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practice final- solutions

practice final- solutions - First Letter of last name Chem...

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Unformatted text preview: First Letter of last name Chem 1B Final Exam (exam B), Winter 2005 Name; : ilxlzdgfl 5 Perm° p/VC 5T4 gag / 1 This exam should contain 10 pages (this cover sheet, 7 pages of exam, one sheet of information and a periodic table). Please count to make sure your exam is complete with no blank pages. You have three hours to complete the exam. ‘Show all work and box your final answer to receive maximum possible credit. The exam is out of a total of 200 points. Good luck! Exam 2 p. 1 Chem. 1B 2005 1) (20 pts.) An ice cube weighing 30g at a temperature of -20°C is placed in 350 g of room temperature(25°C) water. The system equilibrates to liquid water at some temperature. Calculate this temperature, assuming no heat loss to the environment. (Assume the enthalpy of fusion for ice is 6.0 kJ/mol and the molar heat capacities of ice and water are 38 J K'1 mol'1 and 75 J K'1 mol'1 respectively. _ a, _ 50‘: ([40 X #2! 3‘ /@,._w/ quj/éoklé'; : [9410/6", 7M4. : (Confklaéwa/ LCzBisxh 4/_E,xcooo +(/.(;X3’§)(/:£'}73) :@93’~7()/?‘H7§ " Hrs 5/4 suqu/J U A °< T%:433.70/< : 5.? 2) (15 pts.) Give brief explanations to receive full credit. a) (5 pts.) Place the elements Se, Br, Ar in order of increasing atomic radius. ‘ Sig—c ("If/“<54 04S 3’0 j/) 61/) Se o/Wsa Gq/ [til/L 0’“ Mmr Hz. b) (5 pts.) Place the elements F,O,S in order of increasing ionization energy. 3 0 F I.£- I’M/cc.” Crs go 0/) 44V! “74,40" Pf’I‘G/(‘c 141%? c) (5 pts.) Place the ions F', Cl', Br", F+ in order of increasing size. -F _. Fr) [/_/-/§/‘ 6) E/ Sci-MI( [lit/III / 2‘27? ('7ff1'q51 Q5 o/axuu. Pfr}ov(.'( Asa Q) PM“ 5.9% MW; 065/ W“? ’{wW—l 2 6 — (COMPEL; 2 (yaséqfi Exam 2 p. 2 Chem. 1B 2005 3) (30 pts.) In the reaction: 3A(g) + B(g) 9 2C(g) + 4D(g) The following experimental data were obtained at 100°C. Exnerimentil Experimentiz [A]0=1.01 x mm [A]0=1.01 x mm Iimeisl mum ['4 [/43 Iimejsl 1AM: L M] 0 1.01 x 10—2 « 4-00 ) _ ,1 0 1.01 x 10-2 460 )-. at 120 8.46 x 10-3 «a? b ' 120 5.99 x 10-3 ~51 I1: 51 240 7.15 x 10-3 -mqg-J? 240 3.55 x 10-3 :5. w '- 360 6.02 x 10-3 4;” ()4?— 360 2.11 x 10-3 —o./e a ,5.) For the following questions, assume that Rat = —M and that only A and B dt appear in the rate law. a) (10 pts.) Determine the reaction order with respect to [A]. (Hint: Note that [B]O >>[A]0, so that [B] is approximately constant in each experiment. Show your work for credit!!) raw/(41“ k' 1:» mfg/7L" w 4a: mg) $I7CK 1.. (0’15 7f- L1 1%] (/5 7L ‘W/flnz /\7.e b) (10 pts.) Determine the reac lon'or er w1th respect to [B]. ’ 2—13/4f/fj:‘/7' : / ”I..([3j 7 [Zap] AF I—fos .00495 ~/ I kfrxfl 2 —A/-4[:]_ $31- 60/41 / 105 00433 ){byjfltb “‘37 3 - c) (10 pts. ) Write down the ate? wand determine the value of t e F‘tex‘fi/ constant. f0: [6 : é [7.71%] Exam 2 p. 3 Chem. 1B 2005 4) (50 points total) a) (12 pts.) Give the electronic configuration for the following atoms and also specify the number of unpaired electrons. (Shorthand notation or full notation are both OK.) Am _ E. . E. . 1 _ i) v m] 4.1 sf 3 ii) c1 [M] 553 $03” / iii) Cu [/rqulgy/lo / b) (6 pts.) Balance the following oxidation—reduction reaction, which occurs in acidic solution: MnO4'(aq) + Fe2+(aq) —) Fe3+(aq) + Mn2+(aq). 54/“ +7; HMJ 7/4.” 