key_mid2 - -1- 14A2W02-2 Baur CHEMISTRY 14A LECTURE SECTION...

Info iconThis preview shows pages 1–5. 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
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: -1- 14A2W02-2 Baur CHEMISTRY 14A LECTURE SECTION 2 WINTER QUARTER, 2002 Second idterm Examination Friday, March 1, 2002 Name fwra a TA: (check one) (LAST) (FIRST) Molly Cavanaugh Section Number , Natalie Gassman - Jenny Lockard Kim Miller Will Molenkamp Alex Smith QUESTION NO. CREDIT SCORE lN§TRUQTIQN§ 1. There are three questions. Answer each in the speee previge d; you may write on the backs of sheets if you need more -room,{ but no loose sheets of paper will be accepted. Your Work must be clearly gamed and mm; credit will not be given for unintelligible responses. Metheg er reegning must be shown tor all computational items; no credit for merely putting down an answer, even it correct. Make sure that all answers have the appropriate number of significant tiggree. Give Mfor all answers, unless dimensionless. Open book examination. Any written 0r printed materials may be used. ‘ . DO NOT LIFT THIS COVER SHEET AND BEGIN WORK UNTIL INSTRUCTED TO DO SO! gee the fellewing gete if neegeg: H 1.008 O 16.00 Na 22.99 CI 35.45 Cr 52.00 Br 79.90 .03..” N979"? He 4.003 F 19.00 Mg 24.30 At 39.95 Fe 55.85 Ag107.87 .C 12.01 Ne 20.18 8 32.06 K 39.10 Cu 63.55 Cd112.41 N 14.01 Ca 40.08 Zn 65.39 v I 126.90 NA (Avogadro's Number) = 6.022 x 1023 Photon energy (Planck Law): 8 = hv = hc/7t. c(velocity of light): 3.00 x 108 ms1 . h(Planck's Constant) = 6.63 x 1034 J5. Bohr formula: En = -2.178 x 1013 J (ZZ/n2) ' 1 e.v.(electron volt) = 1.60 x 10-19J Coulomb energy between two charges 01 and 02;: E0 = 2.31 x 104.9 J nm(Q1Qzlr) (Q in multiples oi the elementary charge) The Wand algglam are on the back of this sheet. CHECK TO MAKE SURE THAT THIS EXAMINATION PAPER HAS THREE QUESTIONS AND FIVE PAGES _ -2; 14A2W02-2 ' - Name 1. (35 points) Below is a phase diagram for a pure substance X. For this problem,a|| pressures are expressed in atm. 1000 , , . . . . . . . . - . 100 ........... .......... .......... ........... ........... ........ ........... ............. ...... .......... ,,,,,,,, I. rrrrrrrr ________ ,7 1O PRESSURE IN ATM 101-.;;:2:ra-_ 200 225 250 275 300 325 350 375 400 425 450 475 500 525 550 TEMPERATURE IN K (a) '(6 points) Label the quuid-solid—vapor triple point with a T amd the critical point with a C, and give the TEMPERATURE of the triple point L o and the TEMPERATURE of the critical point 7 (b) (10 points) From the phase diagram, give the following: 0 ~ '-the MINIUMUM PRESSURE at whicfh liquid X can exist at equilibrium ' I A’ -the EQUlLlBRlUM VAPOR PRESSURE of SOLID X at 200 K m 35111 -the applied PRESSURE at which liquid X will boil at 290 K . km -the 1-ATM (NORMAL) BOILING TEMPERATURE of liquid X 3 g :2 g -the TEMPERATURE at which solid X melts under 1 atm pressure gra K ( c) (5 points) Which is the gamer phase, the solid form of X or the liquid form of X? Give a brief explanation of your answer. mg 50L I j)! 5 "ya: “Mew/iv;- 777L£_ 6316655025 7977‘ cad/ES W7— WPéfiATVgE w/LL com/m “470/ D75 5009) 440 fly as MEL/fie '5 Fem/am: m Pfi/l/Sz‘E—K P/ffl-S'E /H/ wit/I225. ' (d) (5 points) A sa/rnsple 0 solid X is Infigfi’g pg sung: 10% aid temperature = 200 K. it is slowly warmed to 500 K at constant pressure. if any phase changes occur during this process, state what they are and give the temperature at which they occur. ' ‘ ONE; P/Myf OHM/m; OocUIZJ; 7915 92737445073 77 mwa 57’ Zévk’. (’7’le Ll £90 ID will I/EIcT‘j TD 9UP£2 CRITICAL FLU/3D Ago I/é 47511, 501’“ 77115 15 1+ Halt—DUAL» OHM/5g #57 A- P/fii—ra 77619415 I 7701/9 (e) (9 points) 1.00 mole of substance X is placed in a vessel at 200 K. Find the M'lNlMUM volume which the vessel must have to guarantee that all of theX remains in the vapor phase with no solid X formed. A-T’ 202/4) 77+; VFW”; 79265522ng fiscal? /5 M 4&7?» - 5» THE. Prawn/Ice: /A/ 7W, V5555; mpg—Mars.wa 77+); . , _ ~I -I ‘1’ VAN”; 7.751.