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ch15homewk_10 - 660 Chapter '15 I' Chemical Equilibrium...

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Unformatted text preview: 660 Chapter '15 I' Chemical Equilibrium VISUALIZING CONCEPTS I’ll (.1) Based on the following energy profile, predict (Q whether .lcf- 3-- lr, or it, C it... (l3) Using Equation 15.5, predict whether the equilibrium constant for the process is greater than 1 or less than 'i. [Section 15.1] Reactants Potential energy _ Protl ucts Reaction pathway 15.2 The following diagrams represent a hypothetical reac- CQ tion A -—r B, with A represented by red spheres and B represented by blue spheres. The sequence from left to right represents the system as time passes. Do the dia- gt'tuns indicate that the system reaches an equilibrium state? Explain. [Sections 15.1 and 15.2] 15.3 The following diagram represents an equilibrium mixture to produced fora reactionof the type A + X .—— AX. lt'lhe volume is l L, is K greater or smaller than 1? [Section 15.2] 15.4 The following diagram represents a reaction shown (Q going to completion. ta) Letting A - red spheres and B = blue spheres, write a balanced equation for the re- action. (b) Write the equilibriu 111-C0l15lflnt expression for the reaction. it) Assuming that all of the molecules are in the gas phase, calculate Air, the change in the number of gas molecules that accompanies the reaction. (d) How can you calculate KI. if you know K‘. at a particular lem~ perature? [Section 15.2l e. ° 9 0 '2'? Q 0° ‘9 6' 15.5 The reaction A; + B; = ZAB has an equilibrium CQ constant K. = 1.5. The following diagrams represent 11;. action mixtures containing A3 molecules (red), 33 mole~ cules (blue) and AB itioleeules. {3) Which reaction mixture is at equilibrium? [bl For those. mixtures that are not at equilibrium, how will the reaction proceed to reach equilibrium? [Sections 15.5 and 15.6] 15.6 The reaction f\2(8) + 3(3) '~:‘ Age) + Alilg) has an CQ equilibrium constant of K‘. -" 2. The diagram below shows a mixture containing A atoms (red), A; mole— cules. and AB molecules {red and blue}. How many 5 atoms should be added to the diagram if the system isat equilibrium? [Section 15.ti[ The following diagram represents the equilibrium state for the reaction A233) + 2 Big} : 2 ABIEg}. la} Assuming the volume is i L, calculate the equilibri- um Cunstant, K, , for the reaction. (bl it the volume offhfi equilibrium mixture is decreased, will the number of AB molecules increase or decrease? [Sections 15.5 and 15.7] }It at 15.5 i'.\:I till? 1512 15.14 The following diagrams represent equilibrium mixtures for the reaction ."\-_> + ll 2 A 2- ABal [H.100 Kancl [El :30” K. The A atoms; are red, and the it alums are blue. is the reaction exotl‘ierniic or entiothern‘tie? lFit‘L'tion 15.7] Eiirl-IRCISES Equilibrium: The Equilibrium constant Suppose that the gas—phafit‘ reactions A r it and t5 -- -' A are both l-fltflt‘ttftll'flt‘y proceHHeH with rate con— stants of 3.8 X ll] ‘l' 5-; 1 and 3.1 K in '5 ', rt!HIJ(.‘t'll\'L.‘l}-’. (a) What is the value of the equilibrium crane-itanl for the equilibrium Wig) ' ‘ 3(3)? (b) Which is greater at equilibrium, the partial [Wiftw‘filll't‘ of A or the partial pres-i- SLII‘L‘ of B? Explain. Consider the reaction A + it .—‘ L: t I). Assume. that both the forward reaction and the I'CVL't'E-L' reaction are elementary processes and that the value of the equilibri- um conHlant is verv large. (a) Which species predomi- nate at equilibrium, l'('i!t'l'ill‘|lfi or products? (11) lNhieh reaction has the larger rate constant, the forward or the reverse? Explain. {at What is the late ty'miiss action? Illustrate the law by using the NUtg} -t- llrgi‘e) NOBrgtg). lb) What hi the difference between the equilibrium constant empression and the equilibrium constant tor a given equilibrium? (c) Describe an experiment that Could he used to determine the value of the equilibrium constant for the reaction in part tn}. (al'l'he il1t’t'l'ILIIIh-il'l't for a certain reaction A 'i- ll- v—‘ reaction C + I) is unknown. L‘s it htill Put-itilbll: to apply the law of mass action to the reaction? Explain. ([1) Write the chemical reaction involved in the l-iaber process. Why is this reac— tion important to humanity? [cl Write the equilibrium— mntttant expresrdon for the reaction in pa rt (h). Write the expression for ix".