NO._______________ SEAT PROF. JOHN VERKADE SPRING 2008 THIS EXAM CONSISTS OF 13 QUESTIONS ON 8 PAGES GRADING PAGE Page 2 Page 3 Page 4 Page 5 Page 6 TOTAL POINTS 21 pts 23 pts 24 pts 16 pts 16 pts 100 pts ________ SCORE ________ ________ ________ ________ CHEM 164 HOUR EXAM II FEBRAURY 27 NAME______________________ RECIT. INSTR._______________ RECIT. SECT.________________
NOTE: SHOW ALL OF YOUR WORK ON THESE EXAM PAGES. PUT YOUR ANSWERS IN THE ANSWER SPACES. THE LAST PAGE CONTAINS A PERIODIC TABLE AND USEFUL INFORMATION. THIS SHOULD BE REMOVED AND USED FOR REFERENCE AND SCRATCH PAPER. DO NOT PUT ANSWERS ON THIS TEAR AWAY PAGE.
READ THIS CAREFULLY BEFORE STARTING YOUR EXAM! Calculators are not required and they are not to be used. They are to be out of sight. For problems asking for calculations, just set up the problem but DO NOT solve for the answer. PLEASE NOTE that in setting up the problem, you do not need to isolate the unknown. Any calculations, such as summing atomic weights to obtain molecular weights necessary to solve the problem, can be left unsummed numbers, but identify them with a letter (e.g., y or z) as an unknown. All electronic devices (e.g., calculators, cell phones) and papers (except your test) are to be out of sight. All books, book bags, jackets, caps, hats, etc. are to be UNDER your seat. Please refrain from conversation from now until you leave and are outside the door. Thank you! The Staff appreciates your cooperation.
Teaching Assistants and Recitation Sections Name Sections Time Alex Belianinov 2, 3, 8 10:00, 11:00, 2:10 Sally McIntyre 1, 4, 6 9:00, 12:10, 1:10 Ryang Kim 7 2:10
THE ANSWER KEY TO THIS EXAM WILL BE POSTED ON BULLETIN BOARD #2 IN THE HALLWAY EAST OF ROOM 1002 GILMAN AND ON THE CHEM 164 WEBSITE.
2 1. (5 pts) Problem 13.6: Nitric oxide reacts with oxygen to give nitrogen dioxide (all gases); an important reaction in the Ostwald process for the industrial synthesis of nitric acid: 2 NO(g) + O2(g) 2 NO2(g)
If Kc = 6.9 105 at 227 C, what is the value of KP at this temperature?
2.
(10 pts) Problem 13.22: A platinum catalyst is used in automobile catalytic converters to hasten the oxidation of carbon monoxide: Pt 2 CO(g) + O2(g) 2 CO2(g) Ho = -566 kJ Suppose that you have a reaction vessel containing an equilibrium mixture of CO(g), O2(g), and CO2(g). Will the amount of CO increase, decrease, or remain the same when: a) A platinum catalyst is added. b) The temperature is increased. c) The pressure is increased by decreasing the volume. d) The pressure is increased by adding argon gas. e) The pressure is increased by adding O2 gas.
3.
(6 pts) Problem 14.1: Write a balanced equation for the dissociation of each of the following Brnsted-Lowry acids in water. Also, what is the conjugate base of each acid? a) H2SO4
b) NH4+
3 4. (8 pts) Problem 14.6: The concentration of OH in a sample of seawater is 5.0 106 M. Calculate the concentration of H3O+ ions, and classify the solution as acidic, neutral, or basic.
5.
(8 pts) Problem 14.11: Calculate the pH of a solution prepared by dissolving 0.25 g of BaO in enough water to make 0.500 L of solution.
6.
(4 pts) Problem 14.26b, c: Identify the stronger acid in each of the following pairs: (please circle) a) H2S or H2Te b) HNO2 or HNO3
7.
(3 pts) Problem 14.27a, c: For the following reaction, identify the Lewis acid and the Lewis base. AlCl3 + Cl AlCl4
4 8. (15 pts) Lecture demonstrations: a) Write a balanced equation for the burning of sugar catalyzed by carbon (finely divided charcoal)
b) How and why the ammonia fountain worked (in 25 words or less).
c) In 25 words or less plus a balanced equilibrium equation, explain why the NO2/N2O4-filled tube became lighter on cooling in dry ice.
9.
