{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

chem152_ex1_pkt_A_key - 8 ChFMifile/e/c EXAM LLPSM...

Info iconThis preview shows pages 1–15. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 2
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 4
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 6
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 8
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 10
Background image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 12
Background image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Background image of page 14
Background image of page 15
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: 8 ChFMifile/e/c '- EXAM LLPSM fiacwr® 6cm“) IKE-J CHEMISTRY 152A ' HOUR EXAM I (Version A) Fall '04 ' ' Thursday, October 28, 2004 Name: ________...__,_ TA Section: - :1 Student Number: __ - TA Name: 1 Score (page) 1 (3724') _ j 2 ”a i GOOD LUCK! 3 1512,; 3 SHOW YOUR WORK IN THE SPACE PROVIDED 5 {if ' 1 (possible points = 100 pts) ' g Total __ (fia) I. CONCEPTS AND SHORT ANSWBR: (7'5 pts) ' 1. Indicate which of the following quantities is no; a state function: { _ 4) P v @ v T E H .G 69 2. in the fermula w = - PAV, why theminus (-) sign? . ’- (4) . entry} Ari 4?“ I“? J‘j’éh In (wan-'01.. [d {1):}, a;flfl4 E fij‘c/m/ pad 3. For a liquid, ASEfusion) is larger) than AS(vaporization)_- Why? (4) yak,” “(9,3,3 cgé'd—> [figs/d ,‘5 MM rw/m’ flax-e (”/th c4915: /2)m2-73~:/ 5’ )hc-mror “1% ”9/4”?- 4. For an},r spontaneous process, which of these terms is always positive? (‘0 AS( surroundings) AS(syste_m) ' @ _ 5. Which of the following statements is true(T) or false (F): ( G) ' i, 7" (a) All real processes are irreversible % g g I 1 r 1 g T (b) In an irreversible cydical process, the system returns to its original state, but the universe does not. - F (c) All spontaneous processes increase the disorder of the system 1. 6. In the isothermal, irreversible expansion of a gas, give the sign (7) “+” or “-“ or “0” ) of each of the following quantities: : w q AE AH :38 AS(surr) AG . 3' _<’9 >0 0 o >0 <0 <0 i 71' A gas expands isothermally from 1.0 to 2.5 liters against a constant external (6') pressure P of 1.0 atm. What is w (in Liter-atm)? w=_p11v= ..f/,ai’-)(2.r./,o)ubfi_--/.s’M’~ 97‘... 8. Which of the f.ollowing preperties are intensive? 1’ 5' mass .emperature volume .oncentration energy 9. If 30 mL of water at 280K is mixed with 50 ij of water at 330K, what' is the final (5;) tafifiperature of the mixture? 1103 303:){ggg [email protected](33¢1}= /0‘S"r‘ 206:3UA’ ' Bdwgm'fif— My“ '1“ .2 $HK '15 10.. Consider the following reaction quence: m {C} (a) A —. 28 (b) B —v-C+D (c) E -2_D In terms of the enthalpies of reaction l-I(a), etc, write an expression for the enthalpy of reaction for the reaction A *2C+E AA!» . Mm .. add/4w" Mm ewes”- WQZCV‘W' 61H) ZC-he‘" i i 1 g 11. If a diatomic molecule'spontaneously forms from its atoms {a} - 2 Big) - leg) (a) Predict the signs of - (b) Would this reaction become non-s e0 3 at higher or lower temperature, and why? swim: q/ 413:"? 