- for the following l1?iit‘llntt.‘~'. in each case indicate whether the reaction ib homoge— neous or heterogeneous. [a] 3 Mom .2- more) + Mom) (bltfliiw) + rinse) :—-* trsgrg) + Jillng’) (cl Niicoim :2 man i more) [Lil l'thiq) ._—9 Him?) -‘ F {on} (e) 2 Age.) + Engine) 2 Ag‘tmg) + Znisl Write the expressions for K‘ for the following reactions; in each case indicate whether the reaction is: homoge— neous or heterogeneous. (a) N2i.'~ll ' Oztitl =15 2 Note} [blTiis] + 202(3) :‘ TiClfll} (c) 2 C21 his) + 21130“) 2 '2 Cgllfitg} 03(3) 15.16 I‘LI'} 15.13 I3.I‘J 15.20 1.5.22 66'] Exercises [d)lie0{s) i Hylg) .—' Felts) + ilgOLe) ta) 4 HCltmi} + ogre) 2 i-lgt)(i) i- mag} '3 When the following reactions come to equilibrium. does the equilibrium mixture contain mostly reactants-i or most- lv products? (a) Nag) i Gate) ‘ ‘ ZNOLeiflq -- L5 x It] "' (MZSOELQ) Ogtg) 2501fgl; K?” = 2.5 x it)" Which of the Following reactions lies-t to the right. favor— ing the formation of products, and which lien to the left, favoring formation of reactants? (a) 2 More + 03(3) mom); KP — 5.0 >< to” (bl21ilirtgt :- 113(3) Bl'gfg); K,. = 5.3 x in “i it K‘ = till-l2 for l’(ll3(§) -l (13(3) .—" i‘(_‘l5tg)nl 5(ltl K, what is the value of K1, For this reaction at lhira temperature? Calculate K,.at3tt3 K i'orSOzte) + Clglfs’} ‘42 SOzCl-At‘e) if K... = 34.5 at this tel‘t‘ipel’t‘ituie The. equilibrium confitant for the reaction 2 worst) +— iii-2(3) = 2 NOBri’g) i5 it". ; 1.3 X it! 2 at ltitiU K. (a) Calculate K. [or 2 hit—Jitter) : 2 NOqu + Brag). (bl .-'\I Ihlt-i tempera— lure t‘ltiL‘S Ihe equilibrium Favor NO and iii}, or riot-5 il favor NUlir? The equilibrium constant for the. reaction 2 Note) i (32(3) 2' 2 NOEL-q} i5 KP == i518 X ltl'i at I84“C. (a) Calculate Ki. for 2 NORt‘q'} .——' ZNUW} t (32(3). (b) Does-s the et‘luililirinln tavor NO and 02, or does it favor NC}? at this temporal-em? At 1000 K. K.-. —- l.85 For lhereaction sage) + teat) 2 State (a) What is the value (it K3. tor the reaction 503(3) «——‘ Ste-33(3) '4' £0“)? (b) What it; the value ot K“. for the reaction 3503(3) + (Mg) : ZSOfi‘e]? (C) What is the value of K‘ for the reaction in part (b)? Consider the following which K}, — 0.0752 at 48th:: equilibrium, for 2mm) a 21—hour 411cm 03m} 662 [15.24] Chapter '15 l Chemical Equilibrium (a) What is the value of K“ for the reaction 4110(3) + (Jag) :- zctag) I 2 room)? (b) What is the value (it it}. for the reaction Chile} + Hgl Jig) 1—‘ 2 l'lCtlg) 4 02(3)? (c) What is the value of K... For the reaction in part (b)? \ Consider the reactions Man) + Blnq) r—I Chair) and C(ari) + Dtriij} .—= titan) | Atria} for which the equi- librium constants al 'lULl"C are K. m [.9 X It.) 4 and ti.- 3-5 X “1'1; Tl‘Sf‘N‘ftth‘ty. What is the value. of K. for the reaction than) I Dotti} A Ruin)? Consider the equilibrium Nzls] i' Oats.) r mitt) ~—'—‘ 2 NOBI'tk’i Calculate the equilibrium constant KI. I'or this reaction, given the Following infom‘tatit‘m [at 298 K): 2 NOm) + Iii-gm :4 2 Non-(g) K. 2o 2 Note) = um} -i- 02(3) K, 2.1 x 10”” Calculating Equilibrium Constants 15.23 15.30 |"'i.'il [335 15.36 » Gaseous hydrogen iodide is placer] in a closed L‘ou— lait'Ier at 425°C. where it partially decomposes to hy- drogen anti iodine: Zillfg} = llzlg) t trig). At equilibrium it is found that [Hi] 3.53 5‘: it) 3M. [H2] ~ 4.70 x ttilrtri,c1t1cl[12] = 4.79 X t0"tM. What is the value of KE at this temperature? Methanol (Cl-l3t')l-l) is produced commereiallyr by the catalyzed reaction of carbon monoxide and hydrogen: COW} 'r 2 Hz 3*) :‘ Cl-I3Oi-i(g). An equilibrium mixture in a 2.004. vessel is touuel to contain [104-th mol Cl-hOl-l, tt.'t?tt mol CO, and 0.302 mol H; at 500 K. Calculate K( at this temperature. The equilibrium 2 NOQQ) + (313(3) ;——‘ 2 NOt'flitg) is established at fittt) K. An equilibrium mixture oi the three gases has parlial pressures nl't].ll‘15 atm, U.1?l atm. and 0.28 aim for NO, Clg, and Not], respectively. Cal- culate KI, for this reaction at 500 K. Phosphorus lrichloride gas and chlorine gas react to form phosphorus pentachloritle gas: I‘Clgtg) CH3} 2 I’Clqtgi. A gas vessel is charged with a mixture ol' PCl'gl‘Q) and C1291), which is allowed to equilibrate at 450 K. r\t equilibrium the partial pressures of the three. gases are PM}; = O.