practice_midterm1_f_key

practice_midterm1_f_key - ' / Name < E Student ID Number...

Info iconThis preview shows pages 1–12. Sign up to view the full content.

View Full Document Right Arrow Icon
Background image of page 1

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

View Full DocumentRight Arrow Icon
Background image of page 2
Background image of page 3

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

View Full DocumentRight Arrow Icon
Background image of page 4
Background image of page 5

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

View Full DocumentRight Arrow Icon
Background image of page 6
Background image of page 7

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

View Full DocumentRight Arrow Icon
Background image of page 8
Background image of page 9

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

View Full DocumentRight Arrow Icon
Background image of page 10
Background image of page 11

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

View Full DocumentRight Arrow Icon
Background image of page 12
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ' / Name < E Student ID Number LAB Sec. # _; TA: Dr. Bryan Enderle CHEMISTRY 2B (Section A) Exam I 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). (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 / ‘\ 1‘ ; Lab day/time: Winter 2005 Multiple Choice 13-19 total pts: Name: Exam I (Page 2 of 12) Part 1: Multiple Choice, Concepts (3 points each) Select the best answer and enter your choice on the cover sheet — No partial credit 1. (3 pts) Which of the following statements is (are) true? nthalpy is a state function. (b) A chemist takes the surroundings point of view when determining the sign for work or heat. (c) The heat of reaction and change in enthalpy can always be used interchangeably. ((31) Your Chem. 2B instructor’s last name is Augustine. (e) At least two of the above statements are true. 2. (3 pts) Which one of the following is the strongest intermolecular force experienced by the Noble gases? an der Waals or London forces I ) Dipole—dipole interactions (c) hydrogen bonding ((1) Polar covalent bonds (6) Ion—ion 3. (3 pts) The resistance of a liquid to an increase in its surface area is called? . capillary action © urface tension (0) vapor pressure (d) viscosity (6) none of these 4. (3 pts) Properties of liquids lie properties of a solid than to properties of a gas. (Note: this problem has no choice (c), (d), or (e) — you have a 50/50 chance.) . farther from loser to Name: Exam I (Page 3 of 12) 5. (3 pts) Which of the following is likely to be a gas at room temperature? (a) sodium sulfide (b) C8H18 jazalcium fluoride \l (d) iatomic nitrogen ooh} Loter v\ Qorgejtf é» \owv‘ 9? (e) water 6. (3 pts) Which of the following compounds has the highest boiling point? (a) CH4 (b) 02 (c) CH3-O—CH3 Ha-OH H \OOlAA j (e) He 7. (3 pts) Which statement regarding water is true? (This one is tricky. . .think about it) (a) Energy must be given off in order to break down the crystal lattice of ice to a liquid. (b) Hydrogen bonds are stronger than covalent bonds. (c Liquid water is less dense than solid water. (Cl) ater has a dipole. (e) Only covalent bonds are broken when ice melts Name: Exam I (Page 4 of 12) 8. (3 pts) The elements of group 5A, the nitrogen family, form compounds with hydrogen having the boiling points listed below: SbH3 —17°C, AsH3 —55°C, PH3 —87°C, NH3 —33°C The first three elements in the list illustrate a trend here the boiling point decreases as the mass decreases; however, ammonia (NH3) d es not follow the trend because of (a) dipole—dipole attraction \/\&3 H - \00 “A ( \Aj (b) metallic bonding \ @hydrogen bonding ""5 \9 ’VQXMK ((1)) Yan er VZaals (London) forces KKKQ Ckeé _ CW e 10nlC on in g m $8 H and 9. (3 pts) Which one of the following statements about solid Cu (face—centered cubic unit cell) is incorrect? (a) The packing layers are ABCABC. .. There are 2 atoms per unit cell. g {:C(_ :3 (Elm (c) The coordination number of Cu is 12 U L’ (d) The solid has a cubic-closed packing structure (e) The length of the face diagonal is four times the Cu radius. 