KEY EXAM 1 - Last Name First Name Lab Sec. # ,' TA: ' Lab...

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Unformatted text preview: Last Name First Name Lab Sec. # ,' TA: ' Lab day/time: Andreas Toupadakis, Ph.D. Winter 2009 Good luck © CHEMISTRY 28 Section C EXAM 1 (circle one) Instructions: CLOSED BOOK EXAM! 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 back of the exam. A scientific calculator may be used (if it is a programmable calculator, its memory must be cleared before the exam). This exam has 10 pages total. (1) Read each question carefully. (2) For Parts I and II, there is no partial credit given and only answers marked on this cover page will be graded. (3) The last page contains 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 Points # 1-10 (3 points each) / 3o # 11-14 (6 points each) / 24 # 15 (6 points) / 06 # 16 (10 points) / 1o # 17 (10 points) / 10 # 18 (10 points) / 10 # 19 (10 points) / 10 Total Score (100) / 100 11-14 fafa/ pomrs: Name Winter 2009 EXAM 1 (Page 2 of 10) Part I: Multiple Choice, Concepts (3 points each) Select the best answer and enter your choice on the cover sheet - No partial credit 1. Choose the CORRECT energy profile for enthalpy and internal energy. ©AT2009WIN E H U U E H E H E U H U T T T T (A) (B) (C) (D) 2. A reaction is taking place in an isolated container, i.e. energy transfer in any form is not possible between the system and its surroundings. Before the reaction starts the reactants are at “X” °C. The products of the particular reaction have higher potential energy than the reactants. When the reaction is complete, the temperature of the products is “Y” °C. ©AT2009WIN A. Y=X B. Y>X C. Y<X D. Y=2X E. none of these 3. What is the formation reaction for table sugar C6H1206? ©AT2009WIN A. 12 C(graphite) + 12 H2(g) + 6 02(9) —> 2 C6H1206(s) B. 6 C(graphite) + 6 H2(9) + 3 02(9) —+ C6H1206(l) C. 6 C(graphite) + 6 H2(9) + 3 02(9) —+ C6H1206(g) D. 6 C(graphite) + 6 H2(9) + 3 02(9) —+ CeH1206(s) E. 6 C(diamond) + 6 H2(g) + 3 02(9) —> 66H1206(s) 4. Which of the following gases will form the liquid state when it is subjected to compression at room temperature and without cooling it? ©ATZOO9WIN A. CH4(TC: 191 K) B. 02 (TC: 155 K) c. N2(Tc= 126 K) D. H2 (Tc = 33 K) E. 502(Tc=431 K) Name EXAM I (Page 3 of 10) 5. Thermal energy of a sysTem is: A. The parT The sysTem's inTernal energy ThaT changes when The sysTem changes iTs composiTion due To a chemical reacTion. B. The parT The sysTem's inTernal energy ThaT changes when The sysTem changes iTs composiTion due To a nuclear reacTion. C. The parT The sysTem's inTernal energy ThaT changes when The sysTem changes iTs phase. D. The parT The sysTem's inTernal energy ThaT changes when The TemperaTure of The sysTem changes. E. none of These answers ©AT2009WIN 6. An aqueous soluTion of NaCl 0.92% m/V is isoTonic wiTh human blood. Consider The following shapes of blood cells and choose The correcT combinaTion of shape and NaCl soluTion concenTraTion ouTside The blood cells. ©AT2009WIN C) (D O X Y Z [NaCl] > 0.92% m/V 9x, [NaCI] = 0.92% m/V 9 y, [NaCl] < 0.92% m/V 9 z [NaCl] < 0.92% m/V 9x, [NaCl] = 0.92% m/V 9 v, [NaCl] > 0.92% m/V 9 z [NaCl] = 0.92% m/V 9x, [NaCl] < 0.92% m/V 9 v, [NaCI]'> 0.92% m/V 9 2 [NaCl] > 0.92% m/V 9x, [NaCl] < 0.92% m/V 9 v, [NaCl] = 0.92% m/V 9 2 [NaCl] < 0.92% m/V 9x, [NaCl] > 0.92% m/V 9 v, [NaCl] = 0.92% m/V 9 z mcow> 7. Five soluTions are made by dissolving equal numbers of moles of each of The following compounds below in 200 g of disTilled H20. Choose The compound whose soluTion will have The lowesT boiling poinT. ©AT2009WIN A|C|3 CH4 HN02 NaCl NH3 WCQW> 8. Consider a very diluTe aqueous soluTion of The sTrong elecTrolyTe Na2504. For This elecTrolyTe in waTer aT very low concenTraTions The van'T Hoff facTor will be: ©AT2009WIN Name EXAM I (Page 4 of 10) 9. Water is boiling in two pots, one is covered and the other one is not covered and you are ready to make tea. Unfortunately the phone rings and you need to leave the house. You turn off the stove and go. All other factors being equal, when you come back you will find the pot which was not covered to have cooler water becau3e: A. during evaporation the least energetic water molecules are escaping and thus the temperature will decrease even faster. _ B. during evaporation the most energetic water molecules are escaping and thus the temperature will decrease even faster. the water molecules during evaporation are rotating, vibrating and translating. the water molecules during evaporation require more space. none of the above ©AT2009WIN mg.“ 10. Consider the following compounds: ©ATZOO9WIN n—Butane Isobutane n-hexane n-Pentane Neopentane Choose the correct order for the boiling points. n—Hexane > Isobutane > n-Butane > n-Pentane, and n-Pentane > Neopentane A. B. Isobutane > n-Pentane > n—Butane > n-Hexane, and n-Pentane > Neopentane C. n-Hexane > n-Butane > n—Pentane > Isobutane, and n—Pentane > Neopentane D. n—Hexane > n-Pentane > n—Butane > Isobutane, and” n-Pentane > Neopentane E. n-Hexane > n-Pentane > n—Butane > Isobutane, and Neopentane > n-Pentane Name EXAM I (Page 5 of 10) Part II: Multiple Choice, Short Calculations (6 points each) Select the best answer and enter your choice on the cover sheet - No partial credit 11. Consider the following reaction: ©AT2009WIN C3H8(g) + 5 02(9) —> 3 602(9) + 4 H20(9) For this reaction it is AH = —2043 K! and AU = -2045 kJ. Calculate “w” for this reaction. 3. 4203310 Hzosrp'v AHtoo tPexAV c: -2kJ ‘ D. OkJ pethovx§tum+ ’ Peyav ‘: E. none of the above n» w: AU~ 5le r.» w: (-9.qu karC—ioua Ml 12. What would be the osmotic pressure at 37°C of an aqueous solution containing 2.00 g of glucose 66H1206 (molar mass = 180.18) per 500 ml of solution? ©AT2009WIN A. 0.57atm :1 ' 4’ : fi ’ B. 0.63m 71’ {\AQT /r_, (175% 31 all, k, c. 0.45 atm L Mo-éowucy D. 0.34a’rm .‘ _ E. 0.880Tm Q: 0.082, LOhM‘ “Awe ‘k l m (9085': r 1003 : 0.0ll\ ‘vno€e§ guauv. ‘80- 3\w0(" V:SOO \ML‘Z’O.§OL) M: O°OIHWV€ O.€O L Tr 160.012, W(o.081\/o¥wvm%V/><3lO/m Ti- Name EXAM I (Page 6 of 10) 13. The vapor pressure of pure waTer aT 83°C is 400.6 mm Hg. You are making Tea by using 230.0 g of pure waTer and 5.0 g of sugar 66H1206 (molar mass = 180.18). WhaT will be The waTer vapor pressure of your Tea aT 83°C? Assume ThaT The effecT of The Tea componenTs on vapor pressure is very small. ©ATZOO9WIN A. 401 mm Hg 0 B. 397 mm Hg t 0 “a .: . 5 c. 402 mm Hg A g3 C > “er ><\-\1o PHw D. 398 mm Hg . E. 400mm Hg XHLO : Vlmo \fluwl V\<03.\ who : m/MM. : 130.0 O/l8.o?. awe" :11.1C meg mo, we?) : 5.02) /r80.l8 came” : 007,8 wwées Wow. 0Xon : 11.46/(0018 +\Z.¥6) toque P§c6u -: Cqug x HOO.6 wwRB @ 14. Consider below The general chemical equaTion and The corresponding heaTs of formaTion for each of The reacTanTs and producTs. ©AT2009WIN 3 A(g) + 2 EU) a 4 6(5) + 6 0(9) AH°f (kJ/mol) -4o.oo +3.00 +9o.oo -25.oo CalcuIaTe AH° for The reacTion represenTed by The above general chemical equaTion. . 324k 0 ° ~ ea . 3. 456 kg ARV : 2"“ 5H1: (PVOM " in All; (veec‘vomig~\ C. 289 kJ D. 163kJ QH9(:[‘ AH" ‘ , ° ’ E. 184kJ L” ea) *GXMW (0)1 _ [g*xA\—\;(A\ +113“: (3) : [L‘quQooMcGzaool] "L3C‘Li0.00\ TlCTKOO) 3 : 360.00 ’ l’soTO—C- 120.o+6.00\ ': 1\0.0«/C~ \\L\‘,OO\ : 30-0 i (like gzu (43 Name EXAM I (Page 7 of 10) 15. Consider the energy transfers below between a system “A” and a system “B”. Based on the definitions we gave for heat and work answer for each example if the energy was Transferred as heat or work. ©AT2009WIN _w_ 1. The temperature outside your car is 30 degrees below freezing, but the sun (A) heats up the seat (B) of your car. _q_ 2. Your cell phone's temperature is -10 °C. You put your cell phone (A) on the car seat (B) in such a way that the sun cannot reach it and the cell phone becomes warm. __ 3. Water (A) in a cup being microwaved in a microwave oven (B) gets warm. w __ 4. Water (A) in a pan sitting on an electric stove which is connected to an electrical outlet (B) becomes warm. w __ 5. Water (A) in a pan sitting on an electric stove (B) becomes warm. q __ 6. You (A) inflate the tire of your bike and the air (B) in the pump becomes warm. w __ 7. Your hands (A) get warm because they are facing a fire (B). w __ 8. Your hands (A) get warm because you are in a room (B) in which there is a fire place. But your hands do‘not face the fireplace. q __ 9. Your hands (A) get warm by you (B) by rubbing them against each other. w __ 10. Your hands (A) get warm by holding a hot cup (B) of tea. q _ 11. The tires (A) of your car after a long trip on a very cold road (B) become warm. w __ 12. A hot tea (A) becomes cold in a cup (B). q __ 13. A hammer's head (A) becomes warm after being used to hit nails for a long time by you (B). w 14. A hammer's metal head (A) becomes warm while being held by you (B). q Name EXAM I (Page 8 of 10) Part III: Long Answer Please show all work for calculations - Partial credit may be given (10 points each) 16. Draw the phase diagram of a substance if you know the following information about it: (a) its triple point is 20°C and 0.75 atm. (b) its normal melting point is 25°C and (c) its normal boiling point is 200°C. Hint: You do not need to draw to scale. For ful/ cred/'7‘; label the axes correctly, draw the phase-boundary lines with the correct slope and indicate the areas of, solid, liquid and gas by placing the symbols 3, l, and g in the correct areas. Place a dashed line parallel to the horizontal axis at the position of 1 atm, correctly in relation to the triple point. ©AT2009WIN 17. Consider the following information: ©AT2009WIN 2 A(g) + 8(9) 9 6(9) + D(s) AH1° = (x +2y) kJ 2 D(s) 9 3 C(g) AH2° = (4x +6y) kJ If you know that “x” is a negative number predict if the reaction represented by the general chemical equation below is exothermic or endothermic. 6 A(g) + 3 8(9) -> 5 D(s) For credit show all your work clearly. an +33 -—->zc +30 DH:-:3><+6y 3c ——~>2\3 AH: 24”,“ 6A +7393 —e 50 bliso:(%x+67)tC“LiX-Cy)*3‘X‘ o ‘O.____. m X 7r» ~ Name EXAM I (Page 9 of 10) 18. Silver crysTallizes in The face-cenTered cubic crysTal sysTem. CalculaTe The fracTion of The volume of your silver ring ThaT is noT occupied by iTs silver aToms, i.e. calculaTe The fracTion of The volume of your silver ring ThaT is empTy space. For full crediT show all sTeps of your work. ©ATZOO9WIN 4:6; h—aL’ cal-own {3th (NM (6(6. HR: LE Voeuwe occUpl‘ed by clout/i5 i‘Vi HW€ UVh’r Cef6: —, Ll‘x 9/), no? : lG/g was .3 Vogzwe of uvn’r (9(6“: L 19. You warm up a quanTiTy of waTer in a cup on your elecTric sTove by adding To H 2 J of energy. NexT you Take The cup of waTer and you place iT wiThin an elecTric microwave. You add To The waTer addiTionally 1 J of energy. NexT you leT The waTer cool down and by doing so iT looses 3 J of energy. CalculaTe The change of HS inTernal energy and draw an energy level diagram indicaTing clearly The Three energy Transfers by using arrows. Use The correcT symbols and signs for each Type of energy Transfer. ©AT2009WIN lge S‘lcp q: *1] U chl §lep W : +1.] gvd Clep Q‘1’Z‘] DUZL‘Lcfl +(:w\ :(ivax-yhflifi: 0—; DU :0 M UT :U-C U: >Ufi Name EXAM I (Page 10 of 10) Periodic Table I 11 111111794 .‘4 1.1 6.941 11 Na Mg 1 Be 911121331 12 5 6 7 8 If) B C N O 1 N1, 1&811 12.610? 14,006?“ 15.999: 3998403 101797 I3_ I4 15 ‘ If: I? 13 A1 S] P S Cl A: 22.939770 4.5111521 _ _ _ _ _ 26.98MB; 2311855 30.973761 31066 355.452? 3919:! 19 M311 21 22 23 24 V 27 ‘ 30 35 [30' 1\ L :1 SC '1 1 V (31' n 1 e ’o 11 Zn , K fi‘klflllil 41.955911} 41M? 5119415 51.9961 5433 ‘ 55.8215 53.913331] 58.19934 61.51115 6539 _ ' t 1 37 91511 ’39 ~90 41 42 43 M 45 46 4? 48 49 ’50 51 L 52 53 Rb hr Y Zr Nb 0 F “ Ru 1 , Pd ~ g C 111 Sn Sb 6 I 85.401111 37.113! 88.905115 91224 92. ' B 95.94 CW} 101.07 “12.90550 “£12 [07.8632 112.41] I141", 113.710 121.1160 127,60 [.5 55 . ‘ 5? “1'2 ‘7‘] 'H 75 N 77 7‘ 79 m 11 32 33 1M t. . La 111' To V e ()5 1r 1 AL Hg Pb 131 P0 1311545 117.327 13319055 133149 150.9479 181.“ 186.11)? 193.11 192111 195.078 1%.96655 u“ 117 811 $9 104 105 106 107 108 109 "0 “I ll! 1‘ I“ 1121 1‘10 R1 Db 1311 s 131.11 {211;} (2271 (21.1} {202) ('21. }_ (2521 __(_2165) 1 _ __ _ A Some useful equations: a 1' gr)“ E‘s? “ ~41 125% :3 SM“ :90 a :51“- git“ C E n—x 2R ._- L 4.12 : L.21/2 4R : L_31/2 °/o (m/m) of A = (mass of A / fofal mass of mixture) - 100 ATf = — i - kf- molality ATb = i - kb - molality Molality = nsolute / kg of solvent PA I XA in vapor . Ptoml PA = XA in solution I PoA q=m~CSp-AT q=n-AH° XA=nA/(nA+nB) P7 AHVCI) 1n—'~= ’ i—l— T(K)=t(°C)+273 R R T1 T2 AU=q+w 7t=M-R-T AHO m z 2 [n1 (AHt~°)1 ] products - 2 [n1 (AH 1°)1 ] reactants Some useful data: R = 8.314 J / (K - mol) = 0.0821 L - atm / (K - mol) 100 cm =1010 A 1 nm :109 m d (H20). = 1.00 g / mL AHvap (H20) = 40.7 kJ/mol csp (H20) = 4.184 J / g °C Pwater (100°C) = 760 torr = 1 atm = 760 mm Hg = 101,325 Pa 1 gallon (gal) = 3.785412 L NA = 6.022 X 1023 atoms / mol 1 g = 6.022 X 1023 amu 1 1b = 453.6 g ...
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This note was uploaded on 10/23/2009 for the course CHE CHE 2C taught by Professor Nasiri during the Spring '07 term at UC Davis.

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KEY EXAM 1 - Last Name First Name Lab Sec. # ,' TA: ' Lab...

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