|2al atm, i’g], = 0.157alm, and Pm H -- 1.30 atm‘. (a) What is the valia- ol K], at this tem- perature? lb) Does the equilibrium t'avor reactants or pi‘t'idut'ls? A mixture of it'll] mo! of NO. [LUSH mol of | l2, and 0.11.] moi of I IZO is plated in a J.D—L vessel at 300 K. The fol— lowing equilibrium is established: 2N0t‘g) I Zl-igtq) .——_~ Nam} -: 2 Hattie) 4 Applications of Equilibrium Constants it‘ll llow does a rt's'itftit'm quotient diller from nu equilib— rium constant? (1)) if Ql. *3 K. , in which direction will a reaction proceed in order to reach eqiiiliirrrium? (c) What condition must be satisfied so that Q. = lg? [21) l low is a reaction quotient used to determine whether a system is at equilibrium? (1)) ll Q. 3* Kr, how H.133 15.26 15.32 15.34 Mercury“) oxide clmomposes into elemental met-cu“, and elemental oxygen: 2 i-lggots) Z“ 4 l igtt) t— 02(5ng (a) Write theeqnilithium—constantexpression For this re- action in terms ot' partial pressures. (b) l-ixpiain why um‘umlly exclude Pth'L" solids and equilibriummconstnnt expressions. (.‘onsider the equilibrium NagOls‘i t- State) :2: Nag-801(5). ta) Write the equllitu-inm—constanl cXpres- Sion for this reaction in terms ot‘ partial [mussel-Ge (b) Why doesn‘t the concentration of NagO appear in the eqiiitihrium-constaut expression? I “'13 liquids {mm Al equilibrium INU] — tliiol M. (.1) Calculate llie. equj. libriuin com-entrations of Hg, N3, and llzt). (b) Calm. late K. A mixture of I37”! 3 of Hg and 7t]..."lt 3; ol' Br; is heated ina 2.t]—| . \‘essel at FUD K. These substances react as follows: Hat} I- lil'gtg} = 3 Hart?) At equilibrium the vessel is found to contain [L566 g of l t). (a) Calculate the equilibrium concentrations of Hg, l‘n'g, and l—lBr, lb} Calculate Kt” A mixture of 0.200“ mol ul C03, {Lllltltl mol of 113, and 0.1 tint} mo] of | lat) is placed in a ZUUU—l- vessel. The Feb {owing equilibrium is established at Still K: €0qu -I- the) = L'Otg} i HgOij‘) (a)(..'alcu|ate the. initial partial pressures of (302,1-12, and H20. (b) At equilibrium t’lho = .'?-.5| atm. Calculate the equilibrium partial pi'esstii'es ot‘ COL H3, and CO. (c) Calculate KI, tor the rt-Iactior‘t. A flask is charged with lfstlt]I atm of Myth-{g} and 1.00 atiu Mom) at 25"C, and the Following equilibrium is achieved: Niche) .— 2 N02t a After equilibrium is reached. the. partial pressure of N03 is 0.512 arm. (a) What is the equilibrium partial PI'DSSLU‘C 0t N204? lb) Calculate the value ot' Ki. tor the reaction. must the reaction proceed to teach equilibrium? {cl At the start of a certain reaction, only reactants are present; no products have been Formed. What is the value of Q.- al this point in the reaction? At |tJtl°C the equilibrium constant for the reaction col-tight) : (Ute) + Clglg} has the. value K‘ = 2.19 x [U “K Are rm.- following mixtures of (iotiig. co. 15.38 15.40 ISL-12 121‘ and Ct; at IttU"C at equilibrium? if not, indicate the direc- tion that the reaction musljaruceed to achieve equilit‘irium. (a)[(‘.(.)CI_1_J —- 2.111] X 111 " M, ](_‘O| -"— 3.3 X it) " i’vl, |t2131 — 5.52 :< iii "‘ M; {b} [eoeigi 4.in >< lit 1:14, |(.'o|- 1.1 x 1117M, mat — 2.25 x 111 1’ M: (c) ECC)C1:| — {1.011111 M, ICU] — ICIZl « 1.48 x it) 1‘ M. As shown in Table 15.2, K,. for the equilibrium Nam) + 31-13(53) _ 2 Ail-hm] is 4.51 X 10 5 at 45051.7 For each of the mixtures listed here. indicate u-‘hether the mixture is at equilibrium at -1511“C. If it is not at equilibrium, indicate the direction [town rd product or toward reactants) in which the mix- ture must shift to achieve equilibrium. (at 105 atm N113, 35 atm N2, 495 atm 113'. (b) 35 atm N113, 595 atm I 13. no N3: 1c] 2s atm N1 1;. =12 atm 113, 2112 atm 1 3. - At 'lt1t1"C, K, tJ.U7ti for the reaction 50120260: some Cue in an equilibrium mixtureol the three gases, the conten- [rations of 505.112 and SD: are [1.1138 M and 11.11.512.14, re- spectively. What is the. partial pressure. of Cl; in the equilibrium mixture? At UtIti K the following reaction has K!” = [13-15: lab“) _. 03L“) ,,.-_- 2 503(3) In an equilibrium mixture the partial pressures of 503 and (33 are U. 165 atm and [1.755 aim, respectively. Whal is the equilibrium partial pressure of 50-; in [he mixture? [31 At IESSCC.