44/50 (ficm “"7 F: W) j/f 3-,“ng .Mflo ., J7 ”“4576”ng c) (6 pts.) Write the balanced equation that corresponds to the heat of formation, AH}; of butanol, C4H90H(l). WWW *3/11. (fl) “fl/Z0 0(3) ”>( ¢70////// d) (6 pts.) Give the complete electron configuration for Kr. (Do not use shorthand notation! Write out the entire configuration and be careful. There will be no partial credit here.) /5‘l saw/35“ éoé Leggy/”4f Exam 2 p. 4 Chem. 1B 2005 e) (6 pts.) The following reaction has E°=O.78V. Calculate AG0 for the reaction. Cu2+(aq) + Fe(s) —) Cu(s) + Fe2+(aq) AGO: 4:6” pl F: %/M%w/r : ‘9‘ W; “8770. 7? f) (8 pts.) True/False. Circle the correct response. i) The following series of ions is isoelectronic: Na+,K+,Rb+,Cs+. ii) HF is an example of a molecule with a polar covalent bond. iii)Third row elements are always expected to obey the octet rule. iv)In a galvanic cell, electrons flow from cathode to anode. v) In an electrolytic cell, electrons flow from cathode to anode. vi) CO2 has a non—zero dipole moment. vii) CN' has a non—zero dipole moment. viii) A 3p H orbital has additional nodes relative to 2p orbitals. g) (6 pts.) How many electrons in an atom can have the following designations? 1) 5f “15f ______ ii) Spy ___2 _______ iii) ZS 1 iv) 2d 0 v) 4d 1 xy ——————————— vi) n=4 6“) (D 6) [email protected]@@.® Exam 2 p. 5 Chem. 1B 2005 5) (15 pts.) a) (5 pts.) Draw a Lewis dot structure for the molecule CS2 that satisfies the octet rule and insures that every atom has formal charge of zero. M “S :C :5 b) (5 pts.) Draw a Lewis dot structure for CS2 that satisfies the octet rule, but does not make the formal charges on each atom equal zero. Make it clear what the formal charges are. ’ .SWCES .' ‘00 3 15:4 (90 @w 0') Ga (* (a) c) (5 pts.) Draw an acceptable Lewis structure for the ion 13' that adheres to all relevant conventions discussed in class. 292— [ich—LJ 6) (10 pts.) The skeleton for the molecule “crotonaldehyde” is shown below. Each line indicates a single bond. Draw in double bonds, triple bonds and lone pairs as necessary to create a valid Lewis structure. (If you are unable to do this, give the number of electrons you need to place in double bonds and lone pairs for some partial credit.) ' H i H I7L H I l I I - H— C C35, C: / L} Exam 2 p. 6 Chem. 1B 2005 7) (16 pts.) The rate law for a reaction is found to be Rate = k[A]2[B]. Of the following three mechanisms, which ones are consistent with this rate law. Show all work to receive credit. - c I II] a C A+B 1’] E(fast) A+ a A+Ak—>E(slow) ‘77 B «L E (fast) E+Bk—)C+D(slow) E+Ak—>C+D(slow) E+Bk—>C+C(fast) J .L [E] ZWJKé / - M 9‘ E r0, c -— 4‘1 fqlcuég: 12:6:1 {lid—4 I'mW‘Lfl’) 7 1/ @175] 3 [CI/HM] age/(1%, [flaw] ,34. I 533%,[43651 ‘/«’$’ rfileaé 1k lgfimfl {([AJZ’Q]; 0-1/7 Mng/l (5‘41 & Mal (‘5 {-0~4§(‘§ )Zfflf. 8) (15W pts. ) Use the following informamaté t e bond energy of the Nitrogen- Nitrogen bond in the N2 molecule. AH; for NH3 = —46.0 kJ/mol N—H bond energy = 391 kJ/mol H—H bond energy = 432 kJ/mol {4/3) 12M) “WW/31 —% b’w/ Exam 2 p. 7 Chem. 1B 2005 9) (15 pts.) The energy levels for an electron in a box are given by 2 2 n 11 En = 2 8mL ' It is known that photons of wavelength 8080 nm are capable of exciting the electron from the n=2 to n=3 energy level. What is the length of the box? F. .:”’7 5—54} L&:24“J , £5] 2 g “'14; Y CM CM / :[ 5’}; (20.19% ”’5 28080wa. c, qu/x Ex}xroYH/5 )v ’Zbcpuo'3/é 51M 10) (14 pts. ) Consider the generic potentia)l energy diagram below. c (i ) (fl ) Each letter in the above diagram corresponds to one of these terms: Reaction coordinate Products Reactants Potential Energy Ea Enet AE Transition State Arrhenius Energy X Catalyst Work Function Write the correct term next to the letter it corresponds to on the diagram. a) __E€_q_c_‘(:_f> __________ e) _.___Z'<:&\ ___________ b) __P£egx(a_c_{2 __________ f) ___(3_m£p____Co_q/zfihfiy/C c) _72142££&J._SAKZ____ g)__-__&d14451__2_1rJ7 d) ___,A_(Z ____________ ...
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