practice-midterm1_b-key

practice-midterm1_b-key - KE Name TA Student ID Number “...

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Unformatted text preview: KE \/ Name TA Student ID Number “ LAB Sec. # ; TA: ; Lab day/time: Dr. Toby Allen Spring 2005 CHEMISTRY 2B Midterm I CLOSED BOOK EXAM! write answers HERE No books, notes, or additional scrap paper are permitted. All information required is contained on the exam. Place all work in the space provided. If you require additional space, use the extra sheet of the exam and refer to its page number in your response. A scientific calculator may be used (if it is a programmable calculator, its memory must be cleared before the exam). (1) Read each question carefully. (2) For Parts I and 11, there is no partial credit given and only answers marked on this cover page will be graded. (3) The last 2 pages contain a periodic table and some useful information. You may remove it for easy access. (4) If you finish early, RECHECK YOUR ANSWERS! U.C. Davis is an Honor Institution Possible Points m_/3 Part1 (1- 13) — 3points each Part II (14- 1g— 6 points each Part III (. [fit - 20 points Part III (20) - 20 points Re-grade bonus —- 4 points - Total Score 412 pOintS total H3 m3 Name: T3 Midterm Exam I (Page 2 of 12) Part 1: Multiple Choice, Concepts, (3 points each) Write correct answer on cover sheet — No partial credit 1. (3 pts) A paper cup containing some water will not burn when exposed to flame because: A. the paper was not flammable to begin with. B. the temperature of the water goes up but the cup stays cool. @ the heat capacity of water is large and temperature cannot exceed the boiling point. D. the water cools down the cup because of lower specific heat capacity. E. heat is dissipated to the surrounding air too quickly. 2. (3 pts) A system consists of some dry ice enclosed in a sealed rubber glove. The system is exposed to room temperature and atmospheric pressure during a lecture. Which of the following combinations is correct? A. Work is positive and heat is positive. B. Work is negative and heat is zero. C. Work is positive and heat is negative. @Work is negative and heat is positive. E. .Work is negative and heat is negative. 3. (3 pts) Which of the following describes a colligative property? A. Any property affected by solute concentration. B. A property related to phase changes or osmosis. © A property that is affected by solute concentration but not type of solute. D. A property that is affected by intermolecular interaction strengths. E. A property that is affected by the type of solute but not concentration. 4. (3 pts) The CsCl crystal structure is comprised on a cubic lattice of Chloride ions with Cesium ions occupying cubic holes What are the coordination numbers (CN) and numbers of atoms per unit cell (N) for each ion? A. or: CN=1, N=8; Cs+z CN=8, N=1. B. or: CN=1, N=1; Cs+z CN=8, N=1. c. or: CN=8, N=8; Cs+: CN=8, N=1. (D) or: CN=8, N=1; Cs+z CN=8, N=1. E. c1": CN=6, N=4; Cs+: CN=6, N=4. 