‘ the equilibrium constant for the reaetion lirzte] 2 Bligh is K, 4 1.114 X lt‘l 1. A (1.21111-1. vessel containing an equilibrium mixture of the gases has [12-15 g Brztgt in it. What is the mass of Brie) in the res— sel? (b) For the reaction Hzre) + 12(3) ‘—‘ 31 111(3), K, = 55.3 (1171111 K. in a 2110-1. flask eontaining an equi- librium mixture of the three gases, there are (1.1156 g H: and-1.36 g 12. What is the mass of 1-11 in the flask? ta) At SUU K the m‘Liiilibrium constant for 11m) = 2 lie) is K, 3.] X Jtt 11' an equilibrium mixture in a [tut-1. vessel eontains 2.67 X it} g of [(3), how many grams of 13 are in the mixture? (IJ) For 2 503(3) I Ullls‘r} : lSt'ht‘e), K,,. = 3.11 X 111" at ?'11{1 K. In a 2.t1t1—1..\'esse| the equilibrium mixture contains 1.5? g oI'SC1-,a|1L111.12-.“i 1.; of ('12. How many grams off-‘10: a re in the vessel? At Etltitic'C the equilibrium constant for the reaction 2 Note -= Niel + this) Le Chitelier’s Principle Consider the tollowini; equilibrium, lor\\'hie1‘t AH ~3 [1: 250m) + 03b?) -—‘ 2 Soto) | low will each of the Following changes affect an equi- librium mixture of the three gases? [at Ogt‘e) is added to the system: (b) the reaction mixture is heated: (c) the volume of the reaction vessel is doubled; td) a catalyst is added to the mixture; 19) the total pressure of the system 15314 15.1% 15.46 "15.48 |=..-1u 5.50 15.52 Exercises 663 is K, -- 1-1 X H1“. If Ihe initial eoncentralion of NO is t1.2UU M, what are theequililu'ium concentrations of N0, N2, £11151 tor the equilibrium iii-2(3) + (13(3) = 2 Iii-elm (it-IOU K, K. '—- 7.1).1fll.3t1molot15r3 and [1.30 mo] C1; are introduced into a 1.0—1. container at 11111 K, what will be the equililn-ium concentrations of Beg, C19, and WC]? A1373 K, K]. 1-' t1511ti1'orthe equilibrium 2 Moist-(x) _-* 2 now. 1- iii-30¢) 1f the pressures: of NOBrt‘e) and NOtle) are equal, what is the equilibrium [Tiret-IsUI'Ll ot Bulge)? A1 2181', K, = 1.2 X 111 '1 for the equilibrium NH.,HS{5} = also) I i-igsigi Calculate the equilibrium concentrations of NH; and 1-138 if a sample ot solid Nl-lal-IS is placed in a closed vessel a mi decomposes unlil equilibrium is reached. x Consider [he reaction (:nsoas) :——_- (in-ting) + 50,3 (my) 1\t25"'C the. equilibrium constant is K, -- 2.4 X it] ; tor this reaction. (a) 11' excess CaSO.,ts} is mixed with water at 25°C to produCe a saturated solution of CaSt'tl, what are the equilibrium concentrations of Caa' and 5042 ? lb) if the resulting solution has a volume 013.11 1., what is the minimum mass of CtiSL'J;ts) needed to achieve equilibrium? .»\t'SU"'C. K, == 1.8? x it] '1 for the reaction l’l-lilit'ttts} .: Whig] + new) (2!) Calculate the equilibrium concentrations of 1’1 1-: and BCl: if a solid sample of PH tliCl; is plaCecl in a closed vessel and decomposes until equilibrium is reached. (1.1} [t' the flask has a volume of [1.500 1., what is the. mini- mum mass oi 1’1-1311(:i_1(s) that must be added to the flash to aehieve equiiibriuln? For the reaction 13(3) 1- Brie] :‘ ft. llirLe), K, -- 2511 at l.'3[1“(‘. Suppose that 1.1.500 moi 1111‘ in a 1.1111—1. flask is allowed to reach equilibrium at 13111:. What are the equilibrium colleentrations ot itir, 13, and Lil's." At 25"C the I'euelion CaCrE'tlts} :" Cal'ith} -i- {CI-Oil (riff) . . . __ . .i has an equilibrium constant K, “ Li X 111 . What are . . . . . ., J. t 3. . the equilibrium eom‘entrations of La” and (.104 In a saturated solution of Cat; rtll '3 is increased 13:5 adding a noble gas;if)55111313)isreinoved treat the system. For the following reaction, .111" =' 2816 k]: («roam + n I igom v—~ (,1 1130.415) -1- s (13(3) How is the equilibrium yield of Chl'lmOh affected h_\' (a) ii'ua'easini,’s Pm“ ([1) increasing temperature, tc) remor- ing C02. (dielecreasing the total pressure, (e) removing pa r1 of the Chi-1130“, (F) adding a Calatyst? 664 15. 5.1 15.54 . .LT.‘ Chapter '15 | Chemical Equilibrium How do the following changes affect the value of the equilibrium constant {or a gas—phase exothermic reac— tion: (a) removal of a reactant or product. (bl decrease in the volume. 0:) decrease in the temperature. {dl acidi- tion ofa catalyst? Fora certain gas—phase reaction, the fraction of products in an equilibrium mixture is increased by increasing the temperature and increasing the volume of the rear:- lion vessel. in) What can you conclude about the reaction from the influence of temperature on the equi- librium? (b) What can you conclude from the influence of increasing the volume? Consider the lotion-'ng equilibrium between (Hides oi nitrogen 3 NOQQ) .—‘ NOELQ} -.