Land exam 1 S99 key

Land exam 1 S99 key - Name TA Lab Section Number Dr Land...

Info iconThis preview shows pages 1–8. 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
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Name TA Lab Section Number Dr. Land Spring 1999 CHEMISTRY 2B Midterm I Instructions: CLOSED BOOK EXAM No books or notes allowed. All information required is contained on the exam. Place all work in space provided. If you require additional space, use the back of the exam. ( 1) Read each question carefully. (2) There is no partial credit for problems in Part I. (3) Show work in Part 11. Credit will be given only for work shown. (4) The last page contains potentially useful info and a periodic table. You may remove this for easy access. (5) Graded exams will be returned in discussion sections next week. i _ _ 5. 45 _ — — Total Score (250) If you finish early, RECHECK YOUR ANSWERS UC Davis is an Honor Institution Key 2 Part 1: Multiple Choice - N0 Partial Credit 1. (10 pts) At 0°C the enthalpy of melting of water is 6.0 kJ - mol". The enthalpy change when 36 g of water freezes is +35 54.03 r 1,521: 2 ml C._~6.0k.l d. +6.0kJ e. OkJ H10(9)';Afl01£)5AH¢ : "léto a—> 5 AH: ~40 W/m, x g Mo/ 2. (10 pts) The standard enthalpy of formation of benzene, C6H6(l), is +49.0 kJ‘mol" and of acetylene, C2H2(g), is +2267 kJ - mol". What is the reaction enthalpy for formation of 1 mol of benzene from acetylene? I Alb/U01 ’1 2/1 {/rw€~> 4- 5)! 21/4; [Anti a. +177.7 k] b. -177.7 kJ -631.1kJ 3 £21101 3 Céfié AH: [2*(+49)1~ [zxfimafl : ~45/,/ e. +49.0 k] 3. (15 pts) What are the number of atoms per unit cell and the coordination number (CN) for a face centered cubic lattice? a. 8 atoms; CN = 12 b. 2 atoms; CN 2 8 c. 2 atoms; CN 2 12 d. 1 atom; CN = 6 4 atoms; CN = 12 4. (15 pts) Calculate AU for a system that absorbs 325 U of heat and v as 65 kJ of ork done on the system. (? +390 kJ A (A) . —260 kJ : .,L c. -390 kJ M g (1. +260 k! e. Not enough information to calculate. g : .}. 32 9 to: M5 Kex/ 5. (10 pts) The boiling point of Br2 is higher than Cl2 because of . hydrogen bonding. K 7i London forces. / c. dipole—dipole forces. )4 0/1 " /0 4}» d. ionic forces. e. all of the above. 6. (10 pts) Which of the following liquids has the greatest surface tension? a. methyl ether, CH3OCH3 b. chloroform, H3CCl c. Br2(1) .b ,CH éwflltlezrane 6 6 H- [jaiwflm ’ i 7. (15 pts) The lattice enthalpy of AgF is 971 kJ - mol‘l and the enthalpy of solution is 22 kJ - mol". Estimate the enthalpy of hydration of AgF. a. -993 kJ - mol"_1 + - @3993k13r-rfii [13 F5) ~47 Ag (g) ’r % F [3) All: All: w C. + m0' A; ms) [~32 450x?) +~ F143) AH: AHSOIA t +22 A2+Z33 4 F‘Y‘j) H“) 129* (47') + F747,) All: MAY = —- 9:11 + 0151 : A W7 8. (15 pts) Calculate the number of moles of oxygen in a 40 L aquarium of water at saturation. The partial pressure of oxygen is 0.2 atm and Henry's Law constant is 0.0013 M - mm1 for oxygen at 20°C. .01 moles m . 8.0 moles ' a. n ‘ a I c. 2.6x10‘4 moles 5 “ is P - I 00/3 / K (D:- d. 5.2x10'2 moles L '61 {In e. 3x10'4 moles : 3310420419" L. - ‘ ol , 7‘0 L94 gag/04 111/ : Let/*1 M K6 \/ 9. (15 pts) Calculate the individual ion hydration enthalpy for the Ca2+ cation [the reaction Ca2+(g) ——> Ca2+(aq)] from the following thermochemical equations: Ca2+(g) + 2C1‘(g) ——> Ca2+(aq) + 2C1—(aq) AH = —2337 kJ/mol @ H+(g) + Cl’(g) —> H+(aq) + cr(aq) AH = —1470 kJ/mol H+(g) —> H+(aq) AH = —1130 kJ/mol A ~897 kJ/mol B +654 kJ/mol c. +41kJ/mol CD ' «2* @ + R4 C?) —2300 kJ/mol @ —1657 kJ/mol "22 593‘ ~ 26/ 4 $0) + 2(—// 50) = ' ME? 10. (10 pts) Which of the following explains why N aCl dissolves readily in water with AHsoln = + 4 kJ/mol? The increase in disorder on breaking up the solid overcomes the endothermicity and order in the solvent. 