74’ 024 A 6 = 45/1, "7341.) ‘44:” rm¢alwt 719T: 52”"!"4’43‘ are?” ewes/’1‘: Jean. 12. For the melting of a solid Xls) —- X0), the enthalpy of fusion AH°= 9.2 kf/rnol and (’6) the entropy of fusion A80 = 43.9 J/(K moi). Calculate the melting point ( in_°C) A6“:- 0: A/ya“_7ZI-S_° ,7": 9- ZX/Og/ajzfi/ V3.9 -W,t ' ' “293 2209 - . ' _ - . . —c C. 13. For the same initial conditions (n,P,V\)Ya:—,in?7—?messure, the isothermal expansion (cf) of an ideal gas results in a”, smaller) final volume than does that of an adiabatic expansion. (Inn-1:: e' correct answer) ' 14. A Chemical reaction is determined to have AG°<< 0. Indicate whether the following (4,!) statements are true(T) or false(F): ‘ F (a) the reaction proceeds very rapidly to the right —- as written. F (b) Kleq) = 1.0 T (c) . K(eq)>> 1.0 F (d) At final equilibrium, the reactant concentrations will be much greater than the product concentrations. LMHH.“ _‘._. ,. . ... . .. ...-....-. ._-... _ .. 4.1 . ... -hrrhm.i~r_.m —.. .. ......n..amwaMA-rmum—vazm~u-_.t..- 15. For the chemical reaction A _. B, give the conditions for spontaneity as a function of (q) temperature for each of the following cases: ' (a) 5330 and AH<0 sfmféhrou 6;" o/x’ WM»; (5) AS>O and AH>0 Vméneaa: q?! 434 flies/W‘s: (c) sS<O Hand AHcO 5'flflaA‘Hf-0uf aft/av MM?“ 4 _ (d) AS<0 and AH>O 4w"?! ywém’W-f 41°37 74’7”? W 4‘" w?! 11. QUANTITATIVE: Do- either one of the following (25 pts) 16. Consider the reaction: . 2 POCl3(g) -- 2PC13(g) + 02 (g) {la/#7» A957) (25) ' (a) Determine AGO (kj/mol) for this reaction at standard conditions, using AGf 0 (P003) = -502 kJ/mol AGf 0 (P613) = —270 KI/mol c a ._ o (—9927!) Ar; = EAQODM) 5436:er = 2K-290fi/Z/J'1/2Kfiv2 WWW o (b) If ‘53 for this reaction is 79 J/K, c culate the temperature at which the reaction just becomes spontaneous. ( 5 came? bur) A5”: Aé/‘L 745% M4“: Jami-£15“: ,4;¢,£7+2?8(.229;§3k 4%": 5/9/53“ £6030 : 4/5",- 72350 7‘: Ail SEAL - 29W . AF“ ape/5(7)?” 34’ F341 ét‘CWJ _.S}0%4»/0b5 (A6457) 74v— >4We4m- 7 >23?” J‘— .14.....‘-.;M.._._«. "II—whmun—n-MM-Mdh—SMMHMDWHH. ...... 4. _. —r:(maul—'Alfilmfiimfi'L-Ifldhfiw ' ' www~ll‘wmmmlw.gnfiéam-u , ...muami.» ...:1 17. Stratospheric ozone (O3) is destroyed in the following reaction: flpwé/m J01 4? (’25 ) Now) + Ostg) - N02(g) + 02(3) Calculate AGf 0 and K(eq) for this reaction, given the following: IHHWGWWWWEHHAim-Ir.fiuwun'fit-‘-'-'—. .:..=- 1:.ch (N02) 52 kJ/mol AGf ° (03) = 163 kJ/fnol aGfO (N0) = 87 kJ/mol 46 °= 2’ Aqrww {Aw/mo”) = A 5; Na) 79c: arm) + 4 affadf ”g2 Ar "3% 82%?“ Mam/j 545°: _- /?8AJ .3 0: —~ _ 4.6;: ’4‘; Raga”??? ’9“ 9””Z— R7” k-Pf‘“ :- (9)10 / ~19g/Y/o fad/4w: 3.3291(44‘9 (2993: u a. '5 1 way 719’ K7 WZJmJ/vflrzwf z e . K 29-9? 351-90: 3;» f; 3 If 3': /O '—‘- STGFX/o «www.mr---_-WW.¢MW a... :mmuuz. ¢ . .. .....___.........«..._4.-m_.._. .dummaa. I) A.) {4 points each). Fill in the blanks proirided on the left of each of the following questions, with the letter corresponding to correct ansWer that best describes that question. DO NOT CIRCLE THE LETTER: 1) Which onecfthe following statements is considered to be incorrect or false? P.) A) The change in internal energy, 135', for a process is equal to the amount of heat absorbed at constant volume, qv B) A bomb calorimeter is a device that directly measures 11H of solution at constant pressure 4— M4 in:- una-“4' ”(me C) The change in enthalpy, AH, for a process is equal to the amount of heat absorbed at constant pressure, 9,, D) If qp is negative, then the process is considered to be exothermic E) The boiling of water is an example of an endothermic reaction 2) The statement “the total entropy of