165Exam2KeyS08

165Exam2KeyS08 - DR. JESUDOSS KINGSTON CHEM 165 NAME A “5...

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Unformatted text preview: DR. JESUDOSS KINGSTON CHEM 165 NAME A “5 0027 SPRING 2008 HOUR EXAM 11 FEBRUARY 27, 2008 RECIT. INSTR. THIS EXAM CONSISTS OF 14 QUESTIONS ON 7 PAGES RECIT. SECT. GRADING Teaching Assistants and Recitation Sections PAGES POINTS SCORE Name Sections Time Page 2 18 pts Philip Carlson l, 13 9:00, 3:10 Emily Hull 6, 12 2:10, 3:10 Page 3 20 1’“ Aaron Kempema 10, 11 1:10, 2:10 Page 4 24 pts Gerald Pollock 4, 5 12:10, 1:10 S l 11 10: :0 Page 5 22 pts 6 ena Russe 8, 9 00, 11 0 Stephanie Smith 2, 7 10:00, 9:00 Page 6 19 Pts Justin Valenstein 3 11:00 TOTAL 103 pts Rules for the Exam: 1. Show all of your work on these exam pages. Numerical answers should be given in the correct number of significant figures and units. Put your answers in the answer Spaces. 2. The last page contains some useful information and a periodic table. l. (4 pts) Which of these indicates stronger intermolecular forces in a liquid? a) a low surface tension b) a low AHvap a low vapor pressure (4 pts) The compounds Br; (bromine) and ICl (iodine monochloride) have almost the same molar masses, yet Br; melts at —7.2 0C, whereas 1C1 melts at 272°C. This is because c) a low boiling point e) a high tendency to flow a) Br; is brown and absorbs more light energy, causing it to melt at a lower temperature. b) The standard enthalpy of formation of an element is zero; 1C1 is not a pure element but rather a compound. c) The intermolecular forces are higher in Br; than in 1C1. d) ICl has higher electonegativity than Brz. 1C1 is a polar molecule possessing stronger intermolecular forces than Brz. (4 points) Which one of the following can form hydrogen bonds with other molecules of the same kind? Circle a_ll that apply. (F or wrong answers, points will be taken off) a) HCOOH Refer to the phase diagram of a substance to answer the following m questions. b) CH3CH2-O-CH2CH3 Hm @CH3CHZCHZOH ©CH3COOH 1.5 — (A) (3 pts) The normal boiling point of this substance is approximately 0C. P(atm) 1.0 AL - a) —10 b) 0 c) 15 0'5 ‘ d) 25 .30 f) 40 | i I l i r g) 45 -10 0 10 20 3O 40 50 T (0C) (B) (3 pts) Identify a region/segment of the phase diagram that corresponds to the conditions of temperature and pressure under which both the solid and gaseous state of the substance‘are in equilibrium. on) g) At Point Z a) AB b) AC D At point Y d) At point A C) At point X (10 pts) For the reaction NO(g) + 03(g) 9 N02(g) + 02(3), the following experimental data were obtained. Which one of the following represents the correct rate law for this reaction? 1' m a) Rate = k [N0]4 [03]8 b) Rate = k {N0}3 [03]2 0) Rate = k [NO] [03]2 ate = k [N0]2 [03]3 e) Rate = k [NO] [03]3 1) Rate = k [N0]2 [03] (10 pts) The rate law for the reaction NH4+(aq) + N02‘(aq)—-——> N2(g) + 2H20(l) is given by rate = k[NH4+][N02_]. At 25°C, the rate of the reaction was found to be 6.3 x 10—6 M/s. Calculate the numerical value of the rate constant (k) at this temperature if [NI-14+] = 0.26 M and [NOf] = 0.080 M. (Show your work for full credit and report your answer with proper units) Rafi :2 K [N [Moi—j tamaémé‘ 2—. K [O-aemflo'osoMi Theveféve, K .2: -4, -f *’ .2: 3. S (10 pts) Propane is three-carbon alkane (C3H3) and it is normally a gas at room temperature. It is commonly used as fuel for engines, barbecues, and home heating systems. In the presence of oxygen, propane burns to form carbon dioxide, water and heat as shown below: C3Hg(g) + 5 02(g) 9 3 C02(g) +4 H20(g) + 2500 BTU If the rate at which oxygen consumed is 4.2 x 102 atm/hr, what is the rate at which carbon dioxide is produced? ( Show your work for full credit) inen M, 4 a?) : 4.2mm;1 aim/h Basal 0n Hm Smckomtg/ wig Can (Mufti, ... 5032] A {(021 3 3 at} lxfirlwo ak/ . aka 3 4310 Z" 5 9‘ - “- fl-[SH-Ei ‘: Answ/A (14 pts) Calculate the boiling point and the freezing point of the solution containing 478 g of ethylene glycol (FW = 62.01 g/mol) in 3202 g of water. [The normal freezing point and boiling point of water is 0°C and 100°C respectively. For water, Kb = 0.520C/rn; Kf = 1.860C/m; density = 1.0 g/mL] AT : K .m M I M00143: MM : 4783x6133 ___ 7-703mgl K3 00‘ Soil/W 3.20.2 K3 3.102 k3 :2 (2.407”, New, 511,:in C/m)(2.407m) 5Tb; : Wm . S ['3 C a 20.86 °(/M)(2»4-O7m) '3 Tb ~ [cont/~15 : l01~3C : +48% Boiling Point: I ’3 °C Freezing Point: “4“4’8 0C 9. (8 pts) What kind of attractive forces (list all that apply) that must be overcome to a)boilliquidNH3 : Bomb/Ig- z Lagéfl :Di‘SPBYSlO‘I’l b)rne]tice : HgoLrvggn Bonding, LQndQn ®iSPQTSi0n c)boilliquidBr2 : (211% Lflflifln Bt‘segTS‘t'an :Mflmdflamohdw Fora: d) dissociate F2 to F atoms 10. (8 pts) Kevlar is a copolymer used in bullet-proof vests. It is formed in a condensation reaction between the following two monomers (A and B). Write the overall chemical equation for the condensation reaction. (show the repeating monomer unit and byproduct(s) if any). H0004C>7000H HflQ‘NHZ Terephthalic acid (A) 1,4—diamino benzene (B) 0 O H / \ ~ N @— N ... I l H H n 11. (6 pts) Draw a diagram to show the hydrogen bonding of methanol molecule with two other methanol molecules. if i . H—C— 0 ~ H H “ * *— 0” H ‘ H 1+ H I H (-3—.- I I r-s C3 ii I \ I'llnnrOlH'“ r“? I I ln 1; I: O 31‘ :1: L—AJ \ C? a..— 6 12. (8 pts) Deduce the plausible monomers for the polymer with following repeating unit: i l T T C—QC%O—T*T*O H H n \Z s, 0 l? “ @ C~OH . 1 H04: Hoary—CH“? OH TMchMc acid 65 Cd 13. (8 pts) Enthalpy change associated with the phase changes of water can be related by Hess’s Law with some approximation. Estimate the enthalpy change (in kJ/mol) for the condensation process, H20(g) —> H200) given the following data: fl H20(s) 9H20(g) AHsub=46.81kJ/mol 3" GI '9 L 1120(5) 9 H200) AHqu = 6.01 kJ/mol AHSULJ :: MAW, 7,. +5.31- 6,01 .-.-. 40.30 kJ/mol ‘ " AHCOndlnSotW : .— : $4.0“ 80 Ans. 14. (Extra Credit! 3 pts) Which one of the following will have higher AHvap? H3NH2 b) CH4 C) CH2=CH2 d) SiH4 6) H28 ...
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This note was uploaded on 03/26/2008 for the course CHEM 165 taught by Professor Kingston during the Spring '08 term at Iowa State.

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165Exam2KeyS08 - DR. JESUDOSS KINGSTON CHEM 165 NAME A “5...

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