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c123_2008_quiz4_key - Dr Woodward Spring 2008 Chemistry 123...

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Unformatted text preview: Dr. Woodward Spring 2008 Chemistry 123 Quiz 4 Wednesday 11:30 am 20 Minutes Name Lab Inst. Two-Digit Section Number ALL WORK MUST BE SHOWN TO RECEIVE FULL CREDIT 1. Indicate whether each of the following statements is true or false: a. [1 point] All alloys are homogeneous solid solutions. PEA: 2 b. [1 point] Substitutional alloys generally form between two metals with similar radii and bonding preferences. A \ rope—a 2. [1 point each] The absorption spectra for two different complex ions in solution are shown below. Based on these spectra what color would you expect each solution to be? 14 1.4 Compound A Compound B 1.2 \L LQDbOAJS 12 _ crmmcxl-a 1.0 -- 1.0 3 3 g 0.8 g 0.8 *3 ‘5 I: 0.6 -l J: 0-5 0 4 - . O 4 0.2 -'-// 0 2 O D - -- - O 0 400 500 600 700 500 300 400 500 600 1’00 800 900 wavelength (nm) wavelength (nm) Color = Bhu—a Lew \[iuLL‘V’BhJ—i.) 3. [6 points] For the transition metal complexes below complete the following table. Cm Um; {Bra/ox 3 Coordination Number Electron Confi . uration Oxidation State Compound [Pt(NH2CI2)] K2[TICI6] Na4[Mn(CN)e] Q1-W1123O 1 4. Both gold and platimum metals have a cubic close packed structure as shown below. a. [1 point] Based on their positions in the periodic table which metal would you expect to have larger unit cell, gold or platinum? ukfm mou‘wxcx \L?\'—\'o—r‘tos\,~:\ 7% m PU‘TOATL “sou, MM LfiLLlr‘mq Mum. shaky; ‘uA an; 0.32/3 60 flu:— mA‘t wS Aagreosas flaws (pm v mine LAO ©_\_ “5‘“ Mt Qd\qrc)‘Q_/\ Mix CL\\., _._..— b. [2 points] The X—ray powder diffraction patterns for gold and platinum are shown together in the diagram below (one in gray whose peaks are labeled with a 1, and the other in black whose peaks are labeled with a 2). Based on your answer to part (a) which pattern do you think corresponds to gold and with pattern corresponds to platinum? 1X : 7L:£,€$V\_é3 a}; *x¥k. LkYCAr'QL‘\ 0.x? CIA-WAS é T m Em 43% Intensity (arbitrary units} 30 35 40 45 5O 55 BO 65 70 13+ 26 (degrees) Phase 1 = (3: w Phase 2 = c. [1 points] What type of alloy would you expect to form between gold and platinum (substitutional or interstitial)? Sm‘tbfiajflkcuk'hm/la/Q 3 Law m +u.>v3 Amt/L5 Grub SRWCAOJW Kim 'HALUI (‘Océht‘l M meLth Pro—ggvmcoss. Ql-W 11:30 d. [2 points] For a cubic close packed metal (like gold and platinum) the location of the second peak in the X—ray diffraction pattern corresponds to scattering off planes of atoms with an interplanar spacing, org: that is exactly 1/2 the length ofthe cubic unit cell, a (as shown below). For compound #2 this peak is located at a 26 position of 44.38° (6 = 22.19°). Use Bragg's Law to determine the length of the unit cell in Angstroms. The X-rays used in this experiment have a wavelength, A = 1.54 A. d : FR :1 MEL} Ex 2.00 2 jiwe Z ($iw 1'2. \315 : 200% R Physical Constants & Conversion Factors h = 6.626 X 10'34 J-s c = 2.998 X108 m/s 1A=1Opm=1><10'10m 1eV=1.602><10'19J Approximate Wavelengths and Energies of the Visible Spectrum Violet 400-425 nm Blue 425—492 nm Green 492-575 nm Yellow 575—585 nm Orange 585-647 nm Red 647-700 nm Q1-W11:30 3 Dr. Woodward Chemistry 123 Wednesday 2:30-m- PM Spring 2008 Quiz 4 20 Minutes Name Lab Inst. Two-Digit Section Number ’— ALL WORK MUST BE SHOWN TO RECEIVE FULL CREDIT 1. [1 points] What is the difference between a substitutional alloy and an intermetallic compound? 5439 "\R \J‘ R\\ "\ , :L ‘\ Wu AIR—0M5 rméuv‘u \_ rL‘P\U.(_,¢_ M 5 MWQ & Macao-I"; xix-‘3 fim‘b_ CJ‘MFONE.