a qstern and its surroundings always increases for a spontaneous process" is E A) the third law of thermodynamics B) the law of definite proportions C) the first law of thermodynamics D) the law of conservation of energy E) the second law of thennody'n'amics 3) For which case must a reaction be spontaneous at all temtnres? A A) AH is negative and AS ispositive B) AH = 0 and AS is negative C) AS 5= 0 andAH is positive D) AH is positive and AS is positive E) AH is positive arid AS is negative 4) Which one of the following statements is considered to be Lug regarding the reaction shown below? _Ca__. . CIHSOHU) + 301(3) -+ 2C01(g) + smog) + 137010 A) The enthalpy change would be the same if gaseous water Le. H10(g} was formed as a product B) The gaseous products of the reaction will occqay a larger volume than the 3am reactants C) The reaction will have a negative value for the change in entropy (ASK D? rthereimtioniserir'lotlciermic 3. _~_ 2”,; q E) This reaction is not a combustion reaction at all 5“ ‘3“ ii 5) Which one of the following species will have a standard molar enthalpy of formation value (AH?) of zero (0)? _'D___. . A) ”113(3) B) NHaORQ) C) “(3} D) N203) E) CHAS) 6) The molar heat capacity at constant pressnre (.Cnl for a diatomic gas such as 02 will always be E . A) = 3/23 B) 2— ’11s C) «c “as D)= 5/112 3 E) > ‘mi 7) Which one of the following is considered to be incorrect and false when anideal gas is demanded isothemiallx? Ca . AJAH=0 B)AT=0 C)AS=0 D)q=-—w E)AE= 8) The egnation for the standard enthalpy of formation ofth; (g),_is A) N20 (3) + '01(g) _. N103 (g) B) N205 (g) -+.. N20, (2) + Dag) C) N: (g) _+ 3320:1(3) -+ N20: (2:) 13} Note) + N020}; “" ”201(5) 1E) mo (3) + more) a 142030;) 9} The heat of vaporization of earbdn disulfide [(231) is 26 9 kJErnol Its boiling point is 45l .0 “C The change in entropy for the vaporization of carbon disulficle in J i K: tool Is 3 8 'b . l L A) +0.59"? B) +84.6 ' C) +6637 D) +109 E) +597 £3.14 _ lL‘lw-«llh-tl g+q ,— —. Tr- ”sink-v 155 = FT?"- 10} Calculate the value of 1311' when 25.3 g of Hg is reacted with oxygen, according to the following equation 3 _ 2HgU) + 02(g] -—> 2HgO(5) AH = ~90.3k.l A) —45.4 k] B) —5.73 k] C) —7.36 k] D) —9.3'21d E} ~90.8 k] _ a. 54’ 25.53 H3 KW): a 5 = ~5‘Jslq 11) The specific heat of nickel (Ni) is‘O.4_44 J I g-°C. If 35.0 J of heat are added to a 50.0 g piece of nickel at 22.0 “C, then what is the final temperature. of the nickel? E" . A) 3.8 0C B} 13.2 ”C C) 19.5 °C D) 24.5 “C E) 25.8 “C is: wtcLT 2 Mc— (17.5.”‘1‘10 3&2!) T T: (90.033( 44% faxcj-‘i’ "- 11.n‘c‘b T5,} = 23:33 00:. B) (2 points each). For each of the following reactionsiprocases indicate if the change in entropy is “positive” or “negative” or “equal to zero” by inserting either one of those words in the blanks provided to the left of each reaefionfproeecs. a) w“_94‘“;_‘”____ 11 (g) —> 12(3) b) _ etdhz‘” ____ cmtg) + mice) a Cong) + mice) 6) 1’55““ ' . mixing 1.00 ml of neon (Ne) with 0.25 mol of He at room temperature at) __-_1’:*-_31‘_M_—______ Klaus) —+ 14* (sq) + Brice) e) 33mm CO'Lg) + '11 Oitg) a CO: (33 ln—m— P f) 31-va- so, (g) at 298 K, 5.0 am -—> 30, (g) at 293 1-; 2.0 arm I W at M, II) On the following pages solve each one oi the problems by showing your complete work in em ding any statements or formulas and all the calculation steps leading