14a01fa_revised - CHEM 14A Instructor Dr Laurence Lavelle...

Info icon This preview shows pages 1–16. Sign up to view the full content.

View Full Document Right Arrow Icon
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 4
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 6
Image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 8
Image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 10
Image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 12
Image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 14
Image of page 15

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 16
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: CHEM 14A Instructor: Dr. Laurence Lavelle FALL 2001 FINAL EXAM (Total number of pages = 16) (Total points = 100) (Total time = 3 hours) ”Carefully remove the first page which is your Periodic Table.** YOUR TA'S NAME ...................................... WRITE IN PEN (Show all your work on this paper.) Constants and Formulas Planck constant, n = 6.626 x 10‘34 J - s Avogadro constant, NA = 6.022 x 1023 mol'1 Rydberg constant, R = 3.29 x 1015 Hz Gas constant, R = 8.314 J.K".mol'1 Mass of electron, me = 9.11 x 10’31 kg Mass of neutron, mn = 1.67 x 10‘27 kg Speed of light, c = 3.0 x 108 m.s‘1 0°C=273.15 K 1L=1dm3 1atm = 101.325 kPa n=3.14 h2n2 E=hv E=pc En=8—mE2 p=mv h? h En: ' .62- A=E E—1 v2 —A A Ax>L —2m C— v px _4n — -v§2- Solution toAX2+BX+C=O is X: B+l 2A 4AC Do'not write on this page. QUESTION SCORE 01) A. What is the shape of SE, and explain why it is polar? (4pt) Ans) SEESAW (2pt) It is polar because the dipole moments of the equatorial bonds do not cancel. (2pt) :l : /-f-‘ 8 s l \.'E°= .F.‘ AX4E B. How many sigma and how many pi bonds are present in the anion: (2pt) HaC—CH=CH—CHz-—O ' Ans) 11 sigma (1pt) 1 pi (1 pt) C. Knowing that carbon has a valence of four in nearly all its compounds and can form chains and rings of C atoms. Draw a possible chain structure for CaH4. Label the bond angles and label the hybridization of each carbon atom. (6pt) Ans) H If H 3,2,2 A — £. /2 / 130' 1C‘\ H I/oLH or :f H __\I lw!’ H— =_ C_"‘ C H i ’5" IR?” IF H 2 pt for a stucture 2 pt for bond angles 2 pts for C hybridization D. Draw the correlation diagram for two 0 atoms forming 02. Label the atomic and molecular orbitals and show the valence e- in the atomic and molecular orbitals. (4pt) Ans) 02 Molecular Orbitals Atomic Orbitals Atomic Orbitals —. LUMO G 2Pz (I. i HOMO TE 2Px 7t 2Py 4i “i 1 1V 1 1 2p 29 d” .4! fl 2Px 4—” 1T 2Py O'2Pz ENERGY fl 4V 6. 40 23 41 2s 2s 0 0 it 025 02 1pt for correctly labeled orbitals 1pt for correct AO e- configuration 1pt for correct MO e- configuration 1pt for correct energy level representation Calculate the bond order for 02. Ans) BOND ORDER = 1/2 (8 - 4) = 2 In your diagram above, label the HOMO and LUMO orbitals. Write out the atomic e- configuration for atomic oxygen. Ans) O ATOMIC e- CONFIGURATION IS [He]2s22p22p‘2p1 Write out the valence e- configuration for molecular oxygen. Ans) O2 VALENCE e- CONFIGURATION IS (0292(0'23)2(02pz)2(n2.=)4(n’2p)2 (1 pt) (1 pt) (191) (1 pt) 02) A. What' Is the velocity of a neutrorZ that has a wavelength of 100pm ? (2pt) 214;» V . 1/ —— 5-57/{X/0’35L3‘J (711— ) / {HBr/51% {/oox/O"IZ>M ~ ? ‘I K ‘8 1a.: 3 (251? “QM :- 3 77m 5 X/o (M) B. What is the electron configuration for Cr(l||) ? (1 pt) Answer: [Ar]3d3 C. Which of the following has the largest bond enthalpy? (1 pt) F2 CO 02 H2 HI HBr Ans) CEO Only molecule with a triple bond. D. As the order of a bond increases, its bond energy and its bond length (1 pt) Answer. 0) increases, decreases 27:1 EM E. If four orbitals on one atom overlap four orbitals on a second atom, how many molecular orbitals will form? (1 pt) F. Which of the following statements is FALSE ? (circle your answer) (1pt) a) Atoms or molecules with an even number of electrons are diamagnetic. b) Atoms or molecules with an odd number of electrons are paramagnetic. c) Paramagnetism cannot be deduced from the Lewis structure of a molecule alone. d) Paramagnetic molecules are attracted toward a magnetic field. e) Némolecules are diamagnetic. Answer: a) Atoms or molecules with an even number of electrons are diamagnetic. G. True or false: Transition metals show great similarities both within each period and within each vertical group. (1 pt) Answer: True H. Write two coordination isomers for [Fe(NH3)5SO4]Br (2pt) [Fe(NH3)5Br]SO4 {/M) [Fe(NH3)4BrSO4]NH3 071') l. Which complex ion shape is NOT capable of showing cis-trans isomerism? (1 pt) Answer: tetrahedral J. Define stereoisomerism. (1 pt) Answer: Stereoisomers have the same bonds but different spatial arrangement of their atoms. K. Name two properties that enantiomers have? (2pt) They rotate plane-polarized light in opposite directions. (7‘79 Their structures are not superimposable. Q7”? L. Draw the trans isomer of [Co(en)2C|2]+. (1 pt) ls its mirror image superimposable? (1 pt) YES Is it optically active? (1 pt) NO Is it chiral? (1P0 NO What is the oxidation state of Ni in Ni(CO)4 ? (1pt) What is the name of the complex [Mn(NH3)5I]Br2 ? (1 pt) pentaammineiodomanganese(III) bromide 03) The photosynthesis reaction is 6 002(9) + 6 H20(|) = CBH1206(aq) + 6 02(9) and AH° = 2802 kJ. Assuming a dilute reaction, briefly state what effect the following changes will have on the equilibrium composition. The partial pressure of 02 is increased. 1pt) Mfl/floéfl' gf WW< ‘The system is compressed. (1pt) WW The amount of 002 is increased. (1 pt) The temperature is increased. (1 pt) 443117 WW Some of the CeH1206 is removed. (1 pt) Water is added. (1 pt) The partial pressure of C02 is decreased. (1 pt) fife/W 10 lf Kc = 61.0 for the reaction N2(g) + H2(g) = NH3(g) Write the general expression/formula for KC. (2pt) N2(g) + 3H2(g) = 2NH3(g) 01f ) [NH 12 KC =[N21i1342] 0712‘) Under the same conditions what is the value for Kc of the reverse reaction ? (1 pt) 1/Kc =1/61.0 = 0.016 Write the general expression/formula for Kc. (1 pt) Ca(OH)2(s) == Ca2+(aq) + 2 OH'(aq) Kc = [032+] [0H'12 Write the general expression/formula for Kp. (1 pt) CaCOs(s) == CaO(s) + C02(g) KP = P002 11 E. When solid NH4HS and 0.200 mol NH3(g) were placed into a 2.0 L vessel at 24°C, the equilibrium NH4HS(s) = NH3(g) + H28(g), for which Kc = 1.6 x 10", was reached. What are the equilibrium concentrations of NH3 and H28 ? [1‘ (8pt) . . . 2 if (Show all your work In obtaining your answers.) &. /00 f/(x /o z g f 4/ W W " , 04’“) KC = Walks]: (0‘ W my: (1200‘ Md ”6 +0/ooflo.—/;X/;4‘_,o (W) m... “Mm/(Mo) «MW-W“ : WW ”W 2 071/ I: ~"O/DOj; O./03/5’ : a.00l5~5‘m/ ”alolé Q, ’/ .L (/0473 {ALP} —— 5/00 +(2x/f] = 0”sz é I-o x/J' Q/fltC H25] : fix/03 (25,1? “77%) 12 Q4) A. Cacodylate acid, (CH3)2AsOOH, is used as a cotton defoliant. A 0.0110 M cacodylate acid solution is 0.77% deprotonated in water. (Show all your work in obtaining your answ% 23% ls cacodylate acid a strong or weak acid ? 2pt) ( M W 0.7%,; W What is the pH of the solution ? (5pt) (at; Z Aw” % 6532450; + Hjo" fig”; W (6,95, “float/:- 0.01/0a<§0000/7;) - o 3 0.0/0fllwré.z/ 0L3 07L} :W/éx]: fi.069~7—X 0.0%? M =2 3.!X/o‘fM.Z/ (2)117 Why should cacodylate acid not be used as an cotton defoliant ? (2pt) Contains arsenic which is highly toxic. MW 13 B. Derive the Henderson Hasselbalch equation for the following general expression of a buffer solution. (6pt) HA(aq) + H20(l) = A'(aq) + H30+(aq) KPW {/7417 [AH] [Hm = KA {2—511 071/ -LOG [H3O+] = —LOG KA -LOG [fit-'11 0717f) pH=pKA+LOGJ[:fi—;_|]]' QM) SINCE IT IS A WEAK ACID __ IA- IINITIAL SALT pH — pKA + LOG [AHllNITIAL AClD 2741‘ C. What are the optimum buffering conditions for a buffer solution ? (2pt) [ACID] = [CONJUGATE BASE] Ol' PH = PKA 14 05) A. A 15.0 ml sample of 0.15 M NH3(aq) is titrated with 0.10 M HCI(aq). (Show all your work in obtaining your answers.) If Kb for NH3 is 1.8 x 10'5 what is the initial pH of the O. 15 M NH3(aq) ? (5P0 ¢% /flzo 7“”63 361)? ”6%(47) +0//(47)(/%1) o If“ X X «Lwr m /.5X/0 — 0-/J’-X d45' C7919] 2- / (5 7% 3W (/1!) lb of/ 3 2.30 (’71,) an What volume 0f 0 10 M HCI(aq) is required to reach the stoichiometric point? (5pt) W M; -: M: ll/oe M54 MIX 2 (a 0/{0 L) [a xrwfz, ) ~— Z-ZR/amé 15 C. Calculate the pH at the stoichiometric point. (8pt) fife/EW‘flW/s/zoflw/fl Hf 7L g ##7‘ 7L/zc~ ($7) ”627) , {‘61/ M] MZVoWé f WM (Wt) ””44 +61) " ”ate/‘7 A377] 35‘” 071‘) mm :: /f fear: f? (M / .1? i : ZZKX/pxwéc gnaw/L, (M/ 94%] (9037.3’4 0 46 I : .51"..- /o/¢ ’_ ( / [/M) 4” A74 _ /. iX/a" I {1 X & ../o & 4K {/Wt/ KAT/5' éX/a 2: 0.0(0-'X H 00(0 D. Name an indicator suitable for this titration. (2pt) METHYL RED pKin = 5.0 16 ...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern