Thermoelectroexam1011key

Thermoelectroexam1011key - AP Chemistry - Thermodynamics /...

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Unformatted text preview: AP Chemistry - Thermodynamics / Electrochemistry Exam . ,, Name: Date Period ThermoelectroExamlOll. Show all work to receive credit. Circle the letter corresponding to the best choice on multiple choice questions. There are 15 questions. ASouniv 3“ Asosurr + Asosys ASasurr : 'AHGsys/T AGO =‘- ZmAGfopmd " ZnAGR’reac; AG"rxn —RT an Eoceil = Eccathode ‘ Eoanode E z E° - (0.0257/n)an As°sys == ZmS°prod - Zn5°reaa AHO = ZmAHf°pmd ' SHAHforeact AG = AG° + RT an AG = A.st " TAssys Eocell : Eored + Eoox an = nE°/(0.0257) R = 8.31453/molK AG° == AH°sys ~ TAS‘EE,s K = °C + 273.15 F = 96,485C/mol e‘ Em" = E°ceu * (0.0592V/n)logQ ocell = (RT/nF)aneq AG° = -nFE° I = q/t 1Volt = 1joule/coulomb v = IR NA = 6.022x1023 1. Estimate the boiling point of carbon tetrachloride given the following thermodynamic parameters. AH‘KKJ/mol) S°(J/Kmol) AG°f(kJ/mol) fig; as 5; £3; C040) -128.4 214.4 -57.6 g, h” g v m mag) -96.0 309.7 53.6 53* we re, e 37% Work Area: «a if}; f 65,; . W... rice e W V r 55 E :5"? » y if :33? wT/Zee’éfie; Answer: 3133353 g °C ’7’? “35?: “if? 9’: We”; fly 2. Use the following thermodynamic data if “"i 6’55? g“? ‘5‘” AH? (id/moi) S° (J/Kmol) H2020) -187.78 109.5 H200) -285.83 69.91 02(9) 0 205.14 To calculate AS"...v for the decomposition of hydrogen peroxide at 230°C. g 1%? 2H2020) -—> ZHzog) + 02(9) we- 25! ; {Eggeees :: "If? a; ‘ * I ’ » Q’ .1 *9? w°rkA'°a' foresee-t tfeegg 59553 e .2: {may :53; 3 fig 7;. 32,: 2 ‘ €13 {E f, E as “r Q 9:5“; 2; “fight so? 4% Answer: a?) g 5* 53 J/K _ f M 5. A ,- see We 3. Consider the reaction gags g.ng a: ,2 {3! if. g 2POCl3(g) -> 2PC|3(9) '1‘ 02(9) ’ U ’ a. Calculate AG" for this reaction. The AG°f values for POCl3(g) and PCl3ég) are ~502kJ/mol and —270.kJ/moi, respectively. 2%? to Q 3:64.; ‘3 w a, w m _ w é, Work Area: { $7 “Ma/‘5 5 M ( “‘3 Q: gigging.) 2: é’éc’f’s‘éj” E. s" [g Answer gé f K! b. The value of AS3 for this reaction is 179J/K. What is the threshold temperature (in K) at which this reaction becomes spontaneous at standard conditions? Assume that AH" and 135° do not depend upon temperature. TEMX: Tagger? if}; M , {El/gages ; earet‘ s if“ V K a? fig?“ as. W t; we {’3 ' Answer: WK e ii e S? assets delegate are e??? o :Ki"?.§?i:§r “tiereees’feé its! 4. Ethanethiol (CZHSSH; also called ethyl mercaptan) is commonly added to natuiiai gas to provide the “rotten egg” smell of a gas leak. The boiling point of ethanethioi is 330°C and its heat of vaporization is 27.5kJ/moi. What is the entropy of vaporization for this substance? Work Area: eiééw’gész 2’? at: as“ v e 3?? gen: ire? innit 3833..» g Q ,_ or é 2e.“ % (:3? w ‘4” g; . g“ :ggféwfg i"; w iéy 2'" Answer. J/molK v3 w Zszfiegmsfgmg If: grief, 23/Vgg ' Qggz‘ég :1 w 33$“ ’3‘” 5. Cells use the hydrolysis of adenosine triphosphate, abbreviated as ATP, 35 i’ng§ce of energy. Symbolicaiiy, this reaction can be written as ATP<aq) + H200) —-> ADPQQ + H2PO4‘(aq) Where ADP represents adenosine diphosphate. For this reaction AG" == *305kJ/moi. a. Calculate K at 250°C. at WorkArea: Agree a“??? m e ,, it: gs”! *‘lth" ggféit: Answer: A L“ g a? \ s b. If all the free energy form the metabolism of glucose (C5H1205(s)) C5H1205(5) + 602(9) -> 6C02(g) + 6H20(1) goes into forming ATP from ADP, how many ATP molecules can be produced for every molecule of glucose? (Standard Gibbs free energy of formation (kJ/moi): CGHQOSG) z -911; COM) = -394; H200) z —237) Work Area: e W I disorng égjsfigfimgs egg; : era/7? let 225; ; "Eff; .1??? 