105as07_e3_key

105as07_e3_key - Chem 105a Exam 3 Last First Middle Initial...

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Unformatted text preview: Chem 105a Exam 3 Last First Middle Initial Tuesday, March 27, 2007 Last 4 digits Student ID# Professor Stephens Lab TA’s Name Lab Day & Time: Major Questions Grader 1 12 10 lmal oxi CWQONM-F-WN 20 — 4 _ — .. KC y t0 P O S t INSTRUCTIONS 1. You must show your work to receive credit. 2. If necessary, please continue your solutions on the back of the preceding page (facing you). 3. YOU MUST Use non-erasable ink. 4. There are 11 problems on fl pages. Please count them before you begin. l. (8 pts) The red color of fireworks is due to salts of strontium. The wavelength of the emitted light is 6500A (=650 run). a) Calculate the frequency of the light (in Hz). (The velocity oflight is 2.9979 x loam/sec.) 2.9. KY) P 2 .90”? X10 M/s 650 x Io'qm 7’ "/6!me 3" (Hz?) b) Calculate the energy (in J) of a photon of red light. (Planck’s constant is 6.626 x 10'34 J'sec) lair“ W ‘3 —37’ 19 1‘ é-(o2éxzo 313 ‘MIXID g") 2. (6 pts) Give the values of the quantum numbers n and l for the following orbitals: a) 3d [1: g 1: 2 b) 6p n= (a 1: I 0) 4f n: L} 1: 3 3. (5 pts) List the n=4 orbitals (4s, 4p, 4d, and 4t) and n=5 orbitals (5s, 5p, 5d, Si) in order of increasing energy (lowest energy on left): Lls< ‘ip< §s<44<§p<4f3<$4<§€ 4. (12 pts) For the following elements, write the electronic configurations of their lowest energy states in two ways: (i) the full configuration, starting from ls (ii) the compact form, starting from the preceding rare gas (e.g., Li is (i) 1522s‘; (ii) [He]2s‘) a) boron 2 1 t iS 2Q 2p D437 2&2 if)! b) silicon ls" 2&1 2,?“ 2,37— 36,2. [Ne] BS1 392' c) calcium 2 \s 252 2.9" '39. 39" 43?— [mil ‘isz’ d) zinc ls? 232’ 29‘- 231?)?“ 43’ 34'0 [Ail “lsz 1:1 .0 e) antimony \gzzglz‘PL gs?— Bf3L qSZEJIOL’pL 5’s l) tungsten 2 H (57’ 2&1 zp“ 352'th 49.2 3digital.“ “'01” '{pk 652 “IF S'Jq H [Xe] (0524: 91" 5. (10 pts) Write the electronic configurations of the following ions in compact form: a) A13+ [N4] b) 52' (sulfide) [Ail c) Ba2+ [Xe] d) Sn2+ (stannous) l O [Kw/1 ‘lol‘ogsz org ll" Sgt” e) Ce4+ (ceric) [xél 6. (8 pts) Write the formulae of the oxides for the following elements (all are ionic compounds): a) silicon S; O b) titanium c) strontium d) cesium 7. (6 pts) 3) Arrange the following group of atoms in order of increasing size (smallest at left, largest at right): antimony "Br 4 M < gt bromine b) Arrange the following pairs of atoms in order of increasing ionization energy (smallest at left): magnesium strontium S V‘ < fluorine sulfur S < P 8. (20 pts) Write the Lewis structures for the following molecules. If resonance structures exist, write all possible structures. a) CHC13(chloroform, anesthetic) fiui = #4. l + 1(7) : 2-“ ‘. 5:4: .O :U. 2 C. : Ce: 1C1: b) N2H4 (hydrazine, rocket fuel) '4th = 2 (§)_', t, C.) = H H H :N ‘. N 2 H H lé 0) SiO;;_ (silicon dioxide, silica) :1: V5 \l U LI+ 2(a) 00 .0 Ads . I. ll too 0. a. (1) C302 (carbon suboxide) [Note: the two 0 atoms are at opposite ends of this molecule] *VE = 36;)». 2(a): z‘f éngxgzné 6) N20 (nitrous oxide, laughing gas) [Note: the central atom is N.] *ms‘dfl4o=lg f) HCN (hydrogen cyanide, oison , . p ) int: L+H+ (a M) H:c.:::m: g) C10" (hypochlorite ion, bleach) 3!: ug: n+g+t =I% h) C104" (perchlorate ion, explosive) a}; z D 4' L, (b) + \ = 10 9. (4 pts) What are the names of the geometries adopted by the following numbers of electron pairs according to VSEPR theory? a) 2 electron pairs LlNEA/Q b) 3 electron pairs flied/U41. PLANA/L c) 5 electron pairs "7714mm L 2) PYZAMNOA I... d) 6 electron pairs OCT‘A HQDRA L_. 11 10. (12 pts) Dinitrogen tetroxide N204 is formed by the reaction: 2N02 —) N204 in which a N. . ...N bond is formed between two N02 molecules. N204 is responsible for the brown color of LA smog. It is an experimental fact that all N. . ..0 bonds are equal in it. a) Write the Lewis structure for N204 If resonance structures exist, write all possible :sfrouczures . 5: *ve = Z(£‘)+"I(‘)‘ 3 Y :O:N:wtgt <---> 0::M:M::b: :& ‘. m: b) Draw the structure(s) for N204, replacing each shared (bonding) electron pair by one line. 0 O H I o——N—-t‘\lI—-o 4—7 ozN—t'flzo O O c) Calculate the formal charges on each atom and include them on the structure(s) obtained in part (b) above. 6 O 74 0 Q G) H GD Q )5 \ <7! O—N—N—O é—‘> OzM—-M'—‘=o ('3 n G) l o as 06 d) What is the geometry of the electron pairs around each N atom? EMA N Summer; 2% 3 {prearroe ?AlQL ’TZMDWAL. 31AM AK e) What is the geometry of the atoms around each N atom? TKHOGMAL MAQ 1" 1 1. (9 pts) Consider the following reaction: H2 + 02 —‘) H202 for which AH = —153 kJ. Using the bond energies calculate the 0 ~ 0 bond energy in H202. .. .. .0... 1.12:4 + 0:10 4» H:o.o:l+ ‘0 .O Alla“: ZRE (ReoKm) — Z7132 -lS'Z> K3: <H-l-L)+(o=o)—' 2(o-H)—- (0-0) ——\§3K—X 3 HZZkT—l-HWJ’ZUbVU)‘ (045) NE» K3 ‘-’ (0-0) 13 ...
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105as07_e3_key - Chem 105a Exam 3 Last First Middle Initial...

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