to the correct answer with the right number of significant figures and the proper units: l} (16 poims) Consufier the following reaction: 2 H201“) —} 2 H10 (0 + 02 (g) Gwen the following data: Com-ound ' H2029 H299) 0m AH“ sz‘mol —188 —286 0 so mm m Calcuiatc thc valucs MAG" in U and the value oflslfnr the above: rtaclion 3125 9C. Given R = 8.3145 JIK-mol. AC1} AH-° -—‘I—A§.' KL 16": L AW 1 [9.9130 * (Dfl -- 11 (435% 7' “H‘- “5:4 ‘35:: :: [it—(o cb+ C1053... [1(H03—E " \zr—Efl—L H haS’ Eli: Mu:— - a? 413* *5 N3 = (”F”- m ‘_ (’45 QC :A—k— =l“ly’ LT/w-‘Q M [m «ELI. L: 7-‘a§$)<lb+° w, = -255 147M K: Mam“ 2} {S pomts). Calculate the. enthalpy for the hydrogenation of C284 shown by the following equation. C2“: (3) + H2 {3) “* C1H4 (3) and making use of the following data. 2H;(g) + 02(3) ‘—> 21-1200} AH“ = ~372kJ 2 C214; (g) + 5 02 (g) —> 4 (202(3) + 21-1100) AH“ = —2600 k] C1H‘ (g) + 302%) -—> ZCOfig) + ZHZOU) AH“ = -1410k1 em = J: (115 — (m) r J—L m KM z 2: _,,‘,,.,3~ (we) 4 54m -'3(13‘- HL—x- 35 L“) 4.}L/o 2 4(1ng t “ 1'76 LAT 3) (20 points). Considet a 1.00 ml 33mph: of a monoatomic gas being subjactcd to the fnllowing two—step [:3 irreversible process: 3 5 CV $11 Ce“ F— Step 1 ' Sup 2 PA24‘003‘I“ Pa=4.00m Pc=l003tm VA = 10.0L M 5 V; = 20.0L 5 Vc = 20.0L Calculate in kiloioules fin: value; of}; q. wmmc combined two-step process. Given that l L-atm = 0.1013 k1- 9R; 4‘- ‘ CMSM ? lea-sir L. LI“; afiwk ELV ._.__ -- (+.wm.>(1o.aL—-Io.g ©(Tf—z" flu" 1 1w MPH: aficzmfi - 3.; a g ((+4-MIX10 L3) “(flap-«Qua %: [E (ml!- kaybag II A? 1 MM" =- @6603: ‘32) '2. ‘ELG‘1‘3”E”‘%%B 2: léfi'ffi. LTi (Conunuation of probicm 3) Step 1 4.00 am pa = 400 atm ‘ PC = 2.00 arm 10,01. 3 Va = ZODL i VC = 20.0 L H H PA Va. C943: '2. ‘- “ma— quu-WL uST— ‘JPWAV 2 95 Pen/.1 P 7): “5v 2 ”cvfir:fl%%(;€- f7; = $3.— (El.oune—~\)(m.;§ - (4d-\(3°S("°i}—§3 L-a-hn Ag: “LEAK *1 /(C-%X(3(%”f:% _ 5' " ”1((111 ”3*(E‘I'Hwfi'm‘ifl: L-m—v 2‘ “-lD-K'E. LT (' M IQ: ,. 2- 4+»ng + o = "Lha-S'L {ng— EWLa -; Lox!) IP3— ._ (0,0115 gag“:- 4.a'§1_ L5“ £1?an = 64:75 — L‘v-D’le! =— 45 Mm ‘—‘— L573 —c,..='ze‘> = 95 ;o_ I. Short Answer (Multiple Choice Section), each question is worth 4 points. 1) When % more Vakm ‘ W‘- NW?) A Entropy always increases ' B Entropy always decreases C Enthalpy always increases D Enthalpy always decreases 2) AH; for an element in its standard state is A zero When T=0K B defined to be zero C determined by the first law D determined by the second law negative 3) In a chemical reaction (such as A g B ) if an increase in the temperature causes the equilibrium to shift to products (is. right) the phenomenon may be described by saying that A + -—~ A Entropy is positive B Entropy is negative A =— 9 fl —— _ . ‘L ‘ .— A _ //(; "Enthalpy is positive i) D 'Enthalpy is negatiVe inmates T WM Slmu' n: 4-: not rs; HT Kv—‘J. F.— fflf/ "' ado-Wm; 4) How many of the following quantities are NOT state functions: 1-1931 Gibbs Free Energy, Internal Energy, Enthalpy, flight, Entropy "~ K A0 B1 @ D3 E4 5) How many of the following quantities are intensive (i.e. not extensive): Heat. work, lntemal Energy, Entropy. Pressure, Temperature, Volume A0 B1 @ Ds \ E4 6) The melting point of tungsten is 3680K and the enthalpy of fusion is 35.2 lemol. The entropy of fusion (in Jf(mol-K)) is: f A 0.01 B 0.043 C 2.4 TL?"— r-—~ A; '-‘- - t €369,9— — r - '34?» t— at I:— J 7) The standard enthalpy and free energy for the reaction: Br1(lig)—) Br2(ga.s)_T_ m—l are AH; :BLU lmo! and AG; = 3k] Inzoi. The boiling temperature of Bromine ‘9?— 1;; is (in K): = 3“” “Hutu A 220. B 270. C 298. (”MD 330. ') E 360. _ - -— 733 o. L 8) When a system is in it's standard state 10) 2.3 moles of an ideal—monoatomic gas undergoes irreversible isochon'c Ab 0-9154— l/ heating from 100K to 250K. The change in entropy (in JIK) of the gas is: ' A 2.3 B 11. C 18. ”635. E 43. 153. 7-“ “CV LA "—2—" 230 3" (-2.3>(%(9-W)> 0» ES : '2 (a :5.- u; Ill) (20 pts) 3.5 moles of a monatomic ideal gas is in a cylinder at equilibrium with a piston imposing 4 atmospheres of pressure at 1000. The gas undergoes two changes. Compute AE, AS. AH“; and w for each of these processes: is) In the first process the gas expands reversibly and isothermaiiy to double its volume. AE=AH=0 (2points) V. V. q=—w=nRTln[ ]=3.5*3.31*373*in(2)=1.52M (4points) AS = HR 1:1[5]: 20.16JKK ( 2 points) 1 Ii.1.b) in a second step the gas is recompressed to its original volume by a single step compression Pm = Pl =4Arm Al’ztfi—Vz=lfi—2I/I=—Vl (4 points) w = —PMAV = RV. = nRT = 3.5 *8.3l * 3T3 210.8kJ q=—w=+l{}.8kJ AE=AH=O (Zpoints) E V I AS=nRin£ ]=—20.16JIK (2p0ints) ||.1.c) What is the net AE, AS, AH,q and w for the two steps summed together? AE=AH=AS=0 (2 points) qflt'l' : —"Vflflf : F3‘3U ( 2 pOintS) ”2) (20 pts) Use the following series of reactions involving 02 burning: Reaction All species are considered to be in the gaseous state unless specified. AH; W) 484 3) Determine the enthalpy of formation of one mole of hydrazine (Nil-14(1)). AH} (KI), and the entropy of formation, AS“ (J I K). (not the absolute entropy) of hydrazine NZHJU). N2 + 2H2 —> NEH4 (i) (2 points) Rxn = (-1)*Rxn3+Rxn2: AH“ : 535 —484 = 51kt)lr (3 points) and AG" = 607 —453 = 1491c] (3 points) fin rm AG” = AH" — T333!” (2 points) EU? LT" [AHD —AG:H]*SI—l49 AS": I'Ifl =_329.JH< (2 points} I r 293 b) Determine the Gibbs free energy for the reaction 2PM3 ——> N2H4 +H2 in order to decide whether NH3 would react with itself to form these products. Rxn = [-1)*Rxn3 + (1)*Rxn1 + (-1!2)*Rxn(2) (6 points) AGE” = (—1)(—607) + (—653) + (—‘E—l)(—458) = 183k.)r (2 points) Not asked for: But the reaction would not go very far, ammonia is stable. ||.3) (20 points) For a particular reaction (of the A :i B type) the following data are known: Temperature( in degrees K) Equilibrium constant(K a) Calculate the standard enthalpy for this reaction free energy for this reaction (A0” ) AH” +AS" R?" R ln[£]:[_wo][i_i] (3 points) K1 R T2 T2 K -Rln[-l] —8.314ln[0'052] —8.314in[0‘052] K wo:__*fiL_=—M__—§LL=£N__4=_50M LCL [1_1] [l_l —3.5-10 r2 :3 335 290 335 290 ( 1point numerical value; 1 point units) b) Calculate the value of the entropy for this reaction —50-lO3 £:anl+AH =1n(8.5)+————=—l8.6 . R RT. 8314* 290 (3 pomts) AS” :—154.HK ( 1point numerical vatue; 1 point units) c) Calculate the temperature at which K=1.0 for this reaction =ln(l)= an=—£+AS RT R AH :AS; T u _- ‘ 3 T=AH = 30—10 :32“: AS" -]34 ( 1point numerical value; 1 point units; -1 ifT is negative.) d) Calculate the standard free energy for this reaction (AGfm) AG” = AH" —TAS" AG" = —50—[298- 10‘3)(—154)k1 = —4.lkJ ( 1point numerical value; 1 point units; 1 point correct T) (2 points) ...
View Full Document

{[ snackBarMessage ]}