{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

'06 Midterm #1

'06 Midterm #1 - CHEM 131 MIDTERM EXAM K Lindenberg Fall...

Info icon This preview shows pages 1–14. Sign up to view the full content.

View Full Document Right Arrow Icon
Image of page 1

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

View Full Document Right Arrow Icon
Image of page 2
Image of page 3

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

View Full Document Right Arrow Icon
Image of page 4
Image of page 5

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

View Full Document Right Arrow Icon
Image of page 6
Image of page 7

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

View Full Document Right Arrow Icon
Image of page 8
Image of page 9

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

View Full Document Right Arrow Icon
Image of page 10
Image of page 11

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

View Full Document Right Arrow Icon
Image of page 12
Image of page 13

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

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

Unformatted text preview: CHEM 131 MIDTERM EXAM K. Lindenberg Fall 2006 NAME W STUDENTID 1. /25 2. /20 3. /20 4. /25 5. /10 6. /5 TOTAL MIDTERM /105 TOTAL NUMBER OF PAGES INCLUDING THIS COVER PAGE: 14. NOTE: Your answers must be Clear to me. Make sure to offset your answer clearly — if it is lost amidst a lot of other stuff I may not find it. If you have more than one answer I won’t know which one you want me to use. NOTE: As announced, this exam is based entirely on your homeworks. After the exam I will point you to the homework problems that appear on the exam. The numbers may have been modified from those on the homeworks in some of the problems. ANOTHER NOTE: Unless told otherwise, you can assume, without further justification, that all gases are ideal. CHEM 131 1. TRUE AND FALSE - 25 points max, -10 points min All of these T/F questions were on your homeworks. I am NOT trying to trip you up or fool you, so I have NOT chosen the really subtle ones. These are ones that you should have clear and firm answers to. Also7 they have been listed in the order in which they appeared on your homeworks. YOU NEED ONLY ANSWER T OR F. Correct choice = 0.5 points, no choice = 0 points, incorrect choice 2 —0.2 points. 2.4a (1) The P — V work in a mechanically reversible process in a closed system always equals —PAV. (2) The infinitesimal P — V work in a mechanically reversible process in a closed system always equals —PdV. (3) For every process, AEsyst = —AES,W. (4) For every cyclic process, the final state of the surroundings is the same as the initial state of the surroundings. (5) AH is defined only for a constant—pressure process. (6) For a constant—volume process in a closed system, AH 2 AU. (7) A thermodynamic process is defined by the final state and the initial state. (8) AT 2 0 for every adiabatic process in a closed system. (9) If neither heat nor matter can enter or leave a system, that system must be isolated. (10) Since a Carnot cycle is a cyclic process, the work done in a Carnot cycle is zero. (11) A change of state from state 1 to state 2 produces a greater increase in entropy when carried out irreversibly than when done reversibly. (12) The heat q for an irreversible change of state from state 1 to state 2 might differ from the heat for the same change of state carried out reversibly. (13) The system’s entropy change for an adiabatic process in a closed system must be zero. (14) For a reversible process in a closed system, dq = TdS. (15) For a closed system, AS can never