- Ngotg) Additional Exercises HS?" 1 5.53 15.50 15.6] Both the forward reaction and the reverse reaction in the following equilibrium are believed to be elementary steps: cote} i- Ciztgi = CUCHX) + (31(3) At 23°C the rate constants For the forward and reverse reactionsare [A X 10 15 M' [5' 1and 9.3 X ltlmi'vl 's ", respectively. (a) What is the value for the equilit‘iriuiu constant at 25"‘C? (13} Are reactants or products more plentiful at equilibrium? A I'nixture. of Cl |.1 and HBO is passed over a nickel cata— lyst at 1000 K. The emerging gas is COIlCt ted in a 5.tlt.]—l_. flask and is found to contain 8.62 g of CO, 2.60 g oi Hg, 13.0 g of CHJ. and {18.4 g of H10. Assuming that equi— librium has been reached, calculate Kt. and it}. for the re.- actlon. When 2.00 moi of 50303 is placed in a 2.004. flask at 303 K. 56% oi the 50202 decomposes to $03 and Clz: w: 'l' Calculate Kt. For this reaction at this temperature. A mixture of l l2, '5, and H38 is held in a l.0-|. vessel at 90°C until the following equilibrium is achieved: I13qu + so) . _* “35(3) At equilibrium the mixture contains 0.46 g of H254, and 0.40 g Hz. {a} Write the equiiibrium—constanl expression tor this reaction. (bl What is the value of K. For the reac- tion at this temperature? (c) Why can we. ignore the amount off? when dong the calculation in part (b)? A sample of nitrova bron'ticle (NOBr) decomposes ac- cord ing to the equation 2 NUBqu) .—_~ 2 Note) * Bragg) An equilibrium mixture in a 5.0il-l . vessel at 100°C con— tains 3.22 g of NOIir, 3.08 3 ol' i‘x-‘tl. and 4.19 g of lira. (a) Calculate K, tbl What is the total plessure exerted by the mixture of gases? Consider the hypothetical reaction Mg} ‘——‘ 2 Big). A flask is charged with 055 atm nl'put-e A, after which it is allowed to reach equilibrium at 0°C, At equilibrium the partial pressure of A is 0.36 atm. [a] What is the total 15.56 "t 5.63 [5.64 [15.67] lit’iH (a) Lise data in Appendix t.‘ to calculate _\H"' For this W. action. tb) Will the equilibrium constant for the reactio“ increase or decrease with increasing temperature? l-jx. plain. [c] Atconstant temperature would a change in the volume of the container affect the traction of products in the equilibrium mixture? Methanol (Cl-l 10H] can he made by the. reaction of CO with H2: COW + 2 Hm?) .—_‘ Cl I30] 1(3) (a) Use thermochemical data in Appendix C to ca lculak. Jill“ for this reaction. (1)) to order to maximize the equi. tibrium yield of methanol, would you use a high or low temperature? (CI in order to maximize the equilibrium yield of methanol, would you use a high or low pressure? pressure in the Flask at equilibrium? lb} What is the value. of KP? As shown in Table l5.2, the equilibrium constant for the reaction Nate) + 3 Hag!) r: 2 Ni‘igl‘fi") is K}, = «1.34 X it] " at 300°C. Pun: NH; is placed in a LOU—t. flask and allowed to reach equilibrium at this temperature. There are 1.05 3 NH; in theequilitu‘ium mixture. (a) What are the masses of N2 and Hg in the equilibrium mixture? (b) What was the initial mass of ammonia placed in the vessel? (c) What is the total pressure in the vessel? For the equilibrium 2 Ii'h‘t‘e) : lgi‘g} -'i- lirgfiq) to -—- 5.5 x m 3 at 'I5[}"C. It tries aim of II-ir is placed in a 2.0- L container. what is the. partial pressure ol' this sub— stance al'ter equilibrium is reached? For the equilibrium l’HgBClJlHl = Plum + 130m.) KI, — 0.052 at {1013. {.1} Calculate K... (11} Some solid PHRBCig is added to a closed 0.5UU-l. vessel at 60°C; the vessel is then charged with 0.0128 moi of BCl-itx). What is the equilibrium etnicentratlon or l’t-h? l15.66I Solid .=\‘-| til-l5 is introduced into an evacuated llask at 24"C. the following reaction takes place: Nli.;l-IS(::} :_-‘ NH“) + “38(3) At equilibrium the total pressure {for NH; and H35 taken together) is 0,614 aim. What is KP For this equilib- ri u m at 24%? _ A 0.83'I 1; sample oFSOi is placed in a Lilli-L container and heated to l'ifltl K, the SO} decum poses to $02 and 01: 2 50300 :‘ 2 5020:) + 02b!) At equilibrium the total pressure in the container is [.300 atm. Find the. values of KI. and K, For this reaction at Iiilll K. Nitric oxide (NO) reacts readin with chlorine gas as follows: 2 Note) i (:12th 2 NGCILe) r_ it? ii- iii ‘Il -? 0 ___J '| 5.69 1530 ('0 lTS.72l At 700 K the equilibrium constant K“, for this reaction is [1.26. Predict the behavior of each of the following mixtures at this temperature: (all-{o0"tl.