0. The solvation of the ions induces some order into the water solvent. d. Solids always dissolve in water. e. Both energy and matter disperse in the process. The positive enthalpy of solution follows the natural tendency for energy to disperse. 11. (10 Pts) Which of the following is NOT a property of network solids: a. Very hard. b. High melting points. Held together by ionic bonds. . Variable electrical conductivity. e. ALL of the above describe network solids. Part II: Calculations. Credit given only for work shown. Key 5 12. (20 pts) Draw the phase diagram for water in the space below. Clearly mark (a) the triple point, (b) the critical point, (c) the regions of the various phases and (d) the normal boiling point. 13. (25 pts) Calculate the heat evolved when 28.8 grams of water (molecular mass 18.0) at 50°C is cooled to —50°C. The molar heat capacities of water and ice are 75.3 J.K'1°mol'1 and 37.7 J.K'1-m01‘1, respectively, and AHqu = 6010 J.mol-1. +50 #6th €1/o/V/6fl2 +/gjé5é 2“; >< ’M’ : um»; My Afl=zr a) M *«50 x 29:5 :-goa2i b) /.饗~éO/0 : ‘94/4' C) /’6“‘9'O 7‘ 3%? 2” 30/5 1W : #5, 45¢: U /\/€/ 6 14. (20 pts) A piece of metal of mass 25.0 g at 100°C is placed in a calorimeter containing 65 g of water at 21 .0°C. The final temperature of the mixture is 25°C. If the specific heat capacity of water is 4.18 J'K"°g'l, what is the specific heat capacity of the metal? Assume all heat lost by the metal is absorbed by the water. . 299 mo? I44 X Cap )6 ATM“, 2 "‘ Mior’v; Cipj/jzo x A 7—le g xC lack/*Q54oo :* 2’: ' a ‘ 2; 9/ ) 69371 4,78% 7kg; 521) é 41/2 4 3 (57mm: 9’” * :2 0.55.9; 15. (25 pts) The vapor pressure of water at room temperature is 3.68 x 10‘2 atm. What is the enthalpy of vaporization of water? $1022qu : g/JZx/éjv‘m: fl 7' 5 27g K (25%) P : [calm 7:2 r p: 3,2104 4'49“ “6-2 K'Ma/ 2.16%): fig 4; Key 16. (25 pts) Calculate the reaction enthalpy for the combustion of propane, C3H8(g); C3H3(g) + 502(g) ‘3’ 3C02(g) + 41—1200) from the data: 2H2(g) + 02(g) —> 2H20(1) AH° = —572 k] (1) C(s) + 02(g) —> C02(g) AH" = -394 U (2) 3C(s) + 4H2(g) —> C3H8(g) AH“ = -106 k] (3) -[x (3) + 396(2) + 52*“) :; 65%; “y %%% Aflrl/pé 8 Potentially Useful Information: (You may remove this page for ease of access.) cp=q/AT S=kH°P cspzq/(AT-m) AU=Q+W Inf; =flm i_i P1 R T1 T2 AH=AU+PAV=q (constant P) P2 AH,,, 1 1 1n _ =4 ___ AH=Hfina1-Hinma1 P: R T1 T2 — O O _1. —l AHE.‘n = ZnAH?(products) - ZnAH?(reactants) R _ 831451 L kPa K “101 R = 8.31451 J°K“1-m01—1 R = 62.3639 LOT orrOK—10m01‘1 R = 8.20578xlO'2 L-atm-K—lomol—1 Key At # Symbol 1&8 Mol.Wt. eletroneg 4 0 Li B e B C N 6.941 9.012 10.81 12.01 14.01 . . . 0.98 1.57 2.04 2.55 3.04 . . 11 12 14 15 16 Na M g Si P S 22.99 24.31 28.09 30.97 32.06 . . 0.93 1.31 1.90 2.19 2.58 3.16 - 19 20 26 27 33 34 35 36 K Ca ' Fe C 0 Ge A s S e Br Kr 39.10 40.08 44.96 47190 50194 52.00 54.94 55.85 58.93 72.59 74.92 78.96 79.90 83.80 0.82 1.00 1.36 1.54 1.63 1.66 1.55 1.83 1.88 2.01 2.18 2.55 2.96 — 37 38 39 40 41 42 43 44 45 50 1 52 53 54 Rb Sr Y Zr Nb M0 Tc Ru Rh g I Xe 85.47 87.62 88.91 91.22 92.91 95.94 (98) 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3 0.82 0.95 1.22 1.33 1.6 2.16 1.9 2.2 2.28 2.20 1.93 1.69 1.78 1.96 2.05 2.1 2.66 - 55 56 71 72 73 74 75 76 77 78 79 80 81 82 83 Cs Ba Lu Hf Ta W Re Os Ir Pt Au Hg T1 Pb Bi 132.9 137.3 175.0 178.5 180.9 183.9 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 . . . . . . 2.33 2.02 0.79 0.89 2.2 2.20 2.28 150.4 1.17 ...
View Full Document

This test prep was uploaded on 04/05/2008 for the course CHE 002B taught by Professor Land during the Winter '08 term at UC Davis.

Page1 / 8

Land exam 1 S99 key - Name TA Lab Section Number Dr Land...

This preview shows document pages 1 - 8. Sign up to view the full document.

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