme‘fiow (.m u... x WM“ marina! OI .. 5 2W?“ H“ flux”? : ":fflfli; : j I W698! k%v( 75L. . . 0657)“) ha ...
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177Exam2KeyF07 - PROF. THOMAS J. GREENBOWE DR. KATHY BURKE...

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