5. (3 pts) Which of the following are not likely to form a solution? (structures on data sheet) A. 1—propanol and water. CB; carbon tetrachloride and ethanol. C. hexane and heptane. D. acetone and chloroform. E. carbon disulfide and acetone. Name: TA - Midterm Exam I (Page 3 of 12) 6. (3 pts) Which of the following will have the highest boiling point? A. Pure water. B. A 3.0 molal aqueous solution of nonelectrolyte urea CO(NH2)2. C. A 2.0 molal aqueous solution of strong electrolyte NaOH. D. A 2.0 molal aqueous solution of weak electrolyte acetic acid CH3COOH. (E) A 1.5 molal aqueous solution of strong electrolyte MgClz 7. (3 pts) Which of these statements about a bottle of root beer is false? A. It contains much dissolved C02(g). ® The dissolved gas, sugar and other compounds increases the freezing point above 0°C. C. When heated quickly the gas (and the root beer) are spewed from the bottle. D. When the cap is removed the drop in pressure reduces C02(g) solubility and gas escapes. B. When put inside an ultrasonic cleaner the root beer is shot out and hits the ceiling. 8. (3 pts) Which of the following statements about water is fag? ® Ice at any temperature can be melted by pressure. B. Water can exist as solid, liquid or gas at atmospheric pressure. C. Water has a normal freezing point of 0°C. D. Water molecules interact by dipole-dipole, van der Waals and H-bonding. E. Water has a vapor pressure of 760 torr at 100°C. 9. (3 pts) 2 CO(g) + 02(g) -) 2 C02(g), AHrxn = —283 kJ/mol C02 produced. Which of the following statements about this reaction are true? I: The reaction is endothermic. (3) Work is done on the system by the surroundings. Gil? The enthalpy would be different if solid C02 were formed. IV: The reaction would be assisted by increasing temperature. A. I & III. B. 11 & IV. C. II & III & IV. (E II & 111. E. I&II&III&IV. 10. (3 pts) Two solutions A and B are placed in a closed box and left overnight. The next morning the box is removed and it is observed that solution A has decreased in volume and B has increased in volume. How can this be? A. Solution A has a larger surface area than B. B. The solute in solution A is deliquescent while that in B was not. C. Solutions B was initially at a much higher temperature than A. @ The mole fraction of solute in A was initially less than in B. E. The cleaner accidentally knocked over the box and refilled the solutions carelessly. Name: Tn Midterm Exam I (Page 4 of 12) 11. (3 pts) For a reaction at equilibrium, which of the following could explain the existence of much reactants and little products? I The reaction quotient is large. 11. K is large. Gil?) There was an excess of reactants. GD K is small. V. The forward rate is less than the reverse rate. A. IV. B. 11 and/or 111. ((9 III and/or IV. D. III, IV and/or V. E. 111 and/or V. 12. (3 pts) Which molecule below would you expect the highest boiling point? (E B ‘f‘a CH3CHZCHZCHZCHZCH3 CH3CHZCHZCHCH3 C T343 D THa CH3CHZCHCHZCH3 CH30H2T0H3 CH3 or E) There is no difference because they have the same molecular formula. 13. (3 pts) The equilibrium constant K = [302 MW] [$03][H2] is appropriate for which reaction? A. 802(g) + H20(g) r——‘ 30303) + H2(g) ® SOs(g) + H2(g) : 502(g) + H20(g) C. 503(g) + H2(g) x——“ 502(8) + H200) D- S02(g) + H200) :2 803(g) + H2(g) 13. 