|5al:1‘i, 1-1: = [13] atm, and item-l [1.11 aim; [hi Pen — n.12atm, it ii = it'll] atm, and PM,“ = Uilfitiatm; (C) P“; == tilSatm, i’L-l, T tiltiatm. and PM“ —- 5.11) X It] "aim. ‘ At 9001', K‘. — 0.0108 For the 1't.‘actioi't CaCUnis) C'ans) -i- (CO-3(3) A mixture of CHICO]. C610, and C02 is placed in a lilil-l. \‘essel at ‘JtltlL‘C. For the lotion-in}: mixtures, will the. amount of CaCU‘ increase, decrease, or remain the same as the system approaches equilibrium? (at 15.01; CaCCh, 'i'Sti g CaO,a1u| 4.2': E (‘0. (b) 2.50 g Cacoj, 25.0 g Cat“). and 5.66 g CO: (C) 30.5 5; Cocoa. 25.5 e. (.110, and {1.48 33, C033 Nickel carbonyl, Niiiftm. is an extremely toxic liquid with a low boiling point. Nickel carbonyl results from the reaction of nickel metal with carbon monoxide. For temperatu res above the boiling point (42.2“CJ ot- NitCOh, the reaction is Niisl + icing) ._- Nirconu) Nickel that is more than 999'?” pure can be produced by the carbonyl process: Impu re nickel combines with Ct) at 5[}"‘C to produce .I IiiL‘UMSJ. The NiiL'Uti is then heated to 2t]li"i..‘, causing it to decompose back into Ni(::) and (Dig). in) Write the cquiiit‘rriLint-constant expression for the formation of Niicoli. (b) (liven the temperatures used for the steps in the carbonyl process, do you think the lormation reaction is endothermic or exothermic? (C) in the early clays of aLiton‘iobiles. nickel—plated ex- haust pipes were usecl. Even though the equiliL'nriLim constant for the formation of XiiL‘Uli is very small at the temperature of automotive exhaust gases, the exhaust pipes quickly corroded. Explain why this occurred. NiO is to be reduced to nickel metal in an industrial process by use of the reaction Nit‘im I coig) Niis) com») At 1600 K the equilibrium constant for the reaction is Kg. —' an X 1t12. It' a (.1) pressure of IEU [err is to be employed in the furnace and total pressure never ex- ceeds 7M] torr, will reduction occur? {\l. Fill} K the equilibrium constant for the reaction L‘Clii‘e) ~:" C(si -=- 2Clgt‘e) is Kr = [1.76. A flask is charged with 2.00 aim at {III}, which then reaches equilibrium at 700 K. ta} What frac- tion of the CCI; is converted into C and L13? (1)) What are the. partial pressures of CCl.-, and Ct; at equilibriul‘n? ll5.'?3] The reaction |’C|;;{gi l Clgi‘e} .——‘ i’Cline] has K“. = illitt'i’ti at 3003C. A flash is charged with ti.5li aim I’CI_~., | I .3. '."-i | [15.75l (.0 15.76 {0 [Exercises 665 0.50 aim Clg, and 0.20 atm lift; at this temperature. (a) Use the reaction quotient to determine the direction the reaction must proceed in order to reach equilibrium. (is) Calculate the equilibrium partial pressures at the gases. (C) Wh-‘It effect will increasing the Volume of the system have on the mole fraction oi CI; in the equi— librium mixture? id} The reaction is exollu-rlnic. What effect will increasing the temperature of the system have on the mole fraction of CI: in the equilibrium mixture? An equilibrium mixture of Hz, I3. and I II at 4581‘ con- tains ti.| I2 mol l I), [i.]'12 mo] 13, and iJ.7?5 mol I II in a itlU-L vessel. What are the equilibrium partial pressures when equilibrium is reestablished following the addi— tion of t], IUU mot 0i I'll? Consider the hypothetical reaction My) -i- 2 Iligl : 3 as), for which Kt. -- 0.25 at some temperature. A Lilli. L 1'Ci1tilion Vessel is loaded with lilil mo] of compound C , which is allowed to reach equilibrium. let the vari- able .\' represent the number of inolfL of compound A present at equilibrium. (.1) In terms of .'t', what are the equilibrium concentrations of compounds I! and C? (b) What limits must be placed on the value of .1' so that all concentrations are. positive? (cl By putting the equi— librium concentrations (in terms of .i') into the equiIibriuin~constant expression, derive an equation that can be solved for .1'. id) The equation from part (c) is a cubic equation {one that has the form at" -t- in} i or I if -— it). In general, cubic equations cannot be solved in closed form. | Iowever. you can esti— mate the solution by plotting the cubic equation in the allowecl range of .r that you specified in part ibi. the point at which the cubic equation crosses the I—axis is the solution. (cl I-‘ron'i the plot in part (cl), estimate the equilibrium concentrations of A, It. and C. ll'lttll.‘ You can check the accuracy of your answer by substituting these. concentrations into the eqllilibriulti expressionl At I2titi K, the approximate temperature of automobile exhaust gases (Figure 15.16], K)” for the reaction 2cozi‘n : 2mm) :- this} is about | X iii "3. Assuming that the exhaust gas [total pressure I atm) contains 0.2% CC), 'IZ'ii. ('13:, and 3% 03 by volume, is the system at equilibrium with respect to the abet-e reaction? Based on your conclusion, would the CO concentration in the exhaust be decreased or in- creased by a catalyst that speeds up the reaction above? ‘ Suppose. that you worked at the US. Patent Office and a patent. application came across your desk clail‘ning that a newly developed catalyst was much superior to the Haber catalyst for ammonia synthesis because the cata~ lyst led to much greater equilibrium conversion of N2 and H3 into NH; than the lIaIier catalyst under the so me conditions. What would be your response? 666 Chapter 15 | Chemical liquililnium Integrative Exercises |'i..-'H Consider the following equilibria in aqueous solution: til Nuts) - Aging] ;—' Naimi} Agra} (ii) 3 | Iglli "" 2 All'lmn T" ‘ 31l53"(tir3) + 2 AIL-i} (iii) Xnts) i- 2 I | (my) .——_r auteur} t- rum (a) For each reaction, write the equilii‘Jrium-conslanl ex- pression for K, . (b) Using ll1F(1I'111i1litJll provided in Table Hi. predict \\'hether K is large (Kr 31"» l} or small [K.. 4-1:” 1). Explain vour reasoning. {cl At 25°C the reaetion 01(5) t lemma} ‘—‘ Cd"‘tm}l I ran has K, =' [‘3 X it] 2. If Cd were added to Table 4.5, u-‘ould you expert it to be above or below iron? Explain. 15.79 Silver chloride, AgClEs}, is an insoluble strong elee. lrolyte. (a) Write the equation for the dissolution of Ag( its] in. t [300). ([1] Write the expression for Kr for the reaction in part (a). (Cilitisecl on the tl‘termoehemical data in Appendix C and Le Chatelier’fi principle, predict whether the soluhilit_\_-' of AgCl in HgO increases or ele— creases with increasing temperature. [Itilt The lu'pothelical I'eat‘lioit A -2- H 2‘ C occurs in the [Q Forward direction in a single step. The energy profile of the reaction is shown in the drawing. (a) ls [he forward or reverse reaction faster at equilibrium? [bl Would you expect [he equilibrium in favor reactants or products? (C) In general. how would a catalyst affect the energy profile shown? id] How would a catalyst affect the ratio 3 of the rate constants tor [he forward and reverse reac- r lions? [B] How would you expect the equilibrium con— : slant 0f the reat'tion to change with increasing r temperature? Reaction pathway l'l5.3'll (‘nnsider the equilihl'iur'n A u——" 13, in which lioth the forward and reverse reactions are elementary (single— step) II'ACIIOHS. Assuuu- that the only effect of a catalyst on the reaction is to lower the activation energies of the. lorward and reverse I'eaclious, as shown in Figure l5ft5. Using the Arrhenius equation (Section I43), prove that the equilibrium constant is the same For the catalyzed reaction as For [he uncatal_\-‘7.ed one. [|_5.82] At 25°C the reaction (Q Nl-lil-lfim .2“ VHin + llgfil‘fi'l has Kr, ' It. [20. A Still-l. flask is charged with 0.300 g of pure l'lzf‘iij") at 25°C. Solid Nl"[_;l'|S is then added until there is excess unreaeted solid remaining. [a] What is the initial pressure of I lgSf‘el in the Flask? (bl Why does no reaction occur until Mild-IS is acldeti'.’ (c) What are the partial pressures of Ni ii and I'lZS at equilibrium? .l1.-"i'-'\i 15.84 [15.85] {'0 l'rim't't'lu'r'mu l.- fiquilibrium 2: (Cl) What is the mole fraction of l IJS in the gas 111i,“le at equilibrium? (2] What is [he minimum mass, in grams. of Ni l.;| IS that must be added to the flask m achieve equilibrium? Write the equilibritu‘n—constant expression for the equilibrium (is) t— COZQQ') n—h Ei'i'lllul The table included below sho\vs the relative mole p”. t‘entages of C03“) and COR] at a total p ressu re of 1 mm for several temperatures. Calculate the value of KJl (1' each temperature. ls the reaction exothermic or en- dothermic? Explain. CUE C0 'lbltlperatiire [°C) {mol "fol (moi tiii) 850 (1.23 93.77 950 l .32 518.65 man [1.]