exam_answers_ex_2 - - 3‘1 CHEMISTRY 152A HOUR EXAM II...

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Unformatted text preview: - 3‘1 CHEMISTRY 152A HOUR EXAM II (Version B) Fall '04 Tuesday, November‘23, 2004 Name: TA Section: 0 . Student Number: , TA Name: Score (page) 1 , I 2 _ GOOD LUCK! 3 _ r . 4 5 I. CONCEPTUAL AND SHORT ANSWER: (~ 4 pts each, total 72 pts) 07:12)‘ (9 (3) (1/) 4 (a). (‘0 1. Give the sign of the cell voltage 8 and AG for both a galvanic Cell and for an ' electrolytic cell. Which is spontaneous? ' 2. (T® gq/uewzt: 5’ >0 ) A G’C 3) 3/mézeou; bag? e/ec2¢9/;7('c: g<_o) A 6>o , Ovafi’SpmiébPOOS’ In a galvanic cell, the electron flow is from the cathode to the anode, while in an electrolytic cell, the flow is from the anode to the cathode. ’ 3. In an electrolytic cell, oxidation occurs at the (cathode, Qnode ), While reduction occurs at the anode). ‘In a galvanic cell, oxidation occurs at the@ cathode), while reuction occurs at the anode). (Circle correct terms) . 4. Why do “45” type orbitals fill before “3d” type orbitals? l I P €7,qu VS ' p/ec A 44; Sum 4r fro/6.4% a flPnMé’W‘V) F/(‘e/{en‘ _ 5. Ionization energy decreases) across a period, and (increases, ecreases ) down a period. Atomic (covalent) radii (increase, decirease) across a period, | decrease) down a period. (Circle correct terms) a 0/991“ 24 0700/ch flew Ara-Av ’50,! M K”) (w m V 6. Give an expression for the electron affinity (EA) of a gaseous atom X(g) Why does EA always have a negative value? - 4// 4’43'5'II'0M) {A 91/96,»? 35/35- 54 <6 57hr? #12: flrarrsr 1's (Xafl‘iml?) . . . 7" . 1"“"97 c/PC‘MIQ. 7. lee the electron configuratIOn of the followmg atoms or lons: - . Ge+ 32"”) [Cr (We? 322522/043513/cl/3230/491 piszzgzZ/gijzs/C#Jplgo,f ' '1' 76"] (kg/0%“ 9” M’r] I/s’ads’ 8. Why are polar coordinates (r, 6 , (1)) preferred to cartesian (x,y,z) in the quantum mechanical solution to the wave equation for the hydrogen atom? ‘ ~ I ire, [pa/q y Coordyiw q//ck/5 s‘gacrcr/{aa 9/ #9 wall") :‘a :‘Pflq‘ra [/r 1'7; md/b/ a no) @173 a/qr even»: 9. For the particle—in—a box, why is n=0 not an allowed solution? What happens to the pattern of allowed" energy levels as the length of the box (L) 'is decreased? I» :6 an Pg”: £0») :0, flqVJZ‘r/f 47’N5/, 5", ’"f “"r‘” ”' /' a / 93/5“ [43“) 6‘? mm A UM “lie-04”) éwr‘PI/éflvé fl’l‘w‘l' ’6’. ' WW “‘7”, ’6 low/54 W} /'~ fl! éax (‘w’c/ c Active» Card/7‘4“). ’49 Z c’s't‘lcreseo’ . {merge /¢-W/5‘ /;, (meg-5‘9, 97)”? 44' _ ‘10. There IS an exact quantum mechanlcal solutron to the wave equation for the H atom, but not for any other polyelectronic atom or ion. Why? ('9 Ire/942 e/ec/‘Voh - P/ec n S/‘ak , 11. The energy levels of the hydrogen atom depend on@l, m1), while the energy ‘ levels of all other atoms depend on @ m1 (Indicate the correct quantum numbers). 12. Name the two physical phenomena, the explanations of ,which were most » important in the overthrow of classical physics at the beginning of the 19th century, leading to quantum physics. y. Led? radio/Zia ,. pkg, (4/?ch efic/ ‘ V 51, 3. V) 13. In the very early universe (about 400,000 years after the Big Bang) hydrogen ions (H+) everywhere recombined with electrons (e' ) to form neutral hydrogen atoms in the ground state (n=1). What is the energy (in Joules) of this transition? a jaw/9914b“ 97) ~39 o;/ : 22/}? X/& ‘ 3) 14. What is the main reason why all members of the same group in the periodic table (nsX py) have similar chemical properties? 