c123_2008_quiz6_key

c123_2008_quiz6_key - Dr. Woodward Chemistry 123 Wednesday...

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Unformatted text preview: Dr. Woodward Chemistry 123 Wednesday 11:30 am Spring 2008 Quiz 6 20 Minutes 1. Balance the following reactions using the half-reaction method. Clearly show each half- reaction for full credit [2 points each]. (a) Cr2072'(aq) + |‘(aq) —> Cr3+(aq) + IDs—(aq) (in acidic solution) be: * HH+ 4' CV1011——-> 2Cr3+ + ’7Hz,O W ‘6 Hi+ -\— C110: + 1‘ —9 ZCr $2 :03— + Auto (b) Br'(aq) + Mn04‘(aq) —> Bros—(aq) + MnOz (in basic solution) BHZO + Br’ —> Bros“ 4, (OH++ (be: 2 (35 + I—lH'+ J. MAO; —> Mnbl + 2H,,o 3 ” ZH‘l’ ‘ _‘ . - . . " no“ g + Br + 2mm04 —> zmnol+l~lbo+ 7.8.03 HLO 4- Br” + ’Z_tY\V\O._(’ -—.;> zmnol + 20H" + ZBPOZ: 2. Consider a voltaic cell based on one half-cell containing a lead electrode in contact with a soiltion containing Pb(N03)2 solution, and the other half cell containing a copper electrode in contact with a Cu(N03)2 solution. (a) [4 points] Sketch the full electrochemical cell. Be sure to label the electrodes and solutions, identify the anode and cathode, the signs of the electrodes, and the direction of flow of electrons in the external circuit. Po? «(*3 e H Lethal Bulimia") 1 €TC3VL o): Elmira (Ls 1 Flow 0": e: 1 CAA’TmAS 7% Soiwhm 1— Anocb. (b) [1 points] What is the standard emf of the cell, Eoce”, you constructed in part (a). % ($3 »——a PE7J+ 1.2,- + Oolg Cui*+?.e— -—r> Qu. +0-?)L‘ (“1,30 P505) tau“ ..—.> P‘ou—FCALQ 0-H? V 1 .fl__________.___ (c) [1 points] What is the standard free energy, AG° for the net reaction that occurs in this cell? AC3 —. -mFE = (zchcosocfl CON" V5 = galxloq 3 Cam- qc [425 - (d) [1 points] What is the emf of the cell, Ece”, if the concentration of Pb2+ ions is 2.0 M and the concentration of Cu2+ ions is 0.050 M. E :1 EL“ ~ 0.0592 Q, Q W ‘3 E =o.'~lz\/ = O-Ll’7 _ 0.08512. £00) > 2- 0.050 3. Consider the reduction half reactions for the halogens: F2 (9) + 2e" —~) 2F‘(aq) E°red = +2.87V CI2 (g) + 2e‘ —> 2Cl‘(aq) Eored = +1.36V Br2 (I) + 2e“ —> 2rB'(aq) E°red = +1.06V |2 (s) + 2e‘ —> 2l‘ (aq) E°red = +0.54V fl 1 .3, Pom-t (a) [gpoints] Which of the halogens will oxidize mercury, Hg(l)?. [A I z _ . 1+ ._ Fm em Ht) ——a H?) r 22., f: o _ _ OVCSSV k_ [:2 3 C" 1&2 hu.‘.0(\‘u*‘ I I d .- ~7 \ w (b) [1 points] What will happen when metallic Cu is added to an aqueous solution of FL ‘1 KCl? If a reaction ensues write a balanced equation to represent the reaction. 0‘7. "if";7 ’L I; vw 4. [2 points] What is the difference between a secondary cell and a primary cell? Svaxdcu—rj CQ.\\S m \o—Q Q6-W 11:30 2 Dr. Woodward Chemistry 123 Wednesday 2:30 pm Spring 2008 Quiz 6 20 Minutes 1. Balance the following reactions using the half-reaction method. Clearly show each half- reaction for full credit [2 points each]. (a) 8(8) + HNO3(aq) —> H2803(aq) + N20(g) (in acidic solution) 2- (3‘47!) 4- S "—9 HLSOg + “ll-Vr + ‘49." > <ij .+<63H++2HNO3 —-9 MLo +51HLo W HLO + 13 + “Li—h4g3} -——:> ZHL‘SOS Il- NLO (b) H202(aq) + Cl02(aq) —> Clog—(aq) + 02(9) (in basic solution) H101 "_'> 01 ‘f QH+ pla- Z ( 9:4- CADL m—-> QAOL‘ \ ’LCJO-L + HLOZ ———=—> Oi +ZC,\O.L’ + SLH" low 4 1lez+ H1014 ZOH’ Po OZJJZC’JOZ: -+ zi-lLO 2. Consider a voltaic cell based on one half-cell containing a magnesium electrode in contact with a solution containing Mg(NO3)2 solution, and the other half cell containing a silver electrode in contact with a AgNOs solution. (a) [4 points] Sketch the full electrochemical cell. Be sure to label the electrodes and solutions, identify the anode and cathode, the signs of the electrodes, and I the d irection of flow of electrons in the external circuit. 70MB 2" T..’@— Law Bush—mime 1 1 Ewan-6 of Bud-rocLI—‘s 1: k0) a”; Q) (-3 [ if? I - ' '____ Flow 0F 0.. i Cedar-ms a‘vx / ‘50\whuv\ l 1}- m my PMO do. CM (b) [1 points] What is the standard emf of the cell, Eoce", you constructed in part (a). 'u - 0 m3 ‘——r> mo) )rle, E g+2_37\/ + ’- O 2 +2. ——r—> Eg-l-ofbov Eu“: 3.317 V I (c) [1 points] What is the standard free energy, AG° for the net reaction that occurs in this cell? AC3 -:-'V\F:E -— (l0 (Clog-[$55) (3,97 3 coal >4. \0‘3 A (d) [1 points] What is the emf of the cell, Ece", if the concentration of Mg2+ ions is 2.0 M and the concentration of Ag+ ions is 0.050 M. E = 5° _ ouosal Q03 Q 1 5,17 _ 0-09312 Q0 2.0 ’VL 2. 04360 E “*5sz \/ 3. [2 points] What will happen when an aqueous solution containing Cu2+ is added to an aqueous solution containing Snz”? If a redox reaction ensues write a balanced equation to represent the reaction and determine AG° from the cell potential. '. 16+ a.“ ~=> a; + Z 5" »= +0-34 Sn“ ———=> 8mgl+ + 127 E” '1 '0“ ‘5 ____________.__.__.fl_h (Lu/1+ + 8.3+ ———'r> ( u. + 3/344, E : +OO\C‘ V . - _ 4 “Wt Ac; = - (17 (Gnome) (vo0 Lamb 4 4. [2 points] In an alkaline battery what metal undergoes oxidation at the anode? What metal undergoes reduction at the cathode? \— P‘uxfié‘a" 2n (pl—‘vz‘ /-'- I ‘70” 1:41 Zn “2‘ X * 7'": (L2, FO-{W'k— 1/ l—aHLO C9th :w‘l Care/44" $0"? = 23% \WJL: Wlw Q6-W 2:30 2 Dr. Woodward Spring 2008 Chemistry 123 Quiz 6 Thursday 8:30 am 20 Minutes 1. Balance the following reactions using the half-reaction method. Clearly show each half- reaction for full credit [2 points each]. (a) A3203(s) + N03'(aq) —> H3AsO4(aq) + N203(aq) (in acidic solution) SHLC) + A3793 #2 HBR‘DGq 4 HR" + “V: 45+ (DH*v+ —=> N193 + EHLO (b) N02‘(aq) + Al (3) —> NH4+(aq) + AlOz'(aq) Q32: + <st* + No; ~=> N144“ + rum) 2 (744,9 + m l—a (MD; + L1H“? + 39: ) W 1HJD+ no; + 294 ——=> NHL? + “1.63601 2 M03 (in basic solution) 2. Consider a voltaic cell based on one half-cell containing a chromium electrode in contact with a solution containing Cr(N03)3 solution, and the other half cell containing a cobalt electrode in contact with a Co(N03)2 solution. (a) [4 points] Sketch the full electrochemical cell. Be sure to label the electrodes and solutions, identify the anode and cathode, the signs of the electrodes, and the direction of flow of electrons in the external circuit. LCJCMPi LILLL‘F'C» Starve Alt— Euckro do}, Finis—J O? L" Cat-ims ivx 50fu Anode. (b) [1 points] What is the standard emf of the cell, Eooe", you constructed in part (a). ’2. C Cr ——r> Cry; 39:) 50= 3 ( COI++2¢- ‘—9 Co) Q6-R8:30 2Q. F 3C0“ ,azcrgfik ECO 5°: +o.‘-l(o\/1 (c) [1 points] What is the standard free energy, AG° for the net reaction that occurs in this cell? 13C; : 4M: E z — (to) Cqb)%%S>LD.4bV3 = inuos A (d) [1 points] What is the emf of the cell, Ecen, if the concentration of Cr3+ ions is 2.0 M and the concentration of Co2+ ions is 0.050 M. E ; Eo __ ocOSCt’L Q0 Q1 E0_ Q.O’ER’Z_ Q0 [Cr-3‘]?!— «t ‘3 3- VL. ‘ Q; 3 LCD 1 E : otqco - 0.05411 QC (‘L-Of- F OJ-lZV to (3 (0.0.6031) ‘ 3. [2 points] What will happen when an aqueous solution containing Fe2+ is added to an aqueous solution containing Ag+? If a redox reaction ensues write a balanced equation to represent the reaction and determine AG° from the cell potential. ROSF + 2,— —"> E‘3 : +O.%O A63‘“ FE Fe“ P.» Fe? +9: 5" ~03?! =40) (quasonDBE /’——_———d '3 u = - .9 l —> 93“ “r ’92“ “‘9’ FL?" +003 E = ODBV 2 x 0 3 4. [1 points] What is the difference between a fuel cell and a battery? 1 :L Potw‘l’ m meme (ram mat be (Lust +0 0. CD.“ ) wwm m are, COW/1&0»th in o. Q6-R 8:30 2 ...
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This note was uploaded on 06/03/2011 for the course CHM 123 taught by Professor Woodward during the Spring '08 term at Ohio State.

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c123_2008_quiz6_key - Dr. Woodward Chemistry 123 Wednesday...

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