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# another practice exam - cfnsmsrnv 152A HOUR EXAM I(Version...

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Unformatted text preview: cfnsmsrnv 152A - HOUR EXAM I (Version B) FALL '06 Thursday. October 26, 2006 Name: TA Section: StudentiNumber: TA Name: = - Score 1 . - 2 GOOD EUCKI . 3 5 . Total . (x1100) I. COjNCEPTS AND SHORT ANSWER: Answer all questions (subtotal = 48 pts) 1. @F)-For a real, polyatomic gases. Cp = Cv + R For such gases why is Op > (5!2)R ? _. - ' . I maria) - Ll :PDMQH‘DMIC. motqculcs mve t mount diagram - o’r Mac? C _ um? women s “brat-W“; ant-hop cm drum VP 0"“ 99 uﬁ-hM raisins W W' M 3‘18 2. I Consider an ideal gas at 25 0C in a 1.0 liter bulb connected to an evacuated volume of 4.0 liters byga closed valve. Now open the valve, letting the gas expand isothermally into the larger volume. Forthis expansion, give the sign of: q w AE AH AS .AG one so,AE=AH=-O o 0 o O + - (a Put-:0 sOJ-wr-o x _ - 335%“) ‘3‘" 13"” v AG<0 toe Aer-AH —TAS A§>0 since Asaﬂﬂn 3?; - O - (+3 -_ 3. Which of the following statements is true (1') or false (F): " (a) All real processes are reversible F H LSE' (b) in an reversible cyclical process. the s tem returns to its original state. but 3 .: ' the universe does not. H L8 5 (c) All spontaneous processes increase the disorder of the universe mu E 4. If 70 mL of water at 275 K is mixed with 30 mL of water at 375 K, what is the ﬁnal temperature T (in degrees K) of the mixture? Note: water has density = 1 glmL, and has speciﬁc heat = 4.18 Jl'(OC g) 5 (leg/mMQ-IWXTF—mh ‘3om4'9x’mQL‘l-lm'ﬁi-cIT9415) I ; . T+= 3057C :9 ./ 5 Consider the following reaction sequence: (1)2A ~98 L} (2) e ..., 20 + o (3) E —> D In tetrns of the enthalpies of the individual reactions (Ht‘l), etc). write an expression for the enthalpy of the following net reaction: 2A —) 20 + E ' a A a 73 H03 3 ,B’ a 2c. + )25 H3 Mm ..~ Mm album wares e.' Consider the gas-phase reaction 02 (g) ‘5 20(9) Predict the sign 01' AH° and AS" for this reaction? Under what conditions of temperature (much higher. much lower) would the reverse reactionioowr spontaneously? 3 AH‘DO Wﬂb‘nﬁ ag’iﬁdglac [40nd- ASDPO inmqsihj 4:},- Qp moms op .8qg ~2th v.5 21+ +uws 7. At what temperature does bromine boil (P= 1 atm) ? Bram “'9 Brz(g) The enthalpy of vaporization is AH°= 29.0 kJﬂnole. and the entrapy change is AS" = 8?.0 .mK mole} 5 Ae°=mhms°=o ~ “A manta . I; T= 4'7; = smut/ma = i_333“-| j- 8. For the chemical reaction A -§ B, give the temperature conditions for spontaneity for each of the following cases (Le. spontaneous at all T, at no T, T high or T low) ' (a) (LS-<0 and AH <0 ION Rm? . L! (b) AS>0 and AH <0 ant amps (c) AS<0 and AH so no Rh”? (d)AS>0 and AH >0 high amp}, I J. Version B -(.I . 12. .x' ' . Chemistry 152C- ' Page 3 9. The-equilibrium position of an endothermic reaction will shift toward -reectants} with increasing temperature while for an exothermic reaction the equilibnum will shift toward the (products Circle correct response. 10. Foréthe following values of AG". give the corresponding values for the equilibrium constant K_ (K=1, or K >1, or K <1) - . AG" = 0, K A '2 2) AG" < 0, K1? ' .- AG" > c, K 51,? 11. In Boltzman‘s formula for entropy ( S = klnn ), what does 0' represent? Why do more simpler molecules have smaller values of standard entropy 8° ? . - S]. g #09 micmm correspcnm “to given S’CG'W Ll OHM gleam. toothpasihm . mereﬂ simmer moiecwies - how; WV posg‘bu’ ' mﬁhoml Q Vitowthonqb moﬁms @) “SS (inner mime-tu’ch ‘4‘st- ‘hen the system is at ullibrium. .. 0+ awn-imam 75m” =- Astra Asa...” o 3 \$0 Agaui‘f: *Agsrls i 9 Version 13 0/ a . /'t31emistﬁy 152C ' Page 4 ll. QUANTITATIVE: Do all four (4) of the following (subtotal = 52 pts) 1. The heat capacity at constant pressure-of co2 is On = 38.25 .mK mole). Ii 80.0 grams ' of CO its-cooled from 175 °C to 55 °C at a constant pressure of 5.00 atm. calculate q, w. AE . . 2 , . . _ and AH for this process. 303w: .‘LheDl-l- __.., [Elgmolcs 1 Hui-(13 4T3: 55—i?5= ”30 A“ *%= recs AT :6-91'81 3%.161—1203 = «3 mute =~ LU {-1321]; AV ': L1- 5m)(—3,550L\{ \0‘33) 7 18.3 ‘g r: AE%CB-tu.) —: *g-BHLT 4; LQHLE' "=- .2. When 1.00 liter of 0.50 M Ba(N03)z at 25.0 °C is mixed with 1.00 liter of 0.50 M Nazso.‘ at 25.0 to in a calorimeter, a white solid Base; forms and the temperature increases to 28.5 °C.js The heat capacity of the solution is 4.1801(“0 g). (Neglect the heat capacity of the calorimeter, and assume that the solution has a density of 1.0 glmL) Calculate the enthalpy change ism“ for this reaction per mole of BaSO4 formed. head-- 5319va :mCAT .. _ mass = I IOOL+1.DOL— = 2L gent-[ﬂ '-‘ 7.0003 .QéT a 310.5 535.0 =1,5°C- awcy trig/\$00.90 = [363% huuc mm Mm mm = - 135”“- V :- -ia%\io\$ . AH‘ pt’mokt 1L£t6m : ,QSOEOImo" ' 7’ ” QSLT/woe Version B /. a j . . _ 'Chcnﬁsn-Ey 152C Page 5 . 3 Calculate AH°rxn for the following reaction: 4NH3(9) + 702(9) -> 4 N02 (9) + 6H20(|) The AH“; values (in kJi'mole) are: . NH3(g) N02_(g) H20 (1) - - 43 +36 - 275 Apr gwuas imam =E!(5w‘)~!LoLm6ﬂ [LN ”33 +1103] - 45cm — ( W73. 4. Consider the following reaction: : Fezosis) + 3H2 (g) _, 2Fe(s}+3H0(g) Assuming that AH° and AS“ do not depend on temperature calculate the temperature at which K=1. 00 for this reaction. The standard enthalpies of- formation and standard entrcjpies are: i . i 0.: ‘e K: ’-' AH°(keroIe) 8°(J!(K mole) AG O M n " ~T S Fezose) -334 +85 0 A H- H3 A ' Fie(s) (0) +24 ' T 9-- H2 (9) (0) +137 As a H' 20(9) -235 - +175 ' i'.‘" 2314!": CacoHst 33613— [- 33L! 1 am] 12‘1 lei/moi: _ ’35 [3(th Hum] [85 + 30370- W J/Kmole, Wad-r3100” : w’t‘SK Version B ...
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