be negative. lfl 11" in lab we HM In W1 l‘“ H 3.114 ”5.2% 3w? 3.4 la. (16) For an adiabatic process in a closed system7 AS cannot be negative. (17) For a process in an isolated system, AS cannot be negative. (18) For an adiabatic process in a closed system, AS must be zero. (19) For any closed system, equilibrium corresponds to the position of maximum entropy of the system. (20) The entropy of an isolated system can never decrease. (21) For every process in an isolated system, AT : 0. (22) If a closed system undergoes a reversible process for which AV = 0, then the P — V work done on the system in this process must be zero. (23) AS when 1 mol of N2(g) goes irreversibly from 25°C and 10 L to 25°C and 20 L must be the same as AS when 1 mol of N2(g) goes reversibly from 25°C and 10 L to 25°C and 20 L. (24) For a closed system with P — V work only, the cyclic integral f PdV is equal to zero. (25) For a closed system with P — V work only, the cyclic integral f dqm, / T is equal to zero. (26) For a closed system with P — V work only, the cyclic integral f dqm, is equal to zero. (27) The relation AG = AH GITAS is valid for all processes. (28) Always, G = A + PV. (29) The chemical potential ,u, is a state function. (30) it, is an intensive property. (31) p,- in a phase must remain constant if T, P, and at, remain constant in a phase. (32) The chemical potential of benzene in a solution of benzene and toluene must equal the chemical potential of toluene in that solution. (33) The chemical potential of sucrose in a saturated solution of sucrose in water at 300 K and 1 bar must be equal to the molar Gibbs energy of solid sucrose at 300 K and 1 bar. 4 in l” H 7+1 ya H H In in WWW“ 1*“ la lii H l—l,§QC (34) AG is always zero for a reversible process in a closed 145%. 4.0m 43% Mt Lark system capable of P — V work only. (35) The work done by a closed system can exceed the decrease in the system’s internal energy. 36 Gs st + Gsurr is constant for any process. ( y (37) A353,“ + A33”, is positive for every irreversible process. e term 3 an ar state imp 1es t at t e tem erature lS . (38)Th t d d ' 1‘ h h p ' 0°C (39) The term standard state implies that the temperature is 25°C. (40) Doubling the coefficients of a reaction doubles its AH". (41) The reaction N2 + 3H2 —> 2NH3 has 2, V,- = —2. (42) The reaction N2(g) + 3H2(g) —> 2NH3(g) has AH; < AU;. (43) When an exothermic reaction in a closed system with P — V work only is run under isobaric and adiabatic conditions, AH = 0. (44) When a substance is in its thermodynamic standard state, the substance must be at 25°C. (45) G of an element in its stable form and in its standard state at 25°C is taken to be zero. (46) The chemical potential of an ideal gas 1' in an ideal gas mixture at temperature T and partial pressure B- equals the chemical potential of pure gas 1' at temperature T and pressure 13,-. (47) For an ideal gas reaction, K 2, is always dimensionless. (48) For an ideal gas reaction, K109 for the reverse reaction is the reciprocal of K; for the forward reaction. (49) For a particular ideal gas reaction, K2, is a function of temperature but is independent of pressure and of the initial composition of the reaction mixture. (50) For an ideal gas reaction, AH" must be independent of T. f” b1 H ltl‘lldl‘hbblnld It H H l“1 lnH CHEM 131 Moi WM” 2. 