2303(8) v“=‘ 2802(g) + 02(g) Name: T fl Midterm Exam I (Page 5 of 12) Part II: Multiple Choice, Short Calculations (6 points each) Write the correct answer on cover sheet — No partial credit All required data can be found on data sheets. 14. (6 pts) Calculate the enthalpy of the following reaction per mole of chlorine gas reacted: C12(g) + H200) 9 2HC1 (g) + V202(g) (Enthalpies on data sheet.) AHW‘ = ZAHECHW?)\ + é AHECOchS) * Alfi[email protected](q)) -— A ego—50(6) ; ZXCLCIZ'SI Mimi) +- O «— O —— (:— zgagm/noi) :— + i0 i '2 k? A) -101.2kJ B -470.4kJ C) 470.4kJ @101.2kJ E) 193.5 kJ 15. (6 pts) Given that K1,=4.6><10'14 for the reaction 2C12(g) + 2H20(g) 9 -4HC1 (g) + 02(g) at 25°C, what is the value of Kc? , ‘ TS ‘ "’5 ‘~ * ’ "k ‘(S‘K' 77 KC;- 95.6%) it; @952ch Lafm/mcI/k 73g 3 = km S .1.9x10'15 B) 1.1x10"° C) l.lx10'12 D) 1.9x10'l7 E) 3.1x10"8 16. (6 pts) Ethanol has a normal boiling point of 78.5 °C and AHO‘,ap = 42.6 kJ/mol. Calculate the vapor pressure at 25.0 °C. . ~ . _ P H Awe:— 01F?) " 4759(7'. '2 77>— 27Z'LY+78‘S = 3>“!'6S”K ,. 10,: lcdm “F _ 4: zogxio3j/mol " L_ _ i 1- 06 3>é71(&lc:lfl\\’ g3lzf,§.j//vbi/K (357%? 29g"\&) 2 / :7 FL: 63‘2"“ :2 (90.73 aha A) latm B) 2.2x10'61atm C) 13.7atm @ 0.073 atm E) 0.77atm. Name: m Midterm Exarn I (Page 6 of 12) l7. (6 pts) If a solution containing 4 moles of A and 6 moles of B boils at 85°C and the vapor pressure of pure A at 85°C is 500 ton, what is the vapor pressure of pure B at 85°C? 79:04. , Xg=0‘é PR, 29, F; ~.— Ovfié—«Saitédr : zoom (firm: Fuel: 7meor/ =7 e}: erg/314*: 960w , 0 .9 0:, F3 3;: 37,066”-.. (7‘ at) 933 torr B) 336 ton C) 260 torr D) 576torr E) 960 torr. 18. (6 pts) Given the following reactions, what is the enthalpy of the reaction X9W+4V ? X9Y AH1 X “’3 ~‘/ 43“! Y->w+2z AH2 .Y A w 1" 22 A112, 2v—>z AH3 ' , , {129-9 44/ -1C>Hl K 4? mm 44/ («+1 rbfia'ZLfl—i} A) AHl—AHz-ZAHg B) AH1+2AH2—2AH3 C) AH1+AH2—AH3 D AH1+AH2+2AH3 @AHfi‘AHz—ZAI'h Name: '73: Midterm Exam I (Page 7 of 12) Part III: Long Answer Show all work - in snace provided— Partial credit All required data can be found on data sheets. [9120 pts total). A: (9 pts) Draw the phase diagram for iodine (not necessarily to scale, but use information on data sheet). L_______abel axes, all single phase regions the fusion sublimation and va or ressure curves, t__he triple point and the critical point. (mph; diayam/ Lmrk QQCL%W l O 1 MS P 760 rm /.C “M (Jrnrk «(A B: (3 pts) Draw the 760mmHg isobar on the above diagram and mark Tg, Tb and Tc on the T— axis C: (8 pts) Draw the corresponding cooling curve for latm, spanning from T down to Tt—IOK. L___a__bel axes and] identifl Ti, Tb and T on the temperature— —axis. (Am HIGHS t max @100 (fit/737‘]. (nfimééicrt \ (PLOT wmmcs 3 sun-(MCI: an act—f INtoflJlCC'? 5661164 '7. loTé Name: ffl Midterm Exam I (Page 8 of 12) ‘20. (20 pts) A lOOmL sample of methanol (CH3OH) liquid is heated at atmospheric pressure from 25°C to its normal boiling point. The sample is heated until it is completely vaporized. A) (12 pts) How much heat is required? mass: elm/x 0~7CijimLK ‘OOML = ’7fo neiarmcgs : not 4— 16.00“?