10. (3 pts) The triple point of iodine is at 90 Torr and 115°C. This means that liquid 12 (a) is more dense than I2(s). (b) cannot exist above 115°C. (0) cannot exist at 1 atmospheric pressure. @cannot have a vapor pressure less than 90 Torr. (e) can exist at a pressure of 10 Torr. Name: Exam I (Page 5 of 12) 11. (3 pts) C2H50H(l) + 302(g) 9 2 C02(g) + 3 H200), AH = -1.37 x 103 kJ For the combustion of ethyl alcohol as described in the above equation, which of the following is true? I. The reaction is exothermic ’K 0 II. The enthalpy change would be different if gaseous water were produced. bk) III. The reaction, when canied out in the atmosphere, does no work and work is not done on it. IV. The products of the reaction occupy a larger volume than the reactants. @. II (b) I, II, III (c) I, III, IV ((1) III, IV (6) onlyI 12. (3 pts) Which of the following are state functions? (a) work, heat b) work, heat, enthalpy, internal energy @nthalpy, internal energy ((1) work, heat, enthalpy (e) heat, enthalpy, internal energy 13. (3 pts) The vapor pressure of water above 40 mL of liquid water in a 100 mL container is 23.8 Torr at 25°C. What is the vapor pressure of the water if the volume of the container is changed to 50 mL? (a) about 30 Torr (b) about 15 Torr I . (U \l \u @23.8Torr "’ ‘1'? W re LW [ o M (d) 47.6 Torr (e) 11.9 Torr Name: Exam I (Page 6 of 12) Part 11: Multiple Choice, Short Calculations (6 points each) Select the best answer and enter your choice on the cover sheet — No partial credit 14. (6 pts) A bomb calorimeter has a heat capacity of 2.47 kJ/°C. When a 0.105 g sample of ethylene (C2H4) was burned in this calorimeter, the temperature increased by 2.14°C. Calculate the energy of combustion for one mole of ethylene. (a) -5.29kJ r “A ‘ €ch * as?” ' _ . (b) 503 kJ Club)“ > (5ch : QAT: (Q57 tJ/YDQQ \4 0L) 3211:1213 ka I ‘2 “£35143 (6) Noneo tea ove )(iiiéggfl)<0‘mghfly ,2 l0 K3 ‘ lmo\ 15. (6 pts) When 0.157 mol NH3 is reacted with excess HCl, 6.91 kJ of energy is released as heat. What is AH for this reaction per mole of NH3 consumed? (a) —22.7 k] 6 ‘ k3 b —1.08 k] —44.0kJ -/‘“ Gigi Moi ) -22.7 k] (6) None of the above l6. (6 pts) Consider the following numbered processes: 3.139 2D x L43 AH for the process A -) 2C +E is (a) AHl + AHZ + AH3 AH] + AHZ C AHl + AHZ — AH3 H1 '1' 2AH2 — AH3 (6) None of the above Name: Exam I (Page 7 of 12) 17. (6 pts) Using the information below, calculate AHf° for C2H50H (l) C2H50H(l) +fpg(g) 92C02(g) +3H20(l), AH0 = -1367 kl AHfO (C02(g)) = -393.5 kJ/mol AHf° (H20(1)) = —286 kJ/mol -278 kJ/mol<_.,.— ARK) 2.5“: LQLRXO R} + QAH‘.‘ ((01) (b) 688 kJ/mol ‘\‘ A (RIO (c) -3.01x 103 kJ/mol (d) —688 kJ/mol (6) None of the above 18. (6 pts) Suppose that a battery drives an electric motor in an aquarium pump, and we consider the battery plus the motor as the system. During a certain period, the system does 555 kJ of work on the pump and releases 124 kJ of heat into the surroundings. What is the change in internal energy of the system? (a) 431kJ All: 3+ xi) 7‘ ~— VLA‘ “ff? @431kJ —,: -619pj 679kJ (d) 679 k] (e) None of the above 19. (6 pts) Estimate the enthalpy of vaporization of carbon tetrachloride given that at 25°C and 58°C its vapor pressure is 107 and 405 Torr, respectively. Assume that the enthalpy of vaporization is constant over these ranges of interest. (a) 486 J/mol Q)“ (b) 48.6 kJ/mol E“ 2 139, %?>\ c) 142 kJ/mol GEWS 33.1 kJ/mol (e) None of the above M ‘-\_.....J—_ Name: Exam I (Page 8 of 12) Part III: Long Answer (20 points each) Please show all work for calculations — Partial credit may be given 20. (20 pts) Use the following steps to determine a mystery element found in an unknowa sample at the scene of a crime. (a) (4 points) Analyzing the mystery sample by XRD, a reflection was observed at an angle of 35.0”. The X-rays were a wavelength of 2.0 A. Assuming n = 2, find the spacing between atomic planes of the unknown sample. T\ I"? twe- ‘ Ql L) : CilC'l-c-lx) fl Wk @- , S M G) (b) (8 points) From part (a), the crystallographer was able to determine the sample has a bodycentered cubic packing structure and an atomic radius of 1.40 A. Find the . . 3 volume per unit cell of the unknown sample m cm . Q liar jsz r31 ‘ I “\r ._ g I . E \i : .: (MESH -- ‘ (‘3) -?3 ., l (9%- s “s3 @ \I .3 3 ‘XKQfiq‘i-s Cmim Name: Exam I (Page 9 of 12) 20. (continued) (0) (6 points) After further analysis, the density of the unknown sample was determined to be 9.4 g/cm3. Find the atomic mass of the element in the unknown sample assuming the sample is composed of only one element. alzfl’l a “m:d\l \K W 2 L13 Q‘s/'WwDCS .‘l'Xi Q in _: r) . x (d) (2 points) What is the most likely candidate for the mystery element? Name: Exam I (Page 10 of 12) 21. (12 pts) One mol of a liquid is vaporized at its boiling point, 65°C and 1.00 atm. AHmp for the liquid is 43.8 lemol at 65°C. (a) (6 points) Calculate work. ml >1 9P1N :— J-bm QT 69 ‘ w -~- m (\mx‘j'kemig 3mg (6? i QW-Qllafiy W) :*9\8.\Qi:— avgfljg’fl @ (b) (6 points) Calculate internal ener l—\\ Q3 )5“: fl I: '1” UJ " 9 Wijl/ELLQ Name: Exam I (Page 11 of 12) 22. (14 pts) (a) (7 points) A swimming pool contains 2.0 x 104 L of water. How much energy in k] is required to raise the temperature of the water fmm 200°C to 250°C? (b) (7 points) You decide to use TNT (an explosive) to heat the pool. How many grams of TNT do you need? TNT has a chemical formula of C7H5N306. o . k3 [5% {TNT} : Me\ _ 3‘ fl fl L ‘1: r 2C6: O :7 CEEWSJS: nka (WM) (4.1 xtogfil‘é j Name: Exam I (Page 12 of 12) Conversions: 1 atm = 760 Torr 1 gal = 3.785 L 2.54 cm = 1.00 in = 101,325 Pa 11b = 453.6 g 1 cal: 4.184 I Constants: R=8.3145]/m01K RH=2.179x10'18J c = 2.9979 x 108 m/ s h = 6.626 x 10‘34 J s g = 9.81 m/ 5 NA = 6.022 x 1023 atoms / mo] d (H20) = 1.00 g / cm3 Cp (H20) = 4.184 J / g °C AH° (TNT) = 1066.1 kJ/mol Equations: AU=q+w AH=AU+PAV nl=2dsin6 P2 AIivap 1 1 . . . ln— = — — — q = nAH = meAT , where AH 1s m units ofJ/mol 0r kJ/mol. P. R T. T2 ,‘A Periodic Table of the Elements VIE; +1. I 1m .54 .13: .131 1:1 1151 v1.11 - 3 4 5 a 7 9 9 10 Ne 0.941 9.012 10.01 12.01 14.01 16.00 19.00 20.19 11 12 13 14 1 N Mg AI 31 P _ 5 10 17 13 S Cl Ar '1 ' . . , 3 . 3 . 5,1 :49. r 22 99 2431 “'8 NE 2909 097 207 3 15 95 5 10 11 12 4 VB 113 2’93 19 20 21 22 23 24 25 25 27 29 29 :10 31 32 33 34 35 36 K Ca Sc T1 V Cr Mn Fe Co NI Cu Zn Ga Ge As Se Br Kr 39.10 40.09 44.90 47.97 50.94 52.00 55.05 59.99 58.69 99.55 95.99 139.72 72.94 74.92 79.90 79.90 9350 V18 qu r—Vlllfifi 37 30 39 40 41 42 43 44 45 4e 47 49 49 50 51 52 53 54 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te X 85.47 07.52 90.91 91.22 92.91 95.94 (99) 101.1 102.9 100.4 107.9 112.4 114.8 110.7 121.0 127.0 131.3 71 77 79 79 80 94 St: L A | 126.9 55 513 81 8.5 | At e ' 72 73 74 75 79 92 92 “ Cs Ba u Hf Ta W Re 03 lr Pt u Hg T Pb BI Po Rn 132.9 137.3 175.0 170.5 150.9 199.9 199.2 190.2 102.2 195.1 197.0 2130.6 204.4 207.2 200.0 12091 1210) 12221 103 104 105 100 107 109 109 110 111 112 114 Uun Uuu Uub Uuq 1222.) 12201 12921 12011 12021 12001 (204;. 121391 12001 1271) 1272) 12771 12.99) 138.9 140.1 140.9 144.2 [145) 150.4 152.0 157.3 158.9 102.5 134.9 1137.3 168.9 173.0 100 101 102 ('22?) 232.0 231.0 238.0 (237) (244‘) (243) (247) (24 71 (251) (252) (257) (258 1 (2591 ...
View Full Document

This note was uploaded on 10/03/2010 for the course CHE 547456 taught by Professor Hello during the Spring '09 term at UC Davis.

Page1 / 12

practice_midterm1_f_key - ' / Name < E Student ID Number...

This preview shows document pages 1 - 12. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online