7-4 me ya; /(h(‘f Mar/Cam can 61"? (ll) 15. Complete and balance the reaction of the alkalai metal K with water: 2K(s) + 2H20(1) —> [/2 (9) + 2/42” + 20%;?) (4/) 16. Which has the larger second ionization energy -Li or Be, and why? ’ r ". ls7zy/ Z". 4 I57— oy my)qu yé remuc Cam I P ’96 jam 4/ * flak - z 2 J / ‘ I Be ‘ [5 25 gf ,5 125- , 2; w/Pnrc P/Cc/‘Gh ,6) 17. What is the total number of orbitals available for n=4? Total number of possible electrons which can be accommodated in these orbitals? . mm 0,1, '4/r arid/344' (m=£/) :mz;/6‘ «(50 411-50 4/: / 90’0"” (%I/’%/) = [327 of” = I 43, 56/:7 K/p 3 /= 2 mp:0,;‘/I£1 yd ' r /=- 3 m, : a, :11, :7, t; 46/ 9 ' (40'!) I my {3' ( 3) 18. (T@ The best reducing agents have the most positive standard reduction potentials, hence are most easily oxidized. II. QUANTITATIVE: Do any two (2) of the following (14 pts each, total 28 pts) I (,y) 1. The hydrogen fuel cell: 2 H2 (g) + 02 (g) ——> 2 H20 (1), t has an equilibrium constant K(eq) = 1.47 x10+75 at standard conditions (T =298 K). (a) Calculate the standard cell voltage 80 and also AGO (b) Predict the signs of AH0 and A80. (0) How does the maximum work (wmax) obtainable from this cell change as the temperature is decreased? .o i I 9; ' (4) fro/F “£2” 419/; (1”?) '.‘ aegis/@(M’? “0+ )‘ A 6": ~77}E;,:/’ :: :E- 977/2; (A) AgogA//°_7A§‘ . Ag< 0/ AS<O {7qsrr-5/I'9a,/jl 5c ' 4/71 Inn's/1e <0 (C) 10,", : (16 = 4/,“ ~7Z}S ¢5 7 decms‘efl % A/7’ Jon/*9}: .awr (~gc)/ .sa ((6 x‘nrmféz (0,,” hart/€659: (I'd) ‘ 2. An excited hydrogen atom H* emits a red photon of wavelength A = 656.7 nm (nanometers) as the electron falls to a final state 11f: 2. What is the initial state ni' of this transition, and the energy of the photon ( in Joules)? - / ' Ag,— -7./)3)’/a 57/qu = A74 7 AC: I -57 A 9 . 4;: (6.674X/o 75 /299?/WM L. Cfl-P'X/a‘zn A5 4789-651”, 7957/9» K935" Mr}; 93 (“"179 B'OZIX/a T 7 /?fi 7’ 47,?) ,1. a,” : 4,17. : —-Z—— : 7.00 a. I/// 4”” :3 Consider the reaction producing the disinfectant chlorine dioxide: 2c102~ + (:12 —> 20102 + 2c1’ Using the standard reduction potentials of C102 and C12 given below , calculate the standard cell-voltage 80 , the Gibbs free energy change AG0 , and the equilibrium constant K (eq) at std conditions (298 K). €12 + 2e‘ -> 2c1 e°=+1.36V (2102 + e' é C102" 80 = +0954 V arc/f : 65:4 -€c,:n¢a/é : /‘36_ fl'?g7/ :@ a_ To .7 34, 851$ ' " 5%; 4/5"”3'5 (Z// a) 456°: #7293” ' 5;,”- 0.05”?/ 59 A47 47 r /o 1/ , ‘ 7 "'7 {ii/£443 o.¢// _ 33} 0459/ 0 05‘9/ ’ ' ...
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This test prep was uploaded on 04/07/2008 for the course CHEM 152 taught by Professor Chiu during the Spring '08 term at University of Washington.

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exam_answers_ex_2 - - 3‘1 CHEMISTRY 152A HOUR EXAM II...

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