“va -.—. 32°Olr-Zj/flwi n .— mes/”OWMS = 7951;”; = 24,066,,10; (2”qu 2: fix OHS/q? + (ix/l XAT C‘H’lCJ‘kA 1‘ Za‘réémd x 337°0m033/wi + 81", ‘S/Moi/Q: xzvqféggb— (‘00 r: +Cf362‘15’j + 799843 B) (8 pts) What is the change in internal energy of the sample? ALTéflNkTIi/é mat—47% 0N P4415 ‘? £610.15 mrrr. we aw SMY jeNO’LE— voLuMé 0F mr'rm amt/0. 307““ WW AfléoK. {LT .—— r W: ~{“\A\/= 'fif)’ «nfL/ 63'“ kg N - " c “' . 3-(§*6§~o K :- 'Z“%éMol x 93w: Mai/24 k Cf , ’mns: 7— «~693M “Wm” End of Exam Name: TA Midterm Exam I (Page 9 of 12) Extra page — if needed you must refer to this page number. 21 Q ~ (ALT 613N476 ANSk/HL . @Wmm Vmuné\_ vi 3 OH I..- VF ; Q%1' ,2 2.54“ mi r 008256 mam Moi/k x (’273~15+Es}>)k : 6 87+ L. ”WA AV; “1. 6".83 L (gmrkg w: ~Pm4fl/ ‘ - 1m.» gKGL .. ~e<a>+3 bath“) (was 4—— ,. " ’63‘3 x (0’3 x (01325— mzloq ; ~6‘TZO‘S'MZVCL *" -éCzZOfi‘f :: r 6 . C? k: CZmGnkS\ 7) GUS-2ft“, == +l0l57 - 6‘9 L3 (S‘Aflé nasuLT\ ' Name: :2 & Midterm Exam I (Page 10 of 12) Extra page — if needed you must refer to this page number. Name: TA Midterm Exam I (Page 11 of 12) Useful Eguations and Data Sheet Conversions: latm = 760 Torr = 760 man = 101325 Pa = 101.325 kPa = 1.01325 bar 0°C = 273.15K = 32°F 1 cal = 4.184 J Constants: R= 8.3145 J/mol/K NA = 6.022 x 1023 mol" 0.08206 L atm /mol / K d (H20) = 1.00 g/mL cP (H20) = 4.184 J / g ”C AH0f(H20 (1)) = -285.8 kJ/mol AHovap(H20) = 44.0 kJ/mol Kf(H20) = 1.86 K kg/mol Kb(H20) = 0.512 K kg/mol Tb(CH3OH) = 65°C d(CH30H(l)) = 0.79 g/mL AH°vap(CH30H) = 38.0 kJ/mol 2,, (CH3OH(1)) = 81.1 J/mol/°C Iodine: Triple point 114K and 92 mmHg; Critical point 808K and very high pressure (much greater than 1 atm). AH0f(HC1(g)) = -9231 kJ/mol Equations: PV=nRT; w = — PextAV; q = n AH° csp=q/(AT x mass); 2: q / (AT x n) 1n(—1?2—) = 31—1—335- (i — i) ; RV = ianT R R n T. AH 3x” = ZVPAH? (products) — ZVAH? (reactants) Cszgas; PA=XAP°A ATf=-ifoxm; ATb=ibexm KP = Kc (RT)Angas Name: 76 Molecular structures/formulae: Midterm Exam I (Page 12 of 12) ethanol CH3CH20H l-propanol }CH3CH2CH20H 1 11 chloroform carbon Cl/E;C1 tetrachloride Cl/§;C1 hexane CH3CH2CH2CH2CH2CH3 heptane CH3 CH2 CH2 CHZCHZCHZCHS 0 fl carbon S=C=S acetone C disulfide 1131:” \m3 ,‘A Periodic Table of the Elements 1111111 50 :19 93:! La Ca 13119 140.1 1529 1411.2 211 Mn NI C29" . . 51m 5093 59.99 93:10 33 :19 4o 111 42 Sr Y Zr Nb Mo Tc 95.41 87162 911.91 91.22 92.91 95.914 199110u 55 56 11 12 13 14 15 1e 31 011 Cs Ba Lu Hf Ta W Ra Os Ir2 Pb BI Po At Rn 1329 1373 1150 119.5 1999 1939 186.2 190.2 1951 191.0 20015 201.4 207.2 209012091 (219) (2221 101 109 109 110 111 112 Bh HS) Uun Uuu Uub (271) (272) (217) (PHI?) 1550.4 152u0 94 119 90 A1: Pu Cm Bk Cf Es Md No 1221) 23 he 2310 12311 12441 12Nn113'1 (2411 1:241) 1251; 12521 12511 12591 12591 111 15 IIIA VIA 13 14 1?: 1s 11 1e 9 11 12 Si s Cl Ar 5 vms 113 19 2690 23.09 30.91 32.01 3545 399 35 Zn Se Br €9.39 69 12 12.24 1651.92 1991: 1990 53 Rh Cd 811 I 102.9 10: 4 1078 112.4 114. El 118.7 121. 8 .278 128. 9 131. 3 86 :3: gag 11.1 Uuq Er 1H°9 191.3 108"; 11311 101 102 66 Gd By 151 3 15159 152 5 ...
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