chem1B-Spring_2009-mt3-Saykally_Lester-soln

chem1B-Spring_2009-mt3-Saykally_Lester-soln - /L—...

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Unformatted text preview: /L—§ Chemistry 1B, Exam III April 22, 2009 . Professor W.A. Lester, Jr Possesnestr‘ (10) (10) (10) (20) (10) (20) (10) (10) Name K (g \[ TA TOTAL (100) TOTAL EXAM SCQRE ( ) Rules: - Work all problems to 3 significant figures 0 No lecture notes or books permitted - No word processing calculators - Time: 50 minutes 0 Show all work to get partial credit 1. (10 points) A neon discharge, in addition to its many red photons, also emits photons of wavelength 73.6 nm. When these photons shine on a certain metal-oxide surface, photoelectrons of kinetic energy 10.1 eV are emitted. What is the work function in eV of the surface? Em=w=LEM GP 9... KE = \bfil eu »\0.\¢\/ a (3.9m ¢\/ 2. (10 points) The spectrum of atomic hydrogen contains many lines, which appear in groups with such names as the Balmer series and Lyman series. The Humphreys series is one such group, and all of its transitions terminate at the n = 6 level. What is the energy in eV of a photon that results from the longest wavelength transition in this series? \cmgaarle )\ "’3 éwflilflzfi’ Q E Hg} ,7 V\= (a WVU—SY-EW AE : Ell/{2'3— P Enzé .L .1. f; .— \ A? q, '— 9, . L avasto 3) (3r 5) (\boLKlD'Hj 0.\OO ed ll Page 2 3. (10 points) Arrange the following elements in order of increasing ionization energy: Sr, Cs, C, N, O. C$;SF,C,O/N 4. (20 points) The concept of a double bond between carbon atoms, represented by C=C, has a length near 1.34 A. The motion of an electron in such a bond can be treated crudely as motion in ’a one-dimensional box. (a) (6 points) Calculate the energy of an electron in each of its three lowest allowed states if it is confined to move in a one-dimensional box of length 1.34 A. - w E“ _ Ema , L”— M34 M04" w~~ ‘ Q 2 E\ a U)“ (6.6% M044 39) M... 2. = Became-“*3 Luceu‘ A “gl «LO 5 1 3014001er b3) “ammo m E): 42. >l£4fitcfprj Lester ad) 3,»— OH; = sound”? UM eV) (b) (6 points) Sketch the wave functions and the probabilities for finding the electron in the box for each of the three states. Label clearly. \NONQ gum/hm Page 3 \ . (c) (8 points) Calculate the wavelength of light necessary to excite the electron from its ground state to the first excited state. , «Pr AE: EVE. _,. (anxmog— memo : Loox \0 3’ 3119, AE 7\ 4 ,9, - Ashe : W Z manoewx v «H 43E Loo x l0 {HR WM) 5. (10 points) Give the number of Coulomb potential energy terms in H, H2, and Hf“, respectively. H Hi /@ ® :13; firms l E; 3 6. (20 points) For each of the following write down the lowest energy electron configurations based on the H+ molecular orbitals and indicate the bonding expected for each. Show whether the electrons are 2 paired or unpaired. _ , it ( “‘53 \ \ T a 7/. F(\ k/'—‘—" A 3 LS \. / 6 04K Q Mxl‘ecl \ ‘ ! /. / 0—56 Page 4 W 2»; W / my 30 = 7 ~ o :34 \ \i‘fiia 0‘“ 9' W‘md l$ \ ,r \s \ . T& "r 0.ng 2.. + (c)Hez i B0 : ELL f €31 , oék Z r g “ ‘x W f \ /r l , '— \$ k f 5 \ WMN‘QCK 8 M ’ Oats L%\s)z CORE) \ , (d) If two H-atoms come together and they both have electrons with ms = + 1 / 2, they do not form a chemical bond. Explain this using molecular orbitals. a.” 13-4” is 4...... l6 12 4-4 I \ \ ocmw 01$ memsj 0w“ 073‘ LOW“ ‘D‘WLW‘N O9 Ghowvx ’\\/\ 3:“ WQW ‘ $3K0;L}\£:O p—vao‘omci Page 5 7. ( 1 0 points) Explain the observations that the bond length in N: is 0.02 A greater than in N2 , while the bond length in NO+ is 0.09 A less than in NO. E ,——-q;;\ ”I “5 ‘,--~ , .LRWLBNAW ( l \ ebuwd 1‘: N” ”fiv\\i£’k_i I’U."-* ”‘e M, 9W, 3? \ MW 6511 ’ 2? ‘= i ,9 gyro/my Walk \J/T In. ,’ ' \fifln" \ Tut? ‘ 4 ‘ .. Him)“ (03...? “W (“353% so”. v 50.. .r @013 i go; ‘ -N€'a\\:v‘glw ”int “‘ K “”3““ @ «mgfi L619)” 3 0 = 5 B9 Not 78pm 2. \ , ‘ @ [$954 UR?) (“£93 3‘0 " 23:7 - No a \m 8. (10 points) The following are valence orbital occupation diagrams for the sulfur atom. Decide which of them is the ground configuration, and whether the others are excited states or impossible. 3s 3p 43 a. ll _ L .1 ll —> emfied CAME b. ll. ll. L _L L. ——7 gmum 9mm c 1i it L L .. ’7 1on96512 d. ii- 3 il— —- —— —=z animal e. jl L L L L ‘7 Q‘Ad‘mcl Page 6 ...
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