20 points total, 4 points each part Consider a perfect gas contained in a cylinder and separated by a frictionless adiabatic piston into two sections, A and B. Section B is in contact with a water bath that maintains it at constant temperature. Initially TA = T3 = 320K, VA = VB = 1.50 L, and n A 2 113 = 1.75 mol. Heat is supplied to Section A and the piston moves to the right reversibly until the final volume of Section B is 1.00 L. Calculate the following. Assume CV,m = 20.0 J K‘1 mol‘l. Also7 R = 8.314 J K‘1 mol‘l. (a) The work done by the gas in Section A. ‘ ’ Vg),_ “£1 __ ”WA ”NB—-8 PAVZ—S “gelgfiv V5)! VEH V .— " ——’(\ RT; ‘0’“ \IB)9’ 3 3 -6,}Smrl>(%-3W X/Kmnrf) (326K) zem % (b) AU for the gas in Section B. CHEM 131 (c) q for the gas in B. ‘h:~w3 Wflob:0 WWI—u!" Ch: ”LQ‘UQ: (d) AU for the gas in A. 6e)zve,»=<’a,.\m mrvs {vi-«4 ~===> {2,122 15%» A150 (LMLALu/u.) fA)\=€&,\ MA 81);: ‘95,); ML :: M7: T2)‘ T—fizl ‘9 T53: @V‘AZRH 1(1,5’)(3_£_> 320K ) 9/4,! 7:; (LS) / f L :5 $55—$91, 7> 175;: mop ADA; “MG/,4“ AT: (\,?-S}nr’0 (20:93/rmr’ K) (4‘10-330)K (e)qf0rthegasinA. AUf-x: H2 *3. AURSIQFM m is; $3 :2 mama} MM l')’ W CHEM 131 3. 20 points total, 10 points each part Data for this problem: CW. = 75.291 J /mol K for water. AH," for melting of ice is 6020 J final. The molecular weight of water is 18 g/mol. (8.) Calculate the change in entropy when 95 g of water at. 0°C is added to 195 g of water at 95°C in an insulated container. mic «n “T: :_(n1C "MOE 51194.14 (11—273 K) :—-|0.gm1r( (TE—348K) Té _,_ (51:13)(2‘*3) +(lo.8)(348) K _..____——————--‘— 523+|018 £531. 33':- ASZmIS Cwol'l'pmag CII’“ all" M222 ($.xznd)(1§,a%1I/mdz)h 1% *- m.£~ar4)(?smlf/mxr) 342 .— 35.? 5/K "" W's—"371: CHEM 131 (b) Repeat the calculation when7 instead, 95 g of ice at 0°C is added to 195 g of water at 95°C in an insulated container. fling DHM 4" ’fllc‘o’M ATT4~ fl’CfJW A7: :_ 0 (same (.4010 mm + (g, ggwt) (15,2011J/m4y4) (7,}273/2) +(ao.2me)('+531€/J’/M MC 71-3422 K) :2. o )4»(I0,8)(?§.2?I){3(3) E 1 4571310020) +(§.?8)C7‘§'2q')0}3 »WW"’”“" K ($119+ 1083051190 1? 2 310 k 310 310 T A5: AH,” +Ifl,g CM‘AT-ni—mm Cgfik {7:312 213 T 349 jMao (€13 A)(éOZLOS/’m't) (3 “MW? 711131“) :5: : M $9,331 osS/L — Isa T/K {— Héf/K + s- .1? W H iii/ CHEM 131 /’M 4. 25 points total 5 point each part For each of the following processes, deduce Whether each of the quantities q, w, AU, AH, AA, and AG is positive zero, or negative. a)Reversible melting of solid benzene at 1 atm and the normal melting point Heat QM KW MW [E] AHzgh 50- W:/PAV,A\/>o ==> IMIsmo/U £0 Whaler] 50 Aug? S0- M: [lam-£15 Au=€r+w ASz‘f/T— so Aprzvo Soiflfléo' WM'W’ “Mr 5°- (b) Reversible melting of ice at 1 atm and 0°C. 10 CHEM 131 (c) Reversible isothermal expansion of a perfect gas. fi»cm§l‘v So lfll—lzol Exiomsim —.=:> 1’2"“) 50‘“ llpxz—TAS:——T9¢_;-ar:vq $0 lflfléol ‘1’ ACZrT—Ag $0 91420 (A940! (d) Adiabatic expansion of a perfect gas into a vacuum (Joule experiment). lW’Ol fldzfiww solAULOl Au: AU +AUOV) =AU+mR£W Bull Ali—.0 W flf;0 .30 lbl—l70i AS >0 (inmggw What‘s, WM) flair-TAS so GEE DC: ”TBS So 11 CHEM 131 )Joule— Thomson adiabatic throttling of a perfect gas L.“ :51 1*“ <3 \ T— m5‘1’m‘)’ AJLaLmLt'C 9" 12 CHEM 131 5. 10 points The reaction N2(g) <—+ 2N(g) has K; ; 3 x 10‘6 at 4000K. A certain gas mixture at 4000 K has partial pressures PM = 650 torr, PN = 3.00 torr, and PHe = 300 torr. Is the mixture in reaction equilibrium? If not, will the amount of N(g) increase or decrease as the system proceeds to equilibrium at 4000 K in a fixed volume? 1 bar = 750 torr, «Ml-“KB Moi. W [email protected] ~13 {um/1A MW ,, 13 W CHEM 131 6. 5 points The Gibbs free energy of a certain gas is given by 1 1 Gm = RTlnp+A+Bp+ §Cp2+§Dp3 Where p is the pressure and A, B, C, and D are constants (independent of T and p). Obtain the equation of state of the gas. ’30 , 9F _ /_. Iv _,,.2:.¢ , v“ 9P. 1' a 9 > 14 ...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern