Practice Exam 3 - 0. Graphite is thermodynamicaiiy iess...

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Unformatted text preview: 0. Graphite is thermodynamicaiiy iess stabie that diamond under standard conditions. \f/ (Wine "3-"; 33. 1. Which statement would be the best interpretation of the First Law of Thermodynamics? If 1. The total amount of energy in the universe is increasing. The total amount of entropy in the universe is increasing. V he total amount of energy in the universe is constant. . The total amount of matter in the universe is constant. 2. thalpy (ii) is best defined by which of the foliowing statements? . the capacity of a system to influence the entropy of its surroundings \/ 2. pressure—volume work 3. a measure of a system‘s energetic degeneracy 4. none of these describe enthalpy 3. ater changing from a solid to a liquid is an endothermic change. . an eXOthermic change. 3. Neither an exothermic or an endothermic change 3.2. Heat flow is considered positive when Wiows ut of) a system; work is 0 considered positive when work is done (by a system. out of; by @into; on 3. out of; on 4. into; by 4. Definition: state functions ___ An extensive state function's value is spend on/independent of the amount of a given substance. An intensive state function's va ue is (dependent onof) the amount of a given substance. 1. dependent on, dependent on independent of, independent of dependent on, independent of 4. independent of, dependent on 5. What is the enthalpy change for AH°fC(s,graphite)? 1. —1300 kJ/mol e 2. 31kJ/mol §S~) bK-lr ‘3 O. 717 kJ/moi ‘ kJ/mol . ~S75 kJ/moi 6. Consider the following specific heats: copper, 0.384 J/g-°C; iead, 0.159 J/g-°C; water,4.183/g-°C; glass, 0.502 J/g-OC. If the sameamount of heat is added to identical masses of each of these substances, which substance attains the highest temperature? ( ume that they all have the same initial temperature.) iead 2.. water 3. glass 4. copper 7.1. You set up a bomb calorimetry experiment using 1 liter of water as your heat sink and combusting a 4.409 9 sample of propane (C3H3).‘If the initial and final temperature are 24.90 °C and 77.96 00 respectiveiy, what is the approximate moiar enthaipy of combustion of ethene? {Assume the calorimeter itself absorbs no heat. Assume the density of water is 1 9-mL" ) 1. 422.0 kJ- |-1 7‘ a , 2. —222, 000 kT-OmoI—l A g 7 mooéq'lgqfi cm 24 @142; 3. —22.20 k} - moi—1 i-fff @422, 200 kJ - mo|“i Rifle X \o’HM 2, 220 k] - mo|——1 7.2. A 0.10 9 piece of chocolate cake is combusted with oxygen in a bomb caiorimeter. The temperature of 4,000 g of H20 in the calorimeter is raised by 0.32 K. (The specific heat of the water is 1.0 cai/g-K and the heat of vaporization of water is 540 cal/g.) What is AE for the combustion of chocolate cake? Assume no heat is absorbed by the calorimeter. 1. W460 kcai/g L 771 2. —S32 kcai/g . l 3. ~13.3 kcai/ 12.8 kcaié . "3900 kca g at .\ 8. Calculate the standard reaction enthalpy for the reaction of calcite with hydlochioric acid: CaC03(s) + 2HC|(aq) —+ CaC|2(aq) + H2003) + C0203) The standard enthalpies of formation are: for CaC12(aq) : ~877.1 kJ/mol; K \ for H2002) : —285.83 kJ/moi;,4 \ for C02(g) : “393.51 kJ/moi; fi'\ for CaCO3(s) : —1206.9 kJ/mol; y; s.\ and for i-lCI(aq) : —167.16 kJ/moi. K .r’z 1. “72.7 kE/moi .2. —163 lei/moi 4. (3c) \/ 3. ~3e.2 ki/moi N02 +éfi ’? N O f 94 Z M983 kJ/moi ‘ - @432 kJ/mol M a 3' HZ"? . ~116 kJ/rnol . figfifii 7. —215 kJ/mol We + ’2. 9. Calculation: Hess’s Law and combined reaction entham oz a? M Jr 0 Calculate the standard reaction enthaipy for the reaction: N 5102(9)» Noig) + 0(9) Using: 02(9) a 20(9) [ii-1° = +4934 kJ/mol 3/2 02(0) “r 03(9) Ail" = +1425? kJ/mol NO(g) + 03(9) —> N02(g) + 02(9) AH° a —200.0 kJ/rnol 1. +592 k3/mol v r” 2. +555 kJ/mol +307 kJ/moi . +355 kJ/moi 5. +192 kE/rnoi 10.1. How much internai energy would be associated with the rotational motion of 1 mole of we... iii... 2. 1/2 RT " ‘ '~ ' , t. @0910" WW 3. 3/2 RT 4. 2 RT 10.2. What would be the total vibrational energy of .0833 moles of cetane (C15H34), assuming cetane is nowiinear? 2 RT K e1 E 5 Va RT . 22/, "E 11. What energy change is associated with the reaction to obtain 1.00 moie of H2? The balanced equation is: : @w P. ~ . 2 H20(g) —> 2 H2(9) + 02(9) 3 0/ ‘- O and the relevant bond energies are: ~ . ‘ ' ‘ O :30 Hui-l : 436 kJ/moi; H—O : 467 kJ/mol; /° ’39 2 H’tl 4’ mar—mm; o=o : 498 kJ/mol. H ""\ tr +425 10 I} 249 to Art. r ;, fist; 2<ev>~z<eg 3&5) *2 20+ >t CO 05 " —498 k] 6. M436 kJ 12.1. 1.95 mol of an ideal gas at 300 K and 3.00 atm expands from 16 L to 28 L. and a final pressure of 1.20 atm in two steps: (1) the gas is cooied at constant volume untii its pressure has fallen to 1.20 atm, and (2) it is heated and allowed to expand against a constant pressure of 1.20 atm untii its volume reaches 28 1.. Which of the foilowing is CORRECT? w '; v-— An 1. w = -4.57 id for the overall process _6.03 id for the overall process W ‘- W P ’ U, u»... “24.57 id for (1) and w 2 M1.46 k] for (2) O for the overal? process a for (1) and w = ~1.46 so. for (2) w 1 H ' lt? L716” [(05 N 12.2. 0.500 mole of N2(g) reacts with 1.50 moies H2(g) to produce NH3(g): ‘ N203) + 3H2(g) -> 2NH3(9) If this reaction is carried out in a system against a constant 0.75 atm pressure (§.e., a ) at 0 °C, caiculate the magnitude of the P V work. \/ Zara‘s“ Wome- fewest—7g) 3. 22.7 J 4. 22.4 x 103 J 2 (LT 53. 4.54 x 103.1 13. Which of the following are not forms of internal energy? 1. motion of molecuies v kinetic energy / @heat . potential energy \/ 3. chemical bonds ‘/ 14. Which of the following statements concerning calorimetry is/are true? I) Bomb calorimeters hold the voiume of the system constant. / II) The calorimeter itseif does not absorb heat. x III) AH = q in a bomb calorimeter. X 1. I, II @I only C 3. II only _ g 4. I, II, III \l AE ‘* i OMQM’ ‘0] (9% cl; 5. I, III / 6. II, III 7. III oniy 15. A system did 150 kJ of work and its internai energy increased by 60 kJ. How much en did the system gain or lose as heat? he system gained 60 k3 of energy as heat. The system gained 90 k] of energy as heat. A E ’5: system gained 210 k] of energy as heat. 4. The system lost 90 id of energy as heat. 5. The systemlost 210 id of energy as heat. é a 2-: pl gfi 16.1. For the four chemical reactions I) 302(9) .. 203(g))( ‘/ II) 2H20(g) .. 2H2(g) + 02(g) III) H20(g) m. H209) x IV) 2H20(£) + 02(9) .2. ZHZOZOE) X which one(s) is/are likeiy to exhibit a positive AS? 1. Al! have a positive AS. 2. I, III and IV oniy . 3. I and II only . III and IV only @1 only M? When Angasctiori is large and positive AS for the reaction is likely to be small) and /negative). iarge, positive 2. large, negative 3. smali, positive _4. small, negative 17. Which of the foilowing would have the largest ab ute entropy? /' 2(gil/ 2. N2(s) V 3. N2(aq) (nitrogen dissolved in water) 4. N203) 18. Calculate the standard entropy of fusion of ethanol at its melting point 159 K. The standard molar enthalpy of fusion of ethanol at its melting point is 5.02 k3 - moi—1. 1. —5.02 k3 - K_1'moi”1 2. ~44.o J - K: - mo]: . statue “as o :- s, 02 r 6764’s) +5.02 so - K‘l - moi“1 (xv/19.1. Which of the following statements is FALSE? 1/ s The total amount of energy and matter in the Universe is constant. ' “J reaking chemical bonds is an endothermic processx V 3’ . t is more efficient to use a primary energy source than a secondary energy source. \/ . ‘ he entropy of the system is always increasing. i/ Energy is conserved in chemicai reactions. W X / . Heat given off to the surroundings is negative in sign. 4. AV , AS, and AH are examples of changes in thermodynamic state functionsA/ / 5. Work done on the system is positive in sign. \/ Q \ 20. The law states that a substance that is perfectly crystaline at 0 K has an entropy of zero. This law is called E/ 1. None of these / 2. the first law of thermodynamics. U @the third law of thermodynamics. 4. the second law of thermodynamics. 5. the zeroth iaw of thermodynamics. 21. In terms of absolute entropy, which of the foliowin is/are true? 1) W has both a real and a theoretical vaiue. II) The Boltzmann constant can be used when calculating S for molar quantities. / III) W for 1 mole of CO is greater than W for 3. mole of 02. 1/ 1. IE}: only 2. I and III II and III ' @’ w w :1 l Stet. W r 2 6. I only 7. II and III 22. Which of the following systems would likely have the greatest res+daa4 entropy at If absolute zero? 10 1. 10 BHzF moiecuies U) 1 3 ‘ ?}g f . 20 CCi4 molecules w t 'w M I / I é 9 CHCl3 molecules w 3&9 ~ 1?, 4. 100 BF3 molecules w v \ 23. What is the positional entropy at absolute zero for two moles of CF3Cl? I 1.11.53/K W % \IW 2. 5.73/K I (a, A \/ 3-2355. S : Elm/M the [\i/ @233/K \QV/ 24.1. What is the ASSN when a balloon filled with 8 grams of hydrogen is combusted at 8 °C? The heat of combustion for a mole of H2 is 242 kJ/mol. ,1. 121000 i/K Jase/:33 S »« AHS‘AS 4. #121000 J K "m , 5. ~3o.25 J/K L: sow H a; W T W as) ~8— awms 4, w NW 444 J/K 4- Ar r 30.25 J/K W‘ W ) b/ 8. ~3444 J/K L 24.2. A system releases 3456 3 into its surroundings which are at 125 °C. By how much does this increase the entropy of the surroundings? / 138.24 J/K 3% $9 \/ 8.68 J/K M .5 .11.60 J/K 3‘13 4. this would decrease the entropy of the surroundings 25. For the vaporization of ethanol, AHvap m 38.56 kJ/mol and [Swap = 109.7 J/mol - K. What is the boiling point of ethanol? ‘ o : 365% wt 406v) 26. Your roommate left 150 g of dry ice out on the counter last night and all of it sublimated. Given that AH = 393.5 k3-m0F1 and AS = 2.023 kJ-mol'l-K"1for dry ice sublimating and that the temperature in the room was 25 °C, by how much in totai has has _ your roommate increased the entropy of the universe? r‘ 1. -O.198 k344i": M 4/ A S C :02 2. 0 k3«i<“1 uw-V *“ 5-155 5W" o 9 “ya. 3. 0.105 kJ-K': 2 DZ Bars 3 LEEW " . 0.303 kJ~K' ‘1": , “ * ' .48 kJ-K': 3 Jr W gig, 6. 6.89 kJ-K“ , ... 7. we we Z-°“-""5."’5) 1‘ w“ e 322.». M 2‘38 27. Which of the foliowing statements is always true? 7 1. If the number of moles of gas does not change in a chemicai reaction, then 05" m 0. X reaction for which AS", is positive is spontaneous. \/ '1‘ If Lil-i" and AS" are both positive, then AG" will decrease when the temperature inases. 11 1; q x 4. An exothermic reaction is spo taneous. - 28.1. What ha ens to CuO 5 with resect to its eiements when the temperature is raised? . Unabie to determine w r (a- 2e?) _ 28. . A reaction for which AH is negative and AS is negative f uld become spontaneous at low temperatures. / hit AT JV 2. is spontaneous at any temperature. ‘ 3. could become spontaneous at high temperatures. 4. is not spontaneous at any temperature. 29. The standard free energy of formation of C520) is 65.3 kJ-moi”1. This means that at 298 K . CSzG) will not spontaneously form (3(5) + 2 8(5). MCSzfl) is thermodynamically stable. No catalyst can be found to decompose C828) into its elements. $20!) is thermodynamically unstable. has a negative entropy. 30.1. Assuming that AH°r and A8°r are independent of temperature, what is the cutoff temperature at which the reaction below is spontaneous? 1. 635 K an 61% 456 2. 390 K 3. 573 K ' 7'1 ‘7 ‘6 £76- 25e> ,' pontaneous at all temperatures ...
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This note was uploaded on 03/24/2010 for the course CH 301 taught by Professor Fakhreddine/lyon during the Fall '07 term at University of Texas at Austin.

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Practice Exam 3 - 0. Graphite is thermodynamicaiiy iess...

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