(9 pts) Ch 13 lecture notes, slides 28, 33 and 47: Kc for the gaseous equilibrium below is 57 at 700 C. At a certain point in the reaction of hydrogen with iodine, Qc is 8. H2 + I2 2 HI a) In which direction will the reaction go to reach equilibrium? b) What would be the effect on the equilibrium of decreasing the volume of the reaction vessel?
c) What would be the effect on Kc of the action in b)?
5 10. (16 pts) Ch 14, slide 38: Consider the equilibrium below. 1. HCN + H2O 2. a) (3 pts) After number 2 above, give the second reaction taking place in this aqueous solution and give its equilibrium constant. b) (3 pts) Which reaction dominant? is (State why in 10 words or less). H3O+ + CN Kc = 4.9 1010
c) (10 pts) Say we have a 0.10 M HCN solution of HCN. Set up the problem indicating what would have to be solved for to get the following concentrations: [HCN], [H3O+], [CN], [OH]
6 11. (5 pts) Ch 14, slide 47: Calculate the % dissociation of acetic acid [HOC(O)CH3] if the initial concentration is 1.00 M and the concentrations of H3O+ and OC(O)CH3 are each 4.2 103 M.
12.
(6 pts) Ch 14 Slide 60: Let's say Ka for an acid HA is 104. Show how you would calculate Kb.
13.
(5 pts) Ch 14 Slide 63: Show with a balanced equilibrium equation why an aqueous solution of NH4Cl is acidic and circle the species directly responsible for its acidic pH.
7
ln k = ln A
Ea RT
14
! E / RT k = Ae a
Ka Kb = 10 G = Go + RT ln Q F = 96,500 J/Vmol PV = nRT For 1st order reactions: Rate = k[A]
K=
!
!
!
G o = nG o (products) mG o (reactants) rxn f f pH = log [H3O+] or pH = log [H+] + 14 # E &# 1 k 1 & [H ] [OH ] = Kw = 1.0 10 ln 2 = " % a (% " ( pH + pOH = 14.00 $ R '$ T2 T1 ' k1 S o = nSo(products) mSo(reactants) rxn [A]t E a " T1 ! T2 % H o = [cH o (C) + dH o (D)] [aH o (A) + bH o (B)] rxn f f f f $ ' ln = kt = [A]0 R # T1 T2 & 0.0592 V Eo = log K ! cell n ln [A]t = kt + ln [A]0 Go = RT ln K KaKb = Kw 0.693 n" t1/2 = Go = nFE o R = 0.082 Latm/Kmol d= cell k 2 sin # nd "#H o q For 2 order reactions: sys S o = Eo = Eo Eo Ssurr = sys surr cell cath anode Rate = k[A]2 T T 1 coulomb = 1 ampsec G = G + RT ln Q 1 1 G = H TS ! = + kt proton mass = 1.007825 amu G = Wmax y = mx + b [A]t [A]o neutron mass is 1.008665 amu S = k ln W ! ! ! ! ! ! amu = 931.5 MeV 1 E = (m)c2 1 "H o t1/2 = T= o speed of light = 3.00 108 m/s 1V = 1J/C k[A]o "S 1.00 kg = 6.022 1026 amu 1A = 1C/s E = mc2 h = 6.626 1034 Js RT 1 J = kg m2/s2 Ecell = E o " ln Q cell c = 3.00 108 ms1 E = H PV nF 2 2 ! 1 J = 1 kg m s 0.0592 V R = 8.314 J/molK 1 Faraday = 96,500 Coulombs Ecell = log Q E = h n = c 109nm = 1 m 0.0592 V 760 torr = 1 atm log K ! Ecell = 4.18 J/g C 12 10 pm = 1 m n Avogadro's Number = 6.02 1023 Kw = 1.0 1014 102 cm = 1 m ! c = 3.00 108 m/s P = Xsolvent P o solvent "1312 H = $ "H o (products) # $ "H o (reactants) 1 N = 1 kg m/s2 f E= in kJ ! f 2 2 n 1 Pascal = 1 N/m H = # BE(broken) " # BE(formed) PA ! "b b 2 " 4ac = XA x= "2.178 # 10"18 PT 2a ! E= in J/atom ! n2 W = -PV dRT ! Hsoln = Hlattice + Hhydr of the ions = molar mass E = q + w P Sgas = kH Pgas H = E + (PV) ! Tb = Kb m Tf = Kf m P1V1 P2V2 q ! = C= n nT1 nT2 "T = solute RT = MRT = mol...