— ; C/wMoL)(o.o8’w6LA—7MMM Id Xmld); A6200 7414-): /0 ‘5 #77" , -3- 14A2W02-2 Name 2. (30 points) (a) (15 points) A solution is prepared by dissolving 125.0 grams of ethylene glycol (C2H502, ' MW 62.1) in enough water to give a final total volume of 750. mL (0.750 L). The density of this Solution is 1.10 g mL-1. Calculate:_ . _ _ -the MOLAR concentration of ethylene glycol in this solution £25706 F1257 PM]? Mal/£5 0F sou/72: wmms: blilkmrl :2'0/ ML Mat/m Con/C. = 92.0: MoL ‘ r ' 0.7571. '. 245’“ -the MASS of this solution Mfiss : Damn“ x Vu um: = /./O rm" x737; Mb: 8.25 -the MOLAL concentration of ethylene glycol in this solution M555 0F (Mus/e: my; .. MY é a 7m 9’ MOLAL cad/6. : Z'OIML :287471 0.700A4l (b) (15 points) A vessel of volume 50.0 liters contains HBr gas at pressure :01 23 atm and temperature = 300 K. This gas is then dissolved in enough water to give a final LIQUID SOLUTION volume =10.0 liters. -assuming that the HBr is completely dissociated in solution to give H+ and Br- ions, what is the pH of the solution? (8 points) I py (0.03514 9.0L F/Zé‘l“ FIND Mom; 015 #64 . 47M” 3 R7 = (bnofmbmflflflwjhm) 50.2mm; S/NCE #64 (Magyar D/5Jocudr733,{J 41m Mlsoumm/ 30,252 MoL [H+]_~ 0/.0L0SEM6L. 3 0_OZS_DM P_/7L= ‘LDFM £%:J= -laF/00.OLTD ': 50 -Now 8.00 grams of NaOH (0.200 moles) is added to the HBr solution. I What is the new pH of the solution after addition of the NaOH? (Assume the volume of the solution stays constant at 10.0 liters.) (7 points) Olwo Moog; oF M4014 WILL (El/1631' U/‘m ddoo Mane; op 5L7: Lam/ml; o, 2 55 N L -mzw MJL : o. os’émz— 0? H7377» mag/17?, 7771/! [Hi]: WL sows-o M pg; 15600179; «AMMOMS‘O = 2,33 v 14A2W02-2 Name 3. (35 points) The equilibrium constant K (in terms of pressures in bar) for the W reaction , H20(g) + C(s) = _H2(9) + CO(g) _ is 1.36 at 1000 K and 18.9 at 1200 K. Use this information to answer the following questions. (a) (5 points) Is the reaction as written (reading from left to right) Miner—Mo or exothermic? Explain your reasoning bneflx. . ' l 5/4/66 K Noam—5 as u 17% 7: 3 9 LE, (mt/Hume; Pave/Pi THE Mafimga WWI ¢ WP/AM— #72601 LEFT To EM-fi-T. ' (b) (10 points) Find Kc, the equilibrium constant for the reaction above in terms of molar concentrations, at 1000K. /K= ((7)6ch (56W 57’) 7’9‘76 Oil-mm? 5 .725 Fm 77w K fi-c‘noab A01 / I 4mg 0,.695 (MM WIDE)- me/v K =£T kc . AT mm x, , ' il<’= /,3é WWXWQQ . 7 ’ l-Moarl L ‘efl'fl—M u ~ ' Kc 3 £133.51 ’0'0/M ( c)(10 points); A vessel contains some solid C, H20(g) at a pressure of 0.240 bar, H2(g) at a pressure of 0.600 bar and CO(g) at a pressure of 0.800 bar at 1000 K. Is the system at equilibrium with regard to the reaction above? If it is not, will the amount of solid C in the vessel increase or W as the reaction proceeds to equilibrium? .EmLurrTE KéfiV/flfl’l/ QUOTIW : 6?; (gxgg; , ngw P (0.2 (4%”) . )WWW Smog 6? > K CI / .7: £4“; away/am) 1 4A2W02'-2 Name 3. (Con’t.) ( cl) (10 points) If you start with only solid C and some H20(g) in a vessel and want to convert the largest * amount possible to products, H2(g) and CO(g), at equilibrium, v -should you adjust the temperature to be as mgn as possible or as 1911 as possible? Afi let/HA A5 fox/5.4:: -should you make the volume of the vessel as Jarge as possible, as small as possible, or doesn’t it matter? fl’§ Lit/Ma +5 Wax/84a ixplaiuyour answers ' * - _ _ bpac 5/4/65 was K Flori/oz; P017067W/ &F 754/5 :18 T75) H A111) (0 Am; A450 5/4165 K /A/¢/2545£5 Mr l+ J L ) ' 3£#;Aup(dz,. #IkH T 'FAme; PEJ Duc‘Wu p 75 LA C/r‘e‘TEL/E/z fire/Alana mamas m1 5mm Mme éQU/L/ 32mm 75 [/25 ca 115 5 A5 Pass/845 ,2 4,, MP (9. A’cobzy/U VOLUME FAWflj .g-éA/EIZAW/ A5 MM” at? A“ n‘eA/cp were; VMUME FA mag/Demumow ...
View Full Document

This note was uploaded on 02/08/2012 for the course CHEM 14A 142042200 taught by Professor Lavelle during the Spring '10 term at UCLA.

Page1 / 5

key_mid2 - -1- 14A2W02-2 Baur CHEMISTRY 14A LECTURE SECTION...

This preview shows document pages 1 - 5. Sign up to view the full document.

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