? WM 120:.) (lilo 995“ in Section. Hi we defined llie \ apor pressure ol'él liquid in terms of an equilibrium. [at Write the equalion repre- senting theequilibrium between liquid water and water vapor. and [he corresponding expression for is“... tbl By using, data in Appendix ll, give the value of K}. For this reaeliou .il' Rtt‘t'. (c) What is: the \‘alue of Ki. for any liq- llid in equilibrium with its vapor at the normal boiling point of the liquid? Polyvinyl chloride {l’Wfl is one of the most commercial- l_v imporlant polymers ('i'atale [2.4). PVC is made by ad- dition pol_\rn'u.‘rizallott of vinyl chloride (Cgl MCI]. Vinyl chloride is synthesized from ethylene (C21 l4) in a two- Step process involving the following equilihria: Lat-11(5) | Hats) ——‘ Tauelgim C_.II_,CI;_(3) 2' (ill-ladle) + acme) The pl'oL‘luel oi Equilibrium l is |,E-Cllchloroellit‘u‘te, a compound in which one (.'l atom is bonded to each C atom. ta) Draw Lewis structures for Cglltl‘ll and (ill—tail. What are the L.‘ (T tmmi orders in these two Compounds? ([1) Use average bond enthalpies (Tath 3‘4} to estimate the enthalpv changes in the two equilib- ria. (cl 1 low would the yield of Cal-Itch in Equilibrium | varv with temperature and volume? {{1} l [me would the yield of C3] l1('l in l'lt'lllilll'tl'ltllll 2 vary with tempera- ture and volume? [[3] Look up the normal boiling points of l,2-dichloroethane and Vinyl chloride in a source- book, such as the (‘Rt‘ t-iamltmak«Chemistryamt l’lurfiics. Based on those data, propose a reactor defiign {analo- Ieons to Figure IEi.12} that could be used to maximize the amount of Cgl'ljtjl produced hv [IL-tingJ the lwo equilibria. l: [HA EXERCISES I'ln‘r-L‘ t'XL‘TL'iHL‘H nmkv um- ul' th' inh-rwtin- :ilnjm'L-c amilabk- un— linc- in (Nu-Kuy m' this ('mnpuninn \'\"‘*bsil£‘, and Lin your Accel- m'alm' CD. :\u 52-; in 111950 resources; comm-r: in yuur Mi-diui’ak. huh Yuu um Chuner Starling, L'LiliL'L'Ilirdlimn-e fur l'thll‘lillilh in the Chemical Equilibrium .utli\'lt_\-' Hfiji}. (:IJ Wl'ito [he m]uililwimn—cnnstanl L‘XPI'L‘hSlllll l'ul' llu‘ I'vm‘tinn in th‘ Sunulation. {[1] Calculate that mle (if ilil.‘ [.‘qllllibl'lllfii constanl. (Cl 13inch this I'vm'iinn Iiv in tlic righl ur in tin: lL‘I'i? Using tlw vqnilihi'ium L‘onstanl llmi. yuu calculatml in Ihv pt'ux'it'nus qLuMimi for llii.‘ I'L'aciiun in Hui Cl‘IEI‘I‘IlCfll Equi— librium £lL‘ii\'ii_\-‘ (ii-Ll), predict whai the equilibrium mn- t'untmliuns Ul l'L':ICl¢111lH and prudth will lw if you start with mum? M iivlinrgi and l}.[J-i M SUN (liq). L590 ihu simulatiun in L‘l‘IL‘t‘k your mmu'm'. The higrlil‘mim'v of [In vquiiibi‘ium constant? nugmtudv i5 illLlrill'illL't'l in ll'lt' Equilibriun‘l Cfillslalll activity ('l."i..:‘]. St'll‘t'l tlw A u ‘ lii‘L‘dCiiUIi,€Il1L‘lmrr'ymilm‘vvr- ul L‘xPl‘i‘iil'iL‘l‘lll-i with varying Starting Cum'vntrulinns21ml varying equilibrium cum-31.11113. livi'uum‘ I‘i‘iii'li'llil'rl are Id 153M va‘lia lixvi't‘ifiw 667 \'R1:I'L‘tl wth K‘ is \'L‘l'_‘." small. is it l‘t‘hbll‘lt' if! L'nlw'n Way small \‘uiuv for K, hléli'l with only A (no ii), and xlill haw only A <11 uuuilihrium? |-'xp|nin. in lixrl’i‘isu I334 _\'LJll mlvulalml KI. fm' tlu- I'iuu'timi Nil-Jqu fl 2 NUgfxl. (.1) Which ut' the rmctinna in Ihv .quililu'ium Constant i‘tLIliVll)‘ {ill} [weal i'L‘Pl'L‘HL'nlti the L‘qllilibi'ium hr‘lu-m‘cn NEOlQ-q'] and 2 N03“)? (b) UHng llu‘ nimulntinn, L‘Hlt't' th‘ Kl. \‘dlllt‘ from Exor- cist ISIH and Cxpl‘l'il'nt‘l'll Willi \an'ian whirling (uncon- il'aiium vi :‘i-m‘h‘lni and PI'ULth'lF. ("in )‘nu Hl‘ll'l'l starting ('mirm‘iil'alinm Lil I'L‘iit'liilll'fi .md prmiucis "iLlL'll llmi III! vinmgc in L'w'uft'lili'nlimm i5: nlatam'x'ud? Explain Consider ll'll' A ~——‘ I5 and .v .—;?I 215 Functions in tin: Equilibrium Conslanl activity (HR). Asaunw 11ml .-'\ and ii am‘ both gnsc'fi. llmi .-'\ ‘ 15 lh an l’KUllil'l'Hlli' rc- :u‘iinn. and tiinl .»\ :4? I! is an Cnt‘lLJllit‘l'lTlR' ['t‘ilt'lil'll. FUI' 110111 Functions, tililll.‘ th‘ vii-mil lhul thil'li iii thL‘ I'nl inu'inpJ L‘l‘IrIii'gvH would haw: un tlu‘ \'.Ill.|l' (if K. , tl‘Im'nn- t‘t‘l‘lll'alltll'l Ul- 15 (11 l‘RillililJi'lLllll, and 11w I'uh- nr Hu- t'mL'iiun: (‘1)it‘n‘n‘nfim‘l lL‘il'IPI.‘l'dlll['L’, lb) llll'l'l'df-il‘il lH'E'H” blll't', and {c} midilion ofn catalyst. ...
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This note was uploaded on 07/17/2008 for the course CHEM 122 taught by Professor Zellmer during the Summer '07 term at Ohio State.

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ch15homewk_10 - 660 Chapter '15 I' Chemical Equilibrium...

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