3‘: 3 iii «3:. f5” 3 w fie; a? Answerg‘ “" is. ATP molecules 6. Calculate E for the following electrochemical cell at 25°C Ftp) i sn2+(aq,0.50 M): sn4+(aq,0.50 M) H I'(aq,0.15 M) l AQI(s) I A9(s) given the following standard reduction potentials. ) ME}; 4% g Z'Agloi +35 mums) +lI—(BQ) E° = -0.15V t3” {it “we ‘3’“ it :13: «trite/J 4’ 5n“”<aq> + 2e‘ -> snz+(aq) E° = +0.15v are M Work Area: fine” a} , me u. r: g . “W 3%»? fixmésw fafm {first g?” .9 if? i tééeeesi see its 5%}??? % JV?” iii; 42W}? 513;; , ’1‘ : «REE; 7. What is the pH (pH = -log[H30+]) of the solution at the cathode if Ecen = —0.174 V for the following electrochemicai cell at 25 °C? ,, ,, ,,,,,,,,_pt,,,l,,H2(gt,lioam,,l, Htmgmgm,,i,,!,,,,,H+(aq), {Moria 1G,,éfm),,,,l,,,_,pt,, ,, _, ,,,, _, , ,, ,, , Work Area: ‘ I 5:; bflfggw 5;;fig)?é§géfi) “’“r’g‘” W5} JW~€2§§3 , f ggiaagefigxge f, :Efigifi’igxe} eees3¢,§g:~ix if? Q2 4?? K “ Answer: - 8. Calculate AG" for the disproportionation reaction of Cu“ at 25 °C, X :1? , fiififaeg’? it? @543 2CU+(aq) *9 CUHQQ) _ + (11(5) ’ g 5' Jr»; s 3 r 3" a t , given the following thermodynamic information. w i for”? 5 rift 5 * tie? “a; 3?] er 2.: 2[7/ or)”; + e‘ —-> Cum ° = +0.518V tie? ‘3 CU2+(aq) + 2 e" --> Cum 0 3 V ‘j Work Area: I f g g ‘ 4,, M f M f? if” ow ; ~ M t Answer: a” Egg?“ k] 3: effigy gr 9. Calculate the equilibrium constant for the following reaction at 25°C, C°2+(aq) + 2 Guam * Cots) + 2 Cr3+raq) , :2 given the following information. f gee” 55%;?) ’5” , y; to es : g3 COZ+(aq) + 2 e‘ -> C05) E0 =: g a; i ‘3 y I Cr3+iaq) + e- —'* {324.8(3) E0 = V f $5.63 5 w Work Area: § figs? w \ _ e [159; disf?) g: ? gait a, go are? is : geese? ,3 agree}; i " agile??? ’i’ Answer: 10. One kind of battery used in watches contains mercury(II) oxide. As current flows, the mercury oxide is reduced to mercury. _ H905) + H200) + 28' —> Hg“) 4' 2014.911) If 2.5 x 10'5 amperes flows continuously for 1095 days, what mass of Hg(.) (in grams) is produced? Work Area: _, a , a r . a; : i’fifl‘f 5 32%“) a?“ figéfiie a meagre iiagié ‘ ‘ é“ ' iér a r: -r t? t I, _ rig Zé’x‘go C: 5 {frieze/re 5:3) f: a” j“? g" eitrgs-eemi «2 j p § 2: V V t ‘5 s a? 5;" eras {2/ get if: if 5% mg i, istiizéei Answer: is __..__9 J; “ 3m ‘“ i gig, 6:. 29, g, 11. Write a balanced half-reaction for the reduction of Cl03'(aq) to 02(9) in an acidic solution. g a fa, 12. For a chemical system, AG" and AG are equal when £5 a. the system is in equilibrium ,, , ,, ,, ,, ,, , , , , , , , c. the equilibrium constant, K, equals 0 y 9 7 d. the reaction quotient, Q, is less than 1 % you «I a“ ’ e. the reactants and products are in the gas phase Z 13. The following reaction is endothermic 302(9) ——> 203(9) The reaction is . spontaneous at all temperatures non—spontaneous at all temperatures c. spontaneous at low temperatures cl. spontaneous at high temperatures i} 45;} if WEE“; 7 14. With respect to electrolytic and galvanic cells, which of the following statements about these cells is correct? a. The anode will gain weight in a voltaic cell. g b. Oxtdatlon occurs at the cathode of both cells. L 5%; gfig Mama; gases-e @The free energy change, AG, is negative for the voltaic cell. d. The current flows from cathode to anode in an electrolytic cell. 15. Use the standard reduction potentials below to determine which element or ion is the best reducing agent? Pd2+(aq) + 2e“ —+ Pd(s) E° == +0.9ov Sn2*(aq) + 2e‘ w» 5%) E° 2 —0.14v CT2+(aq) + 2e' -> CH5) E0 = a. Pd2+(aq) b. Pd 5) C- 5” +(an) d 0'27”) r(s) ...
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Thermoelectroexam1011key - AP Chemistry - Thermodynamics /...

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