‘ {q U'V\ ‘5 VWQXJLQ. \w“(méw\’&\\lg CLWVLPDUMA 3 Pt+dm5 M2- or FMgLA uA an WAJZJLLA Pod-Vex“ . ngWpcbi'\—‘LW\ I5 ‘FIKQA 2. [2 points] Describe the progression of colors as the band gap of a semiconductor steadily decreases from 3.2 eV to 1.5 eV, by filling in the blanks below. E9 = 3.2 eV Decreasing Band Gap E9 = 1.5 eV Color = \QVCA’Q. \Ig New) 0 raga? ’EQC‘; B [CLCLL/\ 3. [6 points] For the transition metal complexes below complete the following table. Compound Oxidation State Electron Coordination Coordination Confi . uration Number Geometr [Ti(H20)e]3+ Na[Cr(OH)2(NH3)4] KIA9(CN)2] Q1—W2z30 I 4. [4 points] UV-Visible spectra on two different semiconductors are shown below. Compond B absorbs light with wavelengths below 390 nm, while compound A aborbs light with wavelengths smaller than 530 nm. 10' -( E 3 .m ‘ 3 _ E E g 3 a, . a e 8 k s C. 2 4 E > -3*l 4'; 2 I :rozeno J-s Lalo) if (Sauce m 3 ° l 300 350 400 450 500 550 600 650 700 750 300 1375,4‘0’n A wavelength (nm) ' Use this data to com lete the followin table: p 9 Newbie Vl°\”}\6\% id M 9 Ma. %V‘2®V‘ Absorbs Liht lmo we» «a 2.154 a LDces v\5+ MB 54.55%“. h5g5}? ‘LDO 5. The X-ray powder diffraction pattern for NaCl is shown on the next pgé The lattice planes responsible for each peak in the diffraction pattern are shown. The EB-planes intersect neighboring planes of atoms so that the spacing between mplanes, dfi'fiis equal to the distance from the center of a sodium ion to the center of a chloride ionNThe diffraction peak at 26 = 31 .73° originates from this set of lattice planes. 2.00 a. [1 points] Use Bragg’s Law to determine the interplanar spacing, dag. The wavelength of the X-ray radiation is 1.54 A). 3"" _ ~ «x _ \ hsnrfit flax R’Z‘ifi‘v‘b ’9 a: ” I = ‘T‘Efi‘a‘s if 25:45 15qu “£3 b. [1 point] If the chloride ion has a radius of 1.81 A what is the radius of a Na+ ion? Q—vgz 5‘ : rHoJ“ (a V — Z,%Z& "rule. :Z’%Z—\°%(E\ Ql-W 2:30 C" - not l3< 45.560 0 :0 "t ‘— A 2? m o H ’5" 'E c? N 3 ' F5 l-A-. E N (\J o E O (\l {O r: O “V“ v .0 0 W4 . a I\ g V m- 0 IE 3‘ f‘ 00 o "' N OQN “3 il 00 , g 6 L081" *5 N iLN " ~_J — Ci" NCHVH ‘_ _ L: {5 co Hr‘ 20 25 30 35 40 45 50 55 60 29 (degrees) Physical Constants & Conversion Factors h = 6.626 x 10-34 J—s c = 2.998 X108 m/s 1A=10pm=1><10'1°m 1eV=1.602><10'19J Approximate Wavelengths and Energies of the Visible Spectrum Violet 400—425 nm Blue 425-492 nm Green 492-575 nm Yellow 575-585 nm Orange 585-647 nm Red 647-700 nm Q1—W2z30 Dr. Woodward Chemistry 123 Thursday 8:30 am Spring 2008 Quiz 4 20 Minutes Name Lab Inst. Two—Digit Section Number ALL WORK MUST BE SHOWN TO RECEIVE FULL CREDIT I 1. [3 points] For each of the following pigments identify the electronic transition responsible for the color: (a) band to band, (b) ligand to metal charge transfer, or (c) d to d? drug—Eirrmg‘geq Lemon Yellow, SrCrO4 fit: Cobalt Blue, C0Al204 d_ sh) _ a Realgar. A3283 baud: *0 ”kw/LA Chrome Yellow, PbCrO4 GINO? trams Fm Malachite, Cu3(CO3)2(OH)2 Cadmium Yellow, CdS Lloyd—+0 _ LAMA MC. -1 2. [3 points] CdS has a band gap of 2.4 eV, while CdSe has a band gap of 1.7 eV. Assuming one can make a continuous solid solution and that the band gap varies linearly with composition, what is the stoichiometry of the composition that would have a band gap of 2.0 eV? What color would this material be? FM“ ‘HILL scfiA Sokw‘kmk CA3 -gSQX m loco/\A <30? I5 (‘Q\05V&A to >4 flfiufik 'KMQ Ell Ouiwv-‘K‘ X _ E3cus3 — E3c'mfl __ zd’kl .— 2.6 : 5.5”? _ f - , , - E (05L 'zfil-I-W C3ficr133 «3 3 Lb: Cd SON-35¢ (3.5"! ..—-—-_______-___—‘—‘—'_—.:——d 3. [6 points] For the transition metal complexes below complete the following table. Compound Oxidation State Electron Coordination Coordination Confi . uration N—umber G_eometr IIr( (NHI (H)20 )2]( (NoeIs 3* [is] Ll?“ eab— _IC.IL m Nag[an4r4] [Cr(NH3)5S]C| Q1-R8s30 1 4. [1 points] Is the following statement true or false: All solids diffract X-rays. Fo.\%Q ,. Rnflm‘EA/UJLKS :50 \A cl“) Ac \Ao + (LR ngn'cLQJ-Y X.- rat?) 5. Each of the three pictures below represents a different type of alloy. Label each as either a substitutional alloy, an interstitial alloy or an intermetallic compound. ivik‘tfwxfiCX—ku C. 4 LL‘D‘B‘L.‘ hx‘mafl 1»x*m%¥\¥t CLQ (.LV'WX? c uwé flg w, ____________s__. D:- (LQJ'LLA Po.“'\’m MAW re,?\o..c2~m;n+ 50 \‘ikfl “mg 0 Cam 0"!— +uJo ’ngU—Qn‘k' oi? Md3m\ cadre-m LEW ~\\4\0Ln.su loévwgm airman wk{\'\’e,\) lo 3 Wu vstT:\ F3 03‘0”“ qufxovkxlrt firm/“S Physical Constants & Conversion Factors h = 6.626 x 10-34 J-s c = 2.998 X108 m/s 1A=1Opm=1x10'10m 1ev=1.602x10'l9J Approximate Wavelengths and Energies of the Visible Spectrum Violet 400-425 nm Blue 425-492 nm Green 492-575 nm Yellow 575-585 nm Orange 585-647 nm Red 